Page 1


Contract

NO.

W-7405-eng-26

METALLURGY DrVIS I O N

COREOSION ASSOCIATED WITH FLUORINATIOW I N TI-E OAK RIDGE NATIONAL LABORATORY FLUORIDE VOLATILT'

PROCESS

A. P. L i t m a n and A. E. Goldman

OAK X I E E NATIOT\IAL LABOMTORY Oak Ridge, Tennessee o p e r a t e d by UNION CARBIDE C O W O M T I O N for %!le U. S . A'l'OMILC ENERGY COMMISSION

3 445b 0363460 3


ii i

CON'ER'L'S

1.

B.

5 5 6

C.

12

A.

12

16

21

D.

25

25

25

31 32

35 37

IT.

Mark II V o l a t i l i t y P i l o t P l a n t L Nickel Fluorinator------------

A. B.

c.

37 40 40

41 44 44 49 5151

D.

62 62 67

P

69 '70

70


iv

'7 1 '77 79 '79

80 84

84 89

95 95

96 3-08 108 113

13-3

119 i23 125

125

126 129

129

130

1-31 153 3-55 159 166 1'13

174


CORROSIOPJ ASSOCIATED WITH FLUORINATION I N TEE OAK RIDGE NATIONAL L4BORriTORY FLUORIDE V O L A T I L I T Y PIIOCESS A. P. Litmsn and A . E . Goldman

T h i s r e p o r t e v a l u a t e s chemical c o r r o s i o n on r e a c t i o n v e s s e l s and equipnient used dul-lng t h e f l u o r i n a t i o n of fused-salt f u e l s a n d su’oseciu.ent, a s s o c i a t e d o p e r a t i o n s i n t h e Oak liidgc Ndtional Laboratory (ORNL) F l u o r i d ? V o l a t i l i t y Process and i s a c o n t i n u a t i o n and expansion o f the Metal-lurgy

D i v i s i o n assistance t o t h e Chemical Technology D i v i s i o n i n -this regard

The f l u o r i n a l i i o n phase c o n s i s t s o f c o n v e r t i n g uranium t e t r a f l u o r i . d e t o

volatile uranium liexaf luoride b y fl u o r i n e s p a r g i n g of molten f l u o r i d e s a l t s and s u b o e q w n t d.ecoritamination and recovery o f the uranium h e x a f l u o r i d e .

For convenience i n r e p o r t i n g , t h i . s document i s d i v i d e d i n t o s i x s e c -

tions.

S e c t l o n s I and, I1 d e s c r i b e t h e corrosi-on behavior o f Yull-size

f l u o r i n a t i o n v e s s e l s fabricated fr-om I, n i c k e l and used d u r i n g Vo1.ati-lity

P i . l o t P l a n t (WY) o p e r a t i o n s .

S e c t i o n 111 covers c o r r o s i o n e v a l u a t i o n s OY

bench-scale f1uorinal;or.s made o f A n i c k e l , Liiconel, and INOE-8, which w e r e o p e r a t e d by t h e V o l a t i . l i t ; y S t u d i e s Group, Chemical Development

of t‘ne Chemical Technology Division.

S e c t i o n A,

S e c t i o n I V describes s c o u t h g tests

of many p r o p r i e t a r y and n o n p r o p r i e t a r y m a t e r i a l s exposed t o t h e p l l o t

~1mi-l

f l u o r i n a t o r environments and the r e a c t i o n s o f t h e v a r i o u s materi.als t o

those s e r v i c e c o n d i t i o n s .

Appendix A shows s e l e c t e d photomicrographs of

t h e c o r r o s i o n specimens d e s c r i b e d i n S e c t i c n I V .

For comparison, r e s u l t s

of some oT t h e coi-rosi-on t e s t s performed by t h e Argonne N a t i o n a l Laboratory

on metal coupons under s i m u l a t e d f l u o r i n a t i o n coriditions are r e p o r t e d i.n S e c t i o n V.

S e c t i o n V I arid Appendix B deal w l t h r e s u l t s of examinations o f

supplenientary VPP equipment i n c l u d i n g a r a d i o a c t i v e - p r o d u c t s t r a p , a

waste-salt l i n e , t h e a b s o r b e r s , v a l v e s and f i t t i n g s , t h e f l u o r i n e - d i s p o s a l system, and process-gas 1Ines.

I n t h i s r e p o r t , c o r r o s i v e a t t a c k i s r e p o r t e d as m i l s p e r month ba,rd

on molten s a l t r e s i d e n c e t i m e o r mils p e r hour based on f l u o r i n e exposure


time.

These r a t e s a r e incl.uiled s p e c i f i c a l l y l'or coiaparison Fta-poses, a r e

n o t e x a c t , and s h o u l t 3 n o t be e x t r a p o l a t e d i i i t o longer Lice periods Tor design

WOi-:i

c r o t h e r applicaiions.

Tvo f l u o r i n a t o r s were iAsed i n the W P t o c a r r y out t h e T l u o r i n s t i o n

reacti~ons. Tlicse ve:;sel.s, Mark 1 a n d Mark T I , were fabr-i.cated -into 'I c;,l-i.ncYcr:;, nicliel.

apy,rox L.-l/'2

f'L .in h e i g h t ,

f r o x tlie szme lient oi' L (low c a r b c p )

Tlie f i r s L vessel. c c ~ n t a i n e dequiiiiclar ThF-ZrE,

or MaF-7~~~F, -UFjL

1 1

(b&!k&--!t illole

57 500

0 ~ 7 ~ 5 "over ~ .a

$) f o r approx 1250 h r a t

perioci

s t a n d a r d 1.liters oi' F, were suarged i n t o -ihe s a l i s .

4-

01'

161

iir,

T h i s coiictiiuLec

a F .U no1.e r a t i o of 3: 1 beyond t h e o r e t i c a l . reipii-emeri-Ls. The Marl: 11 2' fluorinator contained- f l u o r i d e s ~ 1 . ot f~ a p p r o x i m a t e l y the same c c m p o c i t i o n s

plus m a l l a d d i L i o n s oi' PLIF)~ dL;l-i.ng

at

5 l C c ~ ; j o ~i'or c

t h r e e runs.

The r , a l t c were liegt :noltcn

approx 1950 ilia and aboitt CO 500 s t a n d a r d liters oi Fp>vere c

sparsed i n t o the Mark T I m e l t s in 92 h r . Bot.!i f l u ~ o r i n a t o r ss a s t a i red

s i v e .wall t h l r i n i ng.,

severe‘

larce

corrcsior: l o s s e s c o n s i s t i c ; ;

0;'exten-

i n t c r i o r j-ntergi-anular a t t a c k , and a moueri;-te

e s t e r i o r oxidstion attack.

Maximum d e t e r i o r a t i o n on t h e Mark 1 vessel oc-

c u r r e d i n %lie middle vapor r e g i o n a t a calculai,ed rate o f 1 . 2 m i l s / h r . ,

on Ylcorine sparge time, o r

ten sal-ts.

46

m i l s / r c n t h , based on time o f

expoS1Jj:C

'us:;ed

t o niol-

The second v e s s e l showed maxi mum a-ttack i n t h e sal.t-con.iai n i n z

r e g i ~ o nat, s i m i l a r l y cal.cu1ait.d r a t e s o f I.1 t n i . l s / h r and 60 mjLls/month.

Some

evidence was found -to j n d i c a t e that, the intergrai?iilar r,'i,tack may iwve r e s u l i e i j

â‚Źrom sull'ur i n ~Lhe sys'ce:::~.

BUl.1: metal losses Yron the vcssel.'s walls x r e

b e l i e v e 6 t o be t h e resuJ.t of cyclic l o s s e s o f IViF " ~ r o t e c t i v ~film:;. " '!The 2 f i l m s were Tormed on t h e i n t e r i o r walls o f the i'l.uorinators during conGitioni.ng and f 1uoririati.on tree~ir::ents and 3.ost as t h e result oi i-upt;lring, spbl.ling, , ' l u x i n g , washing a c t i o n s , and/or d i s s o l u t i o n i n higi-L1.y c o r r o s i v ~concknsa-tes lorincd during opera+.,i.ons. The s h i f t i n rnaxiniun c o r r o s i o n a-l;Lacl; gcouiciry

i n t h e two f l u o r i n a t o r s i s beli-eved to have r e s u l t e a f r o m diyfererices i n

opera-1;: ng cond7-tlons.

The Mark 11 v e s s e l experienced hi;r,her LeriperaLures,

longer fluorine exposure tinies, and extended uranium i-esidence times i n iLts salt baths.


Speciinr-ns removed from t h e w a l l o f t h e Cirst i ' l u o r i n a t o r showed. a

v a r i a t i o n i n average MTM g r a j n - s i z e number o . ~ ~6 he:i..izg i?ound In t h e n1Ldd.k vapor reggion.

t o > 1, WE l a r g e s t g r a i n s

Tlne second. v e s s e l had a more uiiiforrn

grain-si ze pa-Ltern, average ASYM g r a i n - s i z e nurribers v a r y i n g from

-3-5

~ 4 .

to

T'ne v a r i a t i . o n s i n g r a i n sizes a r e b e l i e v e d t o have r e s u l t e d from v a r i a b l e

heati.ng rates d u r i n g i n i t i a l usage. stxess recovery

Low rate:; permit more complete i n - t e r n a l

pri.or t o the star-L o f r e c r y s t a l l i z a t i o n whl.ch results i n

fewer r i u s l e a t i o n s i t e s and t h e r e f o r e lalager graj-ns during r e c r y s t a l l i ~ , : a t i o n .

Metallographic examinations d i d n o t provide evid-ence of a cau.sal r e l a t i o n s h i p between grain s i x arid f l u o r i n a t o r wall c o r r o s i o n .

Exnm.inations of bene h- scale r e a c t o r s , vhe re s l m u l a t e d f l u o r inati on

env-ironment;7 were provided t o s t u d y p r o c e s s v a r i a b l e s and c o r r o s i o n , shoved i l i . a t A n i c k e l had 'the h i g h e s t degree oi' c o r r o s i o n r e s i . s t a n c e as a rluorina-Lor

materi.a.1 of constructj.ori when. coinpared. with I n c o n e l and INOR-8. I n t e r g r a n u l a r

penetration arid subseqiien-t sloughing or" whole gmi.ns seerned

dominant mode of' corrosive a t t a c k on the I n c o n e l vessel.

.to be t h e pre-

A t t h e higher t e a t

temperatures, 600째C, INOR-8 i n i n i a t i ~ r ef l i i o r i i i a t o r s shoved lar.ge b u l k metal

l o s s e s plus select-ive l o s s e s o:C chromium, molybd.enum, and iron from t h e exposed. a l l o y su-rfaces.

EvId.ei-ice of a mzrlied r e d u c t i o n i n a t t a c k on ni~ckeland

450-525"C.

was found d a r i n g lower terripera-tiu*es t i t d i e s a t

INOR-8

These lower tempera-

t u r e ope r a t i o n s were made p o s s i b l e by adding 1L-Lhium f l u o r i d e t o t h e sod.j-~i:m f l u o r i d e - zirconi.um tetrar"luoi-i.c3.e s a l t mixtures. Scouti.ng corrosiori t e s t s w e r e performed

j

n t h e VPP's fluorina-Lors using

rod, sheet, or wire specimens of e o m i e r c i a l and. developmental alloys. b e s t s were siibjectt?d Lo s e r i o u s l i m i t a t i o n s du.e t o t h e

'These

lack of control over

o p ? r a t i n g c o n d i t i o n s arld thus c o n s i d e r a b l e va-ri.ation i n Lhe c o r r o s i o n of I,

n i c k e l c o n t r o l specimens r e s u l t e d

and. cobal.1; showed some s u p 1, n i - c k e l specimens

e

and c oba l i Cluori d-e:s

Those

iii ckrel-

r i c h alloys containi.ng i.ron

i.ori.ty -i n c o r r o s ion r e s i s t a n c e when conqiired -w.i.th

"his was p r o b a b l y becai.l.:;e of the low v o l a t i l i t y o:? i.ron

.

n i l c ke 1-ri eh a1loy s e o n t aining ino lybd e num add.it i o n s

showed v a r i a b l e bzhavior i n the i'lu.ori.nai,i on erivironment. sug;i'esl;ed.

Some of the data

i.mprov-ed r e s i s t a n c e 0-ver L riickel while o t h e r t e s t s showed tile r e v e r s e .


-4Since b o i h o f t h e k n o w molybdenum f l u o r i d e s Lhat could be formed a u r i n g

Y l u o r i n a t i o n have v e r y h i g h v o l a t i l i t y , one would not expect inrproved r e s i s t a n c e

from molybdenum a d - d i t i o n s .

Tne experiments emphasize t h a t t h e p r e s e n t method

o f s e l e c t i o n O P test m a t e r i a l s based on t h e OW v o l a t i l i t y of metal fluorides

t h a t may f o r i n during C h l o r i n a t i o n c o n t i n u e s t o have m e r i . 1 .

A d d i t i o n a l ex-

pe r i m e n t a l n i cke 1.-base a 1l o y c o r r o s i o n specimens , c o n t a i n i n g riiagne s i u m , alumi num, iron, c o b a l t , o r manganese, have been fabri.cated and w i l l be used i n fui?xre s c r e e n i n g t e s t s i n a subsequent p i l o t p1an.i; f l u o r i n a t o r . A review o f one Y l u o r i n a t j on t e s t s e r i e s conducted. by t h e Argonne

Nat i-onal Laboratory gave g e n e r a l agr?ement wj.th ORNL s c o u t i n g c o r r o s i o n Lest specimen r e s u l t s , al.thougii comparisons were hampered by d i f f e r e n t t e s t con-

.

di-tions

The Argonne Nat,ional- Laboratory has suggested t h a t t h e corrosrion

probI.em be a t t a c k e a by I l r t h e r s t u d i e s on t h e use of c o l d wall vessel...;,

spray

towers, or 1.ow-metti ng s a l t s f o r vel-atility p r o c e s s e s .

Visus.1 am? metallographic examinations p l u s u l t r a s o n i c measurements of

o i h e r VPP v e s s e l s and equipment i k b r i c a t e d g e n e r a l l y I’mm Monel. o r l n c o n e l

showed a wide v a r i . a t i o n i n r e s i s t a n c e -bo t h o s e v a r i o u s l o c a l s e r v i c e c0nd.itions.

The s t u d i e s suggest t h a t l n c o n e l can continue t o be used a s a m a t e r i a l

o f construction f o r some components b u t f r e q u e n t i n s p e c t i o n s a r e indicated..

Monel ayjpears g e n e r a l l y s a t i s r a c t o r y f o r t h e applilcations t o d a t e .

From a corrosi-on stand~poi.nt, the € l u o r i n a t i o n v e s s e l i n t h e VPP continues t o be t h e most v u l n e r a b l e t o a - t t a c k due t o t h e n a t u r e of t h e con’iaiLned vironixent and t h e high temperature necessary f o r f l u o r i n a t i o n .

en-

The continued

use of L n i c k e l f o r t h c fln.orina-kion vessel. d e s n o t appear p r o b i b i i i v e f o r batch. o p e r a t i o n s only di2e t o t h e p r e s e n t h i g h value of t h e p i l o t plai-1.l;’~ product.

A-t p r e s e n t , the only guarantee f o r jrnproved s e r v i c e l i f e Cor n i c k e l

f l u o r i n a t o r s seeins t o be u t i l i z a t l o n of the lowest p r a c t i c a l temperature *

Although not conclusi.vely proven f o r t h e f l u o r i n a t i o n v e s s e l s , i-eduction o f

s u l f u r contami.iiation and t h e e n s u r i n g OC a unifo-mi, smal.l--grai i l si..,e i n t h e

v e s s e l s may improve v e s s e l p e r f o m a n c e .

or long-iziine f l u o r i n a t o r i.ntcgrj.ty,

s e l e c t i o n o r development o f a new material of c o n s t r u c t i o n , the use o f s a l t s

with losrier m e l t i n g points, or the use o f a c o l d wall vessel., seems necessary.


The e v a l u a t i o n of p r o c e s s c o r r o s i o n t h a t occurred druring the d.eveI_op-

menl; s t u d i e s of hyd-rogen f 1uori.de d i s s o l u t i o r i of u.raniiim-inear.lng f u e l elements, tile head.-end cycle of t h e v o l a t i l i t y process, wri..LI be covered i n a separa-Le

report.

1

I. Mark I V o l a t i l i t y P i l o t ; P l a n t L Nickel. F l u o r i n a t o r M a t e r i a l S e l e c t i o n and F a b r i c a t i o n

A.

I__

T'ne s e l e c t i o n oi' riiaterial f o r t h e f i r s t p i l o t pl.ant Yluor'inator was

made by members of the Chemical Technology L).i.vision afte.r a s t u d y of the avai.1-

a b l e corrosi-on l i t e r a t u r e and t h e AS&% B o i l e r and Pressure Vessel. Code.

2, 3 ,J-1

Nickel seemed t o be t h e most l i k e l y eandiclate material o f c o n s t r u c t i o n , adltliough

a t 600-700째C,

t h e a n t i c i p a t e d o p e r a t i n g ternplirzture range o f the f l u o r i n a t o r ,

Myers and. IIeI.org repported p e n e t r a t i o n rates of f l u o r i n e on nickel. o f 16-34 mils/rnonth.

The ASME Code all-owable d e s i g n s t r e s s dat,a above approx 31.5"C

were n o t available f o r commercial p u r i t y A n i c k e l ( O . O > O . l 5

brl;

$

C).

This

was because of the known e f f e c t s of enibrittlem.ent through i n t e r c r y s t a l l i r i e

p r e c i p i t a t i o n of g r s p l i i t e i n nickel c o n t a i n i n g carbon af-Ler l o n g - t l nie exposure

t o h i g h tetnperatures.

However, s a t i s f a c t o r y d e s i g n data were a v a i l a b l e f o r

low-carbon L n i c k e l at, approx 650"c,so t h i s material w a s s e l e c t e d Cor. -the f i r s t pilot p l a n t f1uori.nator.

'The Mark 7: Y l u o r l n a t o r w a s fabricated at ORPSL from 1, n i c k e l using

h e a t w i t h t h e vendor s a m l y s i s of

0.0416 Si-O.OO$

S.

1 L

I-_-_

Annealed p l a t e

8

99.36% Ni-O.O2$ C-O.2$ Fe--O.O6$ CIYO 26$ Mns t o c k of 1/4-1ns thjickness w a s r o l l e d i n t o

A. E. Goldnian and. A. P. Litmaa, Corrosl.oro Associated with iry-drogen Fliro??id.e D i s s o-l u t i o n i n the F l u o r i d e V o l a t j - l i t y Process ORNTJ-28:3:j (Lo b e p u b l i s h e d ) . --2 2

(May,

H. Myers 1948).

W.

and. W.

B. &Long,

"Fluorine Corrosj.on, " (:hem. Engr. Prog.

3ffEngineering P r o p e r t i e s o f Nickel, " Tech. B~11.T-15, T h e I n t e r n a t i o n a l Nickel company, Tnc., New York, Revised, p. 21, J u l y , lgh9. "'Rules f o r Constructi.on of U r i f i r e d Pressire V e s s e l s , ASME: B o i l e r arid Pyessu-re V e s s e l COIF;., S e c t i o n VIIT, .Am. Soc. Meeh. ~ n g . 15156 E < t - t i o i i . . __I

%I. A. &li.id.ge, "Xieke1 ami Rickel-Copper, N;Tri ckel-Msnganese, and. rielated Xt&t-N:i.ck.el Alloys, " The Corrosion iIai~.dbooli (ed.. by T I . H. Uhli.g), p . 683, John Wiley an.d. Sons, Iric., New .York, 19&3 ~


- 6 -

B.

Operational l l i s___.. tory

_I___

___I

r wac csed b;; tiic iiiiit O p r a t i o i i s Scc-kioii ai'

i;he Chemical '!i'ech:iolo~:y D i v i s i or. t u r i q;;,p i - e l i z i c a r y r'lcor.ination e q u Lpiwri-L s t u d i e s for a p e r i o d oI' aboilt, tliree m o r i i h s .

DLiri.c;: t h a t L i m e > , no i'li;cirine o r

uranium-contaii-iin~r-lol~tens a l t s were i n c o r i t s c t w i - L l i the v e s s e l .

Tu;: Le 1.

c i t e s the process c o n u i t i o n s i n deiai.1 fi:r those s t u d i e s 2nd â&#x201A;Źor t h e more

e x t z n s i v e "M"

e qui prnent slid<?down an6 "C I ' proce s s de mons tration ru~.inbLJerrorme d

l a t e r i n t h e VPP.

F i g i r e ? SilowS t h e position o f t n e Marl: T f l u o r i n a t o r during the W P

pJns while Fi~g. 3 shows tile i n t e r i c r pi.pLrLg, >;as d.ispersion asseillbl5, arid t h e

pLaccrnent or a n early groul>

01'

corrosion % e s t sgeciircns.

t h e fluorjfnaLion v e s s e l was surround-ed Is;; 1-,,,st,ance 0ci

8

Tile l o v e r ha1 i" oi"

v z r t i cal Lube-type e l e z i r i c -

fiirnace of 3 0 - l ~rating t o provide tlie necessary lieai (600--y25"c)

f o r operations.

During t h e pilot F l a n t r-ms, rod-type e l - e c t r i c r e s i s t a n c e

h e a t i n g elements w i i h a tubal rad,iI;g of t c r i o r walls oâ&#x201A;Ź t h e f l u o r i n s t a r .

3

Iiw were i n s t a l l e d on the upper

ex-

P r i o r t o exposing -tile f l u o r i n a t o r t o elerr-ental f I.uorine duriog actual.

f l u o r i n a t i o n o f t:ie fused salts, a "ccndi.ti onling" c y c l e was performed wherein

f l u o r j n e was inti-ocluced i.nto t h e vessel. %rliicn was h e a t e d io 2 0 - l ~ O " C t o

"protecti.ve'I f i h s . F l u o r i n e used Til t h e V~PP 2 was obtaaincd i n s t e e l tank t r a i l e r s Yrom t h e Oak Ri.dge CaseoGs D!'i'fusion induce t h e foraiai;ion o f Nil?

Plant ( ORGDP) f l u o r i - n c g e n e r a t i n g s t a f ,j-on.

A -il.owing stream sample analyzed

by OHGDP _.. p z r s o n n e l i n d i - c a t e d t h e a n a l y s t s o f t h e f l u o r i n e was

958 F2, < 5% W,

R. M. Evans (ea. ) I__..__.___ Oak Ridge Na'cional Lriboratory, R e a c______ tor Materials TID-IO17, pp, 117-128 w o b e r 23, 1-958).

-S . p .e c.i r i c a t i o n s ,


-7-

U NCLASS I F I ED PHOTO52707

i N C O N E t TOP F L A N G E I N C O N E L S L I P - O N FLANGE

Y4-in. L NICKEL S H E' L L __

d

SEAL

L I

-GIRTH %3/8-in.

WELD

L NiCKEL D I S H E D HEAD

Fig. 1. Mark I: Volatility Pilot Plant Fluorinatar.


Table I.

Process Conditions f o r Mark I V o l a t i l i t y P i l o t P l a n t F l u o r i n a (Unit Operations, V o l a t i l i t y P i l o t P l a n t "M" and "C" Funs)

Phase I Unit Operations Runs Temperature; m a x ("C) Thermal cycles (room temperature t o 600-725"~) Time of exposure a t temperature ( s a l t s molten-hr) S a l t composition (nominal mole $)

600-700

-

Phase I1 "M" Runs (1-48) 600-72 5

600-725

20

10

445

715

20

90

N

(- 30 w i t h N sparge)' (- 60 withou? N2 s p a r g e ) NaF-ZrF4 (50-50)

Phase I11 "C" Runs (1-15)

NaF-ZrF4 (50-50) NaF-ZrF4-UF4

Total 60~725

(d)

None

35 i n 14 h r

(48-48-4) 530 i n 0.5 hr

Operations fluorine input b (liters)

None

16 775

40

UF 6 exposure

None

None

Conditioning fluorine input (liters a

(hr)

10 h r

in

830 i n 5 1

-

20 h r

1250

565 i n 14.5 h r hr

57 500 i n 6 1 h r (7-33 l i t e r s / m i n )

-

20 h r

a

These o p e r a t i o n s were done a t 20-150째C f o r t h e purpose of inducing an i n i t i a l " p r o t e c t i v e " f i l m of n i c k e l f l u o r i d e on t h e w a l l s of t h e f l u o r i n a t o r .

bAn average of 3:1 mole r a t i o (F2:U) beyond t h e o r e t i c a l requirements w a s used i n o r d e r t o reduce t h e f i n a l uranium c o n c e n t r a t i o n i n t h e s a l t t o a few p a r t s p e r m i l l i o n , C

Top f l a n g e removed,

-5

hr.

% a l t s were used p r e v i o u s l y i n u n i r r a d i a t e d loop s t u d i e s and t h e r e f o r e contained s i g n i f i c a n t amounts of c o r r o s i o n products as shown below. Ref: C. L. Whitmarsh, A S e r i e s of Seven Flowsheet S t u d i e s with Nonradive S a l t , V o l a t i l i t y P i l o t P l a n t Runs, C-9 Through C-15, p. 10, CF-58-5-113 (May 12, 1958). Component: 0.08-0.18 w t $ N i , 0.06-0.10 w t $I C r , 0.01-0.02 w t $I Fe, 0.01-0.60 w t $ T i , 0.002-3.4 w t Si.

i

a3 I


N

N

11.

- 9 -

t-r

I

cu M


-

10

UNCLASSIFIED PHOTO 52706

THERMOCOUPLE W E L L

-9 ,

i ir

FLUORINE INLET L l L E

NITROGEN I N L E T LINE-

AVERAGE OF VA P 0R - SALT I N T E Rf ACES ( 3 5 in. BELOW S L I P - O N F L A N G E ) --+

DIFFUSER GONE

_ I

DRAFT T U B E

CO R R OS IO N S P EC I PA E NS

CORROSION SPECIMENS

s i o n Assembly, and Placement of the Mark I VPP Fluorinator.


-

11

-

and 1-2% N2 and/or 02. P r i o r to use of' t h e f l u o r i n e i n t h e WP, t h e gas w a s passed through a f i x e d NaF p e l l e t bed a t approximately ambient temperatures. Under t h e s e c o n d i t i o n s , t h e hydrogen f l u o r i d e content i n t h e Tluorine was lowered t o approx 20 ppm. ( r e f 7) A f t e r conditioning, t h e system w a s purged w i t h commercial grade nitrogen dried t o

<

1 ppm H20.

which w a s n o t removed.

T'ne n i t r o g e n contained approx 100 ppm 0,

-

The f l u o r i n a t o r w a s heated to approx 600°C along with

t h e s a l t f r e e b e valve and s a l t i n l e t l i n e . heated by a u t o r e s i s t a n c e .

The l a t t e r two component,s were

Then a b a t c h of € l u o r i d e s a l t w a s melted in t h e

charge melt tank and d r a i n e d by g r a v i t y flow i n t o t h e I l u o r i n a t o r . F l u o r i n e w a s bubbled through t h e molten s a l t t o convert an:/ UF4 in t h e s a l t t o v o l a t i l e uF6.

During f l u o r i n a t i o n , t h e v e s s e l o p e r a t e d w i t h

approx 25% of i t s volume f i l l e d with about maining

75%

50 l i t e r s of f u s e d s a l t s .

The r e -

of t h e volume contained v a r i a b l e q u a n t i t i e s of f l u o r i n e , uranium

h e x a f l u o r i d e , n i t r o g e n , and v a r i o u s metal f l u o r i d e s of high or interniediate volatility. of

During t h e process demonstration "C" runs, an average mole r a t i o

3 : l (F2 : U ) beyond t h e o r e t i c a l requirements w a s used i n o r d e r t o r e h c e t h e

f i n a l uranium c o n c e n t r a t i o n i n t h e s a l t to a €ew p a r t s p e r m i l l i o n .

While t h e v e s s e l w a l l i n t h e s a l t - c o n t a i n i n g r e g i o n of t h e Tluorina-

t i o n v e s s e l reached temperatures of 6 0 & 7 2 5 " ~ , t h e upper vapor r e g i o n remained

a t lower temperatures.

The maximum temperature recorded on a thermocouple

a t t a c h e d t o t h e e x t e r i o r w a l l of t h e J l u o r i n a t o r 1 2 i n . down from t h e s l i p - o n f l a n g e w a s 500°C.

The average temperature i n t h i s same r e g i o n was about 400°C.

A f t e r completion of f l u o r i n a t i o n , t h e waste s a l t l e f t i n t h e Yluorin a t o r w a s p r e s s u r e t r a n s i ' e r r e d through a f r e e z e valve i n t o a waste c o n t a i n e r ;

and t h e gas from t h e f l u o r i n a t o r w a s passed through an I n c o n e l t r a p , c o n t a i n i n g e i t h e r n i c k e l mesh o r NaF p e l l e t s , which w a s maintained a t approx 400°C.

Prior

t o Run C-9, t h e t r a p contained n i c k e l mesh f o r t h e purpose of c o l l e c t i n g ZrF "snow,

I'

4'

and t h e r e a f t e r t h e u n i t contained NaF p e l l e t s to t r a p e n t r a i n e d s a l t ,

chromium, and zirconium f l u o r i d e s .

During and a f t e r Run C-9,

the t r a p was

termed a "CRP" or complexible r a d i o a c t i v e products t r a p .

'F. W. Miles and W. H. C a r r , Engineering E v a l u a t i o n of V o l a t i l i t y P i l o t P l a n t Equipment, CF-60-7-65, S e c t i o n 15, p. 228.


-

-

12

Downstream from t h e Snow-CRP t r a p , t h e product stream w a s d i v e r t e d through a b s o r b e r s c o n t a i n i n g NaF a t 6 5 - 1 5 0 " ~ t o absorb t h e UF

6'

The un-

absorbed gas, mostly f l u o r i n e , w a s r o u t e d through a chemical t r a p (a NaF bed

a t ambient temperature) t o r e t a i n any r e s i d u a l UF

6 and

subsequently through

a KOH gas d i s p o s a l u n i t t o n e u t r a l i z e t h e f l u o r i n e b e f o r e being exhausted t o t h e atmosphere.

The product, UF6,

w a s desorbed from t h e a b s o r b e r bed by

h e a t i n g it t o approx 400째C i n a f l u o r i n e atmosphere and t h e n passed through two cold t r a p s maintained a t -40째C and

-55째C where t h e uF6 condensed.

The

c o l d t r a p s were i s o l a t e d from t h e r e s t of t h e f l u o r i n a t i o n system and heated

t o approx 80째C t o l i q u a t e t h e UF

C.

Reaction t o Environment

6 which

d r a i n e d i n t o a h e a t e d product c y l i n d e r .

U l t r a s o n i c - t h i c k n e s s measurements of t h e f l u o r i n a t o r were made w i t h an "Audigage," a n u l t r a s o n i c - t h i c k n e s s measurement device, a f t e r t h e Unit O p e r a t i o n ' s p r e l i m i n a r y f l u o r i n a t i o n equipment s t u d i e s .

No detectable m e t a l

l o s s e s could be found i n e i t h e r t h e s h e l l of t h e v e s s e l o r i n t h e bottom head; t h i s could be expected because no f l u o r i n e , uranium-bearing s a l t s , o r UF6 w a s p r e s e n t d u r i n g t h e s h o r t p e r i o d of o p e r a t i o n a t e l e v a t e d temperature and whate v e r a t t a c k occurred w a s so s l i g h t as t o be undetected by t h e measuring equipment. 1.

Chemistry

During VPP Run C-6, a s t u d y w a s made o f t h e i n t e r i o r d e p o s i t s

which formed on the w a l l of t h e f l u o r i n a t o r .

Figure

subsequent chemical a n a l y s e s of t h e s e d e p o s i t s .

4

shows t h e l o c a t i o n and

These d a t a i n d i c a t e a tendency

f o r chromium, presumably from impure f e e d s a l t s , and uranium t o c o l l e c t i n t h e middle vapor r e g i o n o f t h e v e s s e l .

The v a l u e s shown f o r n i c k e l i n d i c a t e t h a t

e x t e n s i v e c o r r o s i v e a t t a c k had occurred i n t h e system during o p e r a t i o n s . A f t e r completion of t h e "M"

and "C"

r u n s d e s c r i b e d i n Table I,

t h e Mark I f l u o r i n a t o r w a s t u r n e d over t o Metallurgy f o r c o r r o s i o n e v a l u a t i o n .

Figure 5 shows t h e i n t e r i o r of t h e f l u o r i n a t o r a f t e r r e t i r e m e n t .

Most o f t h e

i n t e r i o r w a l l s o f t h e v e s s e l below t h e molten s a l t l e v e l s w e r e f r e e of s u r f a c e


UNCLASSIFIED O R N L - L R - D W G 49156

ANALYSES OF DEPOSITS FROM VPP MARK-I FLUORINATOR AFTER RUN C-6

SLIP-ON

Sample Location

I/

ii

!

I 35 in.

si

n.

VAPOR- SALT

Region

Component (wt %j(')

Description

U

Underside of lnconel top flange

Top vapor

Pale blue-green

Interior wall-7 in. below slip-on flange

Upper vapor

Bright bluegreen scale

Interior woIi-8/,o in. below slip-on flange

Upper vapor

Dirty yellowgreen scale

Interior w a l l - ' $ B in. below slip-on flange

Middle vapor

Bright yellowgreen scale

Interior waII-25/26in. below slip-on flange

Lower vapor

Dirty yellowbrown scale

Underside of diffuser cone

Vapor- salt interface

Yellow-green scale

Outside of draft tube

Salt

Pale yellowgreen deposit

scala

No

Ni

Zr

2.45 1.59 49.7 2.00

1.28

8.19 3.3

1.66 3.66 2.30

3.36

27.8

1.6 0.98 15.1

4. Analyses

F 40.4

1.23 33.0

14.4 34.2 3.65 37.5

7.2 48.2 0.75 38.0 10.2 43.3

0.51

38.3

0.15 3.50 23.2 45.0 0.87 41.0 0.26

3.50 33.3

16.3 0.08 40.5

(')ORNL Analyses.

Flg.

Cr

of Deposits from N&rk I W P Flumioator After.Rur: C-6.

I

P w I


-

14 -

ln

r-i I

u


-

15

-

d e p o s i t s b u t t h e r e g i o n s above t h e i n t e r f a c e s were covered w i t h heavy s c a l e A s o l i d r i n g of material, about 1 in. i n c r o s s sec-

and c o r r o s i o n p r o d u c t s .

t i o n , w a s p r e s e n t on t h e i n t e r i o r of t h e vessels w a l l a t about t h e same e l e v a t i o n a s t h e e x t e r i o r rurnace s e a l .

This was a f e w inches above t h e

average e l e v a t i o n of t h e v a p o r - s a l t i n t e r f a c e s .

Samples of some of t h e s e

i n t e r i o r d e p o s i t s w e r e submitted f o r chemical a n a l y s e s &nd i d e n t i f i c a t i o n by x-ray d i f f r a c t i o n .

The r e s u l t s are shown i n Table 11.

Table T I . The Oak Ridge N a t i o n a l Laboratory Analyses of S c a l e from t h e V o l a t i l i t y P i l o t P l a n t Mark I F l u o r i n a t o r a f t e r Run C-15a Component, w t O r i g i n of Sample

U

PTa

N i

Cr

% Zr

F

Approx Composition I n d i c a t e d by X-ray Diffraction I n t e n s i t i e s

Underside o f I n c o n e l slip-on flange

1.95 0.78 45.54 0.79 0.72 39.60

From A Nickel F2 i n l e t tube, approx 2 1 i n . below slip-on flange

0.98 5.10 33.76 0.09 0.64 41.15

From A Nickel F2 0.13 6.64 i n l e t tube, a t vapor-salt interface

90% NiF,10% NaF N i p 2 - 2ZrF4

-

60% NiF2

-

-

30% TsF NiF2 2ZrF4 10% p2*2NaF.ZrF4

8.36 0.02 1.18 43.30

-

a

C. L. Whitmarsh, A S e r i e s of Seven Flowsheet S t u d i e s w i t h Nonradive S a l t , V o l a t i l i t y P i l o t P l a n t Runs, C-9 Through C-15, p. 14, CF-58-5-113 (May 12, 1958).

Most o f t h e s a l t d e p o s i t s were removed by washing t h e i n t e r i o r

0.7 M

H 0 1.8 M KOH, and 0.4 _M Na2C4FI4O6 2 27 room temperature, a i d e d by hand chipping. A f t e r cleaning, a n o t h e r v i s u a l

of t h e v e s s e l w i t h a mixture of

i n s p e c t i o n w a s made and t h e r e s u l t s are given as follows:

at


- 16 Results

Region Vapor

Smooth, e t c h e d appearance n e a r t h e t o p of t h e v e s s e l w i t h i s o l a t e d , shallow p i t s . A yellow-to-green d e p o s i t e n c i r c l e d t h e v e s s e l from a p o i n t approx 10 i n . down to a p o i n t approx 20 i n . from t h e t o p . S e v e r a l small areas of f l a k i n g and s c a l i n g were noted a t approx 16 i n . from t h e t o p i n t h e d e p o s i t zone. The area from 20 i n . down t o approx 24 i n . from t h e t o p had a b l u i s h c a s t and w a s rougher i n t e x t u r e t h a n t h e t o p s e c t i o n .

Vapor-salt interface

Smooth m e t a l l i c appearance w i t h d i s t i n c t i n d e n t a t i o n s e n c i r c l i n g the vessel a t several levels.

Salt

Smooth m e t a l l i c appearance. c o r r o de d

.

F l a n g e - t o - v e s s e l weld n o t n o t i c e a b l y

I n t h e middle vapor region, a t i g h t l y adherent, yellow-to-green d e p o s i t remained on t h e w a l l of t h e f l u o r i n a t o r .

Samples of t h i s d e p o s i t , s u r f a c e , and

subsurface m i l l i n g s , were removed and submitted f o r chemical a n a l y s e s .

Figure

6

d e t a i l s t h e r e s u l t s which i n d i c a t e t h a t chromium which had p r e v i o u s l y been round t o c o l l e c t i n t h e upper vapor r e g i o n of t h e f l u o r i n a t o r had p e n e t r a t e d i n t o t h e v e s s e l w a l l to some depth g r e a t e r t h a n 10 m i l s .

This chromium con-

c e n t r a t i o n g r a d i e n t w a s found b o t h i n t h e upper and middle vapor r e g i o n s a l -

though h i g h e r c o n c e n t r a t i o n s were found i n t h e former r e g i o n .

No e x c e s s i v e

q u a n t i t i e s of s u l f u r over t h a t p r e s e n t i n t h e base material were found. 2.

Dimensional Analysis Micrometer measurements w e r e t a k e n i n t h e t h r e e major r e g i o n s of

t h e f l u o r i n a t o r i n a l l quadrants and show t h e g r e a t e s t w a l l - t h i c k n e s s l o s s e s t o be c o n c e n t r a t e d i n t h e vapor r e g i o n of t h e v e s s e l s h e l l .

Figure

7 shows

a schematic drawing of t h e v e s s e l and denotes t h e s e c t i o n s t h a t were removed

from t h e v e s s e l f o r t h e s e measurements and f o r metallographic study. d a t a are given i n Table 111. the northeast-by-east

The loss

A f u l l - l e n g t h v e s s e l s e c t i o n w a s removed from

quadrant and micrometer measurements t a k e n every v e r t i c a l

inch t o e s t a b l i s h a corrosion wall-thickness-loss p r o f i l e .

Figure 8 shows t h i s

p l o t and p i n p o i n t s t h e maximum metal loss of 47 m i l s as approx 1 2 i n . below t h e bottom of t h e s l i p - o n f l a n g e .

.


- r7 -


- 18 UNCLASSIFIED ORNL-LR-DWG 49158

F U L L LENGTH SECTION REMOVED HERE

-

-AVERAGE OF OR SALT INTERFACES

@

CIRCULAR COUPONS TREPANNEO FROM VESSEL W A L L

Pig. 7. Schematic of Mark I VPP F l u o r i n a t o r Showing Areas Rernoved f o r Netallographic Examination and Micrometer Measurements.


- 19 Table 111.

-._..

-

a

Wall-Thickness Tosses on Couldoiis Perfloved f r o m t h e Mark I V o l a t i l j t y P i l o i 321 a n t JJ N i c k z l Flimri n a t o r b

_I___

Loc a t i o n __ E Ievat i.on Sample (Tnches be low Number sli-p-on flange) Quadra.r.t

Wa 1. 1- ‘i’hnj~ ckne s s

Loss

Region

(mils)

N- 1

12

Nortii

Vapor

38

E-l

l?

East

Vapor

29

13

South

12

We sL’

Vapor

33 7

33 35 35 35

North

S-1

w--1 N- 2 E-2

S-2

w-2

45 l+5

3 E-3 N-

s- j w-3

45 45

Vapor

Vapor-salt i n t e r r a c e

!dan t

Vapor-s a l t i n t e r f a c e

6 !+

South

Vapor-salt i n t e r f a c e

8

West

Vapor-salt i r i i e r f a c e

10

East

Salt

Salt

10

South

Salt

West

Salt

I1-

North

.-

By rnicrotiieter mea surcment .

a

bOriginal w a l l thickness

250 m i l s .

8

.._I-.-

15 I


-

20

-

UNCLASSIFIEU ORNL-LR-DWG 40728

SLIP-0 I FLANGE

-4

0

I

5 $0

45

-.e

I

w CY

20

z

4 LL

z

25 30

P

9

m 3

i

H5 1 J

w I m

0

E z 5

35 40

Y 2

45

50 55

DOITOM

Fig. 8. Corrosion P r o f i l e and Typical. Microstructures from the Mark T VPP Yliiorinator. ( P r o f i l e based on microme1,er measurements from n o r t h e a s t quadrant full-length s h e l l s e c t i o n . )


3.

21 -

Metallographi c Study Bzsed on -the c o r r o s i o n wall-ihi.ckne3s-loss p r o f i l e p l o t , 8 r e a s

were s e l e c t e d frorii t h e f u l l - l . e n g t h s e c t i o n of the f l u o r i n a l , o r and from p r e v i o u s l y trepanned samples for metalJ-ographic study.

a r e a s i s shown i n F i g . 8.

The l o c a t i o n o f these

I n the a s - p o l i s h e d c o n d i t i o n , some s l i g h t roughening

of t h e s i u f a c c s of t h e samples Lias noted.

No grai.n-boundary rnodificatlons

s u c h as i s commn t o i n t e r g r a n u l a r c o r r o s i v e a t t a c k

A f t e r e t c h i n g w i t h an 0.5% Xl, approx

could. be found,

60% HC,Ii30,

and approx

HNO mixture, t h e g r a i n boundaries of t h e i n t e r i o r s u r f a c e samples appeared 3 darkened below t h e exposed. s u r f a c e s t o depths v a r y i n g from 4 'LO 25 m i l s .

Fi-gyre

40$

8 iI.l.ustrai;es t h e t y p i c a l struc-Lures found a t v a r y i n g e l e v a t i oris on

t h e i n t e r i - o r s u r f a c e s of t h e f l u o r i n a L o r w a l l - .

Tlie deepest penetra1,i ons were

found on sarruples from -ihe middle vapor r e g i o n of the v e s s e l , t h e v a p o r - s a l t

i n t e r f a c e , and t h e s a l t reg;i.on of t h e f l u o r i n a t o r .

The e x t e r i o r s u r f a c e sam-

ples a l s o showed i n t e r g r a n i i l a r a t t a c k v a r y i n g from 3 t o 8 m i l s i n d.epth.

Widely v a r i a n t grai.n s i z e s were found i n t h e m e t a l l o g r a p h i c s a m -

p l e s examined.

A siimrnary o f these s i z e s , converted t o averaze ASTM g r a i n - s i z e

nuuibers, i.s shown i n T a b l e I V .

Sullimary of Grain S i e s i n Samples Removed from t h e Mark 1 V o l a t i l i t y Pilot P l s t i t F l u o r i n a t o r a

IT3b'Le TV.

Distancr

down f r o m

slip-on i l a n g e (in. )

-_-.

1

3

13- I./?

70

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~ 91/2 35 43

Re@ on

.____

Vapor Val~oe Vapor Vapor Vapor Vapor Vapor- s a l t i n t e r f a c e Sali

AS V4

Grain s i e n i m b e r

5-6

2-3 >1

1 2

5 5

F G

a Grain s i z e s from i n t e r i o r w a l l and e x t e r ? o r w a l l sampI_es were approxi mately e qisal

.


- 22 A t a l a t e r da.te, rln an attenip-t t o determine the reasons Tor t h e v a r i a n t g r a i n s i z e , d i f f r a c t o m e t e r t r a c e s were o b t a i n e d on sel.ected. samples removed from the w a l l of t h e Mark I f l u o r i n a t o r , .

Samples were taken from

t h e I-, 12-1/2-,and 43-5.n. l e v e l s , respecti-vely, below t h e bottom o f i h e vessel slip-on flange.

The maximum amount of r e s i d i i a l s t r a i - n w a s noted f o r

t h e 1 - i n . sample w i t h l i t t l . e ,

i€ any, evidence of r e c r y s t a l l . i z a t i . o n having

t a k e n p l a c e d u r i n g t h e Mark I o p e r a t t o n s .

A very l i m i t e d . amount of r e c r y s t a l -

l i z a t i o n appeared t o have occurred i n t h e l2-1/2--in.

sample s i n c e t h e r e seemed

o n l y sli.ght.1.y 1.~3:;~ s t r a i n presenl, i n t h i . s sample when compared. t o t h e one above.

Tie 11-3-i.n.-sample t r a c e s showed c o n s i d e r a b l y I.ess r e s i d u a l s t r a i n

p r e s e n t t h a n e i t h e r of t h e o t h e r sauples.

The i n d i c a t i o n s were t h a t p a r t i a l . ,

i f n o t compl.et,e, r e c r y s t a l l i z a t i o n had taken p l a c e i n t h e lower p o r t l o n of

t h e f l u o r i n a t o r wall. Figure

9

shows a s e c t i o n through t h e g i r t h weld which was

l o c a t e d i n t h e s a l t phase of t h e f l u o r ? - n a t o r . A f t e r e t c h i n g , t h e specT-men showed no c o r r o s i v e a t t a c k a t ].ow magnificatj-on.

A t hj-g’ner magnifi-cation,

t h e ilreld d e p o s i t showed a. grain-boundary a t t a c k similar t o t h a t found i n t h e

base metal., b u t t o a l e s s e r degree of s e v e r i t y .

E a r l y work on L n i c k e l corros-ion rods p l a c e d i n t h e Mark I

f l u o r i n a t o r i n d i c a t e d s u l f u r contamination was probably a f a c t o ? i n t h e cor-

rosive a t t a c k of t h e .vessel.

8 I n view of

t h e l a c k of evidence frorn chemical.

analyses, o t h e r aLternpts were made t o prove t h e presence of suli”ur a t -the grai-n boundaries of i n t e r i o r w a l l specimens from t h e Mark I f l u o r i . n a t o r .

The use of s u l f u r p r i n t papers d i d not provi.de p o s i t i v e evidence

of t h e e x i s t e n c e of sulfur compounds a t t h e mating s u r f a c e s of t h e g r a i n s .

One sample from t h e middle vapor r e g i o n of t h e f l u o r i n a t o r d i d prese1i-L -tile c o l o r s d e s c r i b e d as needed. for t h e i d e n t i f i c a t i o i i of n i c k e l s i i l P i d e .

F i g u r e 10 shows t h e grain-boundary d e p o s i t a t t h e 1 2 - i n . l e v e l below t h e bottom of t h e s l i p - o n f l a n g e a f t e r etch5 ng w i t h cyaiiri d e - p e r s u l f a t e and. p a r t i - a 1

repolishing .Lo show t h e d e p o s i t t o i t s best, advantage.

However, d u p l i c a t e

res11.I-ts could n o t be o b t a i n e d w i t h t h e method. a u L. R. T r o t t e r and E . E. Hoffman, P~ogressReport on V o l a t i l i t y P i l o t P l a n t Corrosion Problems t o April 21, 1-95I, OHNL-2&95 (September 30, 7 958).


-

23

-

I

Exterior

Interior ( c o n t a c t with s a l t phase

(contact with

air)

I

F i g . 9. Macrostructure of S e c t i o n Through G i r t h Weld 47 i n . Below Top Flange of Mark I VPP F l u o r i n a t o r . Etchant: Acetic, n i t r i c , h y d r o c h l o r i c a c i d . 10 X.


-

24

-

0)

W

I

V

z-

f

-

I

002

00: -

9

X

0

0

0

.oo

F i g . 10. Photomicrograph of Sample T r o m I n t e r i o r Surface of Mark I VPP L Nickel F l u o r i n a t o r 12 i n . Below S l i p - o n Flange (Vapor Phase) Showing Grain Boundary Deposit. Deposit w a s p a l e yellow under nonpolarized i l l u m i n a t i o n and b l a c k under p o l a r i - e d l i g h t i n accordance u i t h H a l l ' s method ? o r i d e n t i i y i n g n i c k e l sulf'ide d e p o s i t s . Etchant: Potassium cyanide-ammonium p e r s u l T a t e , p a r t i a l l y r e p o l i s h e d . IOOOX. Reference: A . M. H a l l , " S u l f i d e s i n Nickel and Nickel A l l o g s , " Trans. Met. SOC. AIME 152, 2&3, 1943.


- 25

-

S u l f u r i n almost any chemical form i n c o n t a c t w i t h n i c k e l a t h i g h temperatures w i l l r e s u l t i n t h e formation of a low-melting n i c k e l - n i c k e l s u l f i d e e u t e c t i c p r i m a r i l y along g r a i n boundaries, l e a d i n g t o embrittlement

of t h e material.9 bend t e s t e d .

Consequently, samples of t h e f l u o r i n a t i o n v e s s e l w a l l w e r e

'The samples d i d n o t show b r i t t l e behavior.

Two o t h e r t e c h n i q u e s were c o n s i d e r e d as i d e n t i f i c a t i o n methods f o r t h e grain-boundary d e p o s i t s d e s c r i b e d .

One w a s t h e use of a m i c r o c h i s e l ,

p r e s e n t l y under development by t h e Metallography Group of t h e Metallurgy Division, by which some of t h e grain-boundary d e p o s i t could be removed and subsequently submitted f o r x-ray d i f f r a c t i o n a n a l y s i s .

The v e r y s m a l l s i z e

of t h e grain-boundary d e p o s i t s prevented t h e m i c r o c h i s e l ' s usage i n t h i s

situation.

The second technique c o n s i d e r e d w a s t h e u s e of an e l e c t r o n probe

microanalyzer which could p o s s i b l y i d e n t i f y a s m a l l p o r t i o n of t h e d e p o s i t by

--

x-ray d i f f r a c t i o n analysis, i n s i t u .

Such an i n s t r u m e n t i s n o t y e t a v a i l a b l e

at ORNL and it w a s n o t p o s s i b l e t o o b t a i n s e r v i c e time on t h e f e w i n s t r u m e n t s c u r r e n t l y i n o p e r a t i o n i n t h i s country.

Consequently, t h e n a t u r e of t h e Mark I

f l u o r i n a t o r grain-boundary d e p o s i t s w a s l e f t i n doubt.

4.

Summary of Corrosive A t t a c k Table V summarizes t h e maximum c o r r o s i o n l o s s e s of all t y p e s

found i n t h e t h r e e major r e g i o n s of t h e VPP Mark I f l u o r i n a t o r . a t t a c k w a s c a l c u l a t e d t o be s a l t s d u r i n g t h e VPP "M"

46

runs

The maximum

mils/month based on exposure time t o molten

(1-48) and "C" runs (1-15) or 1 . 2 m i l s / h r based

on f l u o r i n e sparge t i m e d u r i n g f l u o r i n a t i o n of molten salts.

The maximum

a t t a c k o c c u r r e d i n t h e middle vapor r e g i o n .

D.

D i s c u s s i o n of R e s u l t s 1.

I n d i v i d u a l Actions of F

&Q

and Fused F l u o r i d e S a l t s

Major c o r r o s i v e a g e n t s i n c o n t a c t w i t h t h e VPP L n i c k e l f l u o r i n a t i o n v e s s e l , Mark I, were e l e m e n t a l f l u o r i n e , uranium h e x a f l u o r i d e , and

'W. A. Mudge, "Nickel and Nickel-Copper, Nickel-Manganese, and R e l a t e d High-Nickel A l l o y s , " The Corrosion Handbook, (ed. by H. H. W i g ) , p. 679, John Wiley and Sons, Inc., New York, 1948.


Table V.

Summary of Maximum Corrosive Attack i n Each Major Region and Quadrant of t h e Mark I V o l a t i l i t y P i l o t P l a n t L Nickel F l u o r i n a t o r

Location Elevation (inches below slip-on flange )

Quadrant

Region

North

Vapor

East

Vapor

South

Vapor

12

West

Vapor

35

North

35

East

35

South

35

West

45 45 45 45

North

Salt

East

Salt

South

Salt

12

12

West

Vapor- s a l t interface Vapor-salt interface Vapor- s a l t interface Vapor- s a l t interface

salt

Intergranular Wall Penetration thickness I n t e r i o r Exterior lossa wall wall (mils) (mils) (mils)

38 29 33 47

Attack (mils)

T o t a l Rate Lossesb

mils/

mils/hr (Molten (F2 sparge s a l t time)c time)d month

21

3 4 3 5

65 53 59 73

33 37 46

6

18

7

31.

20

0.5

4

17

6

27

17

0.4

8

23

5

36

23

0.6

10

17

8

35

22

0.6

10

25

3

38

25

33 40 42

0.6

11

4 4 5

24 25

0.7 0.7

8

15

24

Tot a1 Corrosive

20

23

21

22

41

21

26

%y micrometer measurement,

b C

Includes e x t e r i o r i n t e r g r a n u l a r p e n e t r a t i o n .

(1-48) runs

Based on molten s a l t residence t i m e during VPP "M"

and "C"

s a s e d on f l u o r i n e sparge time during f l u o r i n a t i o n of molten s a l t s .

8

4

(1-15) m n s .

1.1

0.9

1.0

1.2

0.5

I

Iu o\ I


- 27

-

molten f l u o r i d e salts, genera1l.y of t h e NaF-ZrP -UF

4

4 type.

'The c o u i p a t i b i l i t y

of each of t h e s e agents i n c o n t a c t wi.th metals has r e c e i v e d increased. a-titen-

t i o n duying t h e past, decade, b u t a composite system has riot been s t u d i e d e x t e n si.ve1y

.

F l u o r i n e , a most a c t i v e elerrlent, was known -Lo r e a c t w i t h v i r - t u a l -

ly every metal under su~itab1.e c o n d i t i o n s . fe1.t t o be i m p a r - L e d . by p a s s i v e f l u o r i d e

Resistance t o f u r t h e r a t t a c k was

rilrns

which form on m a t e r i a l s .

10,11,12

For nickel, t h e only known b i n a r y conipou.nd w i t h f l u o r i n e w a s found t o be nickelous f l u o r i d e , NTF2 (ref 13) The melting p o i n t of Ni.F

2

e

had been r e p o r t e d

t o be about lGOG째C, -dell i n excess of t h e operati-ng tempera;tures 114

The vapor p r e s s u r e of NiF2' approx 1 x lo-' 650째c, appeared s u f f i c i e n t l y low s o -that li.Ltle v o l a t i l i z a t i o n of

of -the f l u o r i n a t o r

I

t i v e f i l m would occiir.

15

(600-725~~) null

Kg at

tlx p r o t e c -

Kecen-t; experiments at t h e Argoi-me National Laboratory had i n -

d i c a t e d .that t h e r e l a t i v e amounts oE f l u o r i n e consumed by

8

n l c k e l v e s s e l and

the change i n r a t e - l a w behavi-or w i t h temperature can be represented. as shown i n F i g . 11. A t lower temperatures,

300 t o 4OO0C, a l o g a r i t h m i c rate l a w ap-

peared t o hold, b u t a t hi.gher teuiperatures, 500 t o

6oo0c,

a p a r a b o l i c behavior

seened p r e v a l e n t .

10

__.

M. J. S t e i n d l e r and R. C. Vogel, Corrosion of Materials i n the Presence of F l u o r i n e a t E l e v a t e d Ternpcratitres, Argonne National Labora3,ory Report, ANT,- 5x62 ( January, 1957 )

.

11.

1 _ -

C . S l e s s e r and S. R. Schram, Pi-eparati.on, P r o p e r t i e s , arid Technology of F l u o r i n e and Organic Fluoro Compounx, Natioiial Nuclear Energy S e r i e s , Div. VIL, Vol. 1, pp. 173, McGraw-Hill, New York, 1951.

"E.

I .

15'7,-

J. Bm-ber and. 11. A. Rernhardt, K-1421 ( A p r i l 9, 1 . 9 5 9 ) ( c l a s s l f i e d ) .

- 7,

13:1. J . Emel-eus, F l i m r i n e Chemistry ( e a . by J. iI. Simons), 1, Acaderriic Press, Tnc. , New York, 1950. 11 .L

Lau.rer,ce L. Qpill ( e a . ), Chemistry and Metallurgy of M i s c e l l a m o u s Materials: Thermodynamics, National- Nuclear E n e r g y S e r i e s , Div. I V Y Vol. I9b, p. 207, McGraw-Hill, New York, 1950.

l 5 M . Faber, R. T. Meyer, and J. L. Margrave, "'lhe Vapor P r e s s u r e of Nickel F l u o r i d e , " 3. Phys. Chem. -62, 883 (1914-8). 1 1 1 -

_ I


- 28 UNCLASSI FlED 55786

ORNL-LR-DWG

20 18 16

14 12

10

8 6

4 2

0

0

1000

2000

3000

TIME ( m i n )

Pig. 11. Consiirrptioii of Fluoriiie by a Nickel Vessel, R e f e r e n w : R. K. Steunenberg, T,. Seiden, and fi. E . Griffin, "The Reaction of P'luorine wi-tli N i c k e l Surfaces, Argome National..L a b o r z i o q Chemical Engifieering Division Summa-ry Report, July, August,, September, 1958, NL-59?41 pp 42-43. ~

.


- 33

-

More d e t a i l k d work i n t h i s f i . e l d has been r e p o r t e d by ORGDP.

16

Nickel w a s fou.nd t o form a continuous, ad.herent fl-imride f i 1 . m w-ith a-n und i l u t e d f l u o r i n e atmosphere a t temperatiires up t P about

980째C. Rl.ectron

microscopy i n d i c a t e d t h a t t h e n i c k e l f l u o r i d e f i l m s had few f l a w s i n t h e i n di-vidual c r y s t a l s which would p e r m i i d i r e c t access o f t h e flii.oride t o t h e

n i c k e l s u r f a c e ,underneath.

The s t i i d l e s a l s o i n d i c a t e d t h a t , as t h e n i c k e l

f l u o r i d e f i l m thickened, more r e s i s t z n c e t o a t t a c k w a s obtained.

However,

oraconsi-derable i n t e r g r a n u l a r a t t a c k of the m e t a l l i c n i c k e l w a s noted a t -tenii:~.-

815 and 980째C ( F i g . 12). Tne d.epth of i n t e r g r a n i i l a r p e n e t r a t i o n w a s esti.mated t o be 5 t o 8 t i m e s t h e average a t t a c k as c a l c u l a t e d from t u r e r of approx

s c a l e formation.

The r e p o r t i n d i c a t e d t h a t -tile primary mechanism of a t t a c k

appeared i o be d i f f u s i o n al.ong t h e c r y s t a l boundaries.

?lk second major c o r r o s i v e a g e n t p l a c e d i n c o n t a c t with tile

Mark I f l u o r i n a t i o n v e s s e l d u r i n g operations w a s UP,-. 0

The e f f e c t of this

compound. o n rile-tal5 had. undergone i n v e s t i g a t i - o n i n connection with t h e rksi.gn,

c o n s t m c t i . o n , and o p e r a t i o n of t h e ORGDP."'

Sone r e c e n t work a.t t h e same s i t e

i n d i c a t e d t k i a 1 ; on A n i c k e l samples which were coated wi.t;li nickel. f l . u o r i d e f i I.ms

of 37 000 a n d

714-000

A, t h e average p e n e t r a t i o n o f t h e n i c k e l by UF

6

a t about

815"C, c a l c u l a t e d from the average n i c k e l f l u o r i d e scale formation, appea.rt:d

t o be about one t h i r d oi" LhaL experiericed w i - L h Yluorine a t about 700째C. ( r e f 1.6)

L a t e r work by t h e same group i n d i c a t e d tha-'i a t times one o r d e r of rc1agnitu.d-e

grea-ter (hundrecls of h o u . ~ sversu.s t e n s of hours) NiP

2

i s l o s t by v a p o r i z a t i o n

and/or a r e a c t i o n p r o c e s s s o t h a t c a t a s t r o p h i c a t t a c k can occur by additional. UF/ c o n t a c t . C)

18

The n i c k e l exposed 'io t h e I F 6 a t those e l e v a t e d temperatures ex-

hlibl-ted a grain-boundary a t t a c k beneath t h e f l u o r i d e s c a l e q u i t e siml.lar t o I__..

l6C. F. Kale, E . J. Barber, SI. A. Rernhardt, and Karl E. Rapp, High Temperature Corrosion Study, I n t e r i m Report for t h e Peri-od. November, 1958, Through May, 1959, K - L - ~ Y (~J u l y 28, 1959). -I___

Ir'J. J. K a t z and E. Rabinowitch, The Chemistry oP Uranium N a t i o n a l Nuclear En-ergy S e r i e s , Div. V I I I , Vol. 5, pp. j-L1~15--!t6>McGraw-Hill, New York, 1951. 18E. J. Earber, Technical Division, ORGDP, Jan. 7, 1960, P r i - v a t e communi c a t i o n


-

30

-

F i g . E. M i c r o s t r u c t u r e s of A Nickel Coupons ( a ) A s Received; (b) A f t e r Exposure to F2 at 81'j"C: for 4 hr and f o r 32 hr a t Lower Temperatures; ( c ) A f t e r Exposure t o F2 at 980째C f o r 35 hr a n d f o r 350 hr a t Lower Temperatures. Etchant: Soldium cyanide, ammonium p e r s u l f a t e . IOOX. Reference: C. F. H a l e , E. J. Barber, R. A. Bernhardt, and K a r l . E . Rapp, High Temperature Corrosion Study, .Interim Repol-t f o r the Period, November, 1958, Tarough May, 1359, ~ ~ - 1 1 9 8 -(July 28, 1959).


.-

31- It wah a l s o obsemwd that

that, experienced i n t h e exposures t o f l i i o r i n f .

both ni c k c l f l u o r i d e and UF

G

c o r r o s l o n p r o d u c t s ha4 a p p r e c i a b l e vapor p r e s -

surf's ai, Lhose L e s t ieniperaL1ires aod w e r e observed t o migrate i o t h e c o o l e r

portions or Lhe r e a c t o r by vapor-phase i r a n s f c r ,

Tn a d d i t i o n t o F a n d IJY 2 6' f u s e d - f l u o r i d e s a l t s were a l s o ia c o n t a c t ?/it11the Mark I VPP â&#x201A;Ź l i i o r i n a t o r . A t ORPSL, ronsiderabbe p r o , ~ ~ e s has s

been mati? i n determining ma ttJrial corflpaiibi Ii t y i n v a r i o u s f u s e d - f l u o r i d e -

s a l t systems throuzh the z \ i r c r a f L Rearto r Experiment aqd Molten-Sali R e a c t o r

I'l*c,j:icLs.I$'

Nickel -base a l l o y h were found iu be,

i n g e n e s s i ; s u p e r i o r i o other

commercial a1 1 nys ror t h e containnieot of' â&#x201A;Ź l u o r i d e s a l t mixtures under dynamic

1'10 J condi t,i ons 2.

.

C o l l e c t i v e Attack iXl-riaS :FR.uoriuati.on _I___..... _____

I...~.

The f 1iior-in.ati-on cycle of t h e i"luoi?ide v o l a t i l i - t y p r o c e s s pro-

tliiced E r e a t E r cor:rosive a t - t a c k by t h e coll.ective system of F,, I'iiioTid? s a l t s on ili

...

UF6,

aiid f u s e d

ckcl than had^ been r e p o r t e d f o r h e indivi.dual c o n s t i t u e n t s .

D i r i n g WP o p e r a t l o n s , t h e Mark I L-nickel f l . u o r i n a t o r d i s p l a y e d Inaic-imum

rosion r a i e I-osses o f 1.2 miI.s/hr,

based on E'

2

b m e d on m o l t e n - s a l t r e s i d e n c e t i m e dur-lng VPP

(1--15).

sparge -i;irne, o r

"M" runs

COT-

46 mils/month,

(1-J-La) and

"C" r u n s

These r a t e s i n c l u d e wal~lt h i c k n e s s o r meial l o s s e s as detemnlned by

dimenslonal. analysis p l u s i n t e r g r a i l u l a r p e n e t r a t i - o n as d.eterniinF:d by metallo-

graphic examination.

The rates a r e g e n e r a l l y c o n s i s t e n t w i t l i e a r l y bench-scale

work on t h e v o l a t , i I . i t y procesc.

20

For convenience i.n r e p o r t i n g , the proposed reasons for t h e high

c o r r o s i v e a.-tkack on t h e E!-ii.orina.tion

headings:

v r s s e l w i l l be d i s c n s s e d under four major

(a) I n t e r i o r Bulk Losses, ( b ) I n - t e r i a r T n t e r g r a i u i a r ,flt.tack,

( c ) Exterior I n t e r g r a n u l a r Aktack, and

(a)

Grain-Size V a r i a t l o n s

.

" C o n s i m c t i o n MateriaJ-s for Molten-Sal t, Reactors, I ' "14. D. Manly et al. N - u i d Fuel R c a c t o j r c zd. by Lane, MacPherson, and Maslan) Chap. 13, Addisoni%sley,


a.

32

-

I n t e r i o r Bulk Losses The f i r s t p o r t i o n of t h i s s e c t i o n d e s c r i b e d "conditioning"

treatmen-ts whereby n i c k e l f l u o r i d e vas induced on t h e wa!.ls f l u o r i n a t o r p r i o r t o ac-Lual hish- teniperai;ii.i'e o p e r a t i o n s .

oi' t h e Mark I

This v-as i n iiarmo:t~y-

w i t h p r e v a i l i n g generalizat5.ons concerning p a s s i v e f luoi-ide f i l m s , which, when

formed on exyosed rnietnl s u r f a c e s may i n h i b i t Yur-Lher at-Lack by elemental fluorine.

However, based. upon ORGDP and.Arg:on.ne National L&ora-toi*y work, l 6 , 2 l

it appears t h a t p a s s l v a t t o n temperature should. have been equal t o , o r g r e a t e r than., the o p e r a t i n g temperature, r a t h e r than m-150째 C y i n o r d e r t o induce g r e a t e r Y i h thicknesses.

The work b y Iiale et, -a] .. 09

i n d i c a t e d t h a t while cor-

r o s i v e attack on n i c k e l by f l u o r i n e d5.d n o t cease a f t e r t h e n f c k e l f l u o r i d e

f i l m thickened, a d d i t i o n a l r e s i s t a n c e t o a t t a c k m.s obtained at, t e s t temprra-

t u r e s up t o 9 8 0 " ~ . Considering t h e very high ra-Le losses round

removed Trorn t h e wall of t h e f i r s t WP f l u o r i n a t o r ,

011

sainpl.ec

i.t would appear t h a t

c o n d i t i o n s were present; i n t h e v e s s e l vhicii (1) d i d n o t al.low s u f f i c i e n t f i l m

thickeni-ng t o occur,

( 2 ) reduced t h e p r o t e c t i v i t y o r thickened. n i c k e l fluorri.de

films, or (3) p e r m i t t e d c a t a s t r o p h i c l o s s e s of t h e n i c k e l f l u o r i d e f i l m s .

Free f l u o r i n e w a s present, p e r i . o d i c a l l y , during a l l of tile

Vl?P o p e r a t l o n s i n q u a n t i - t i e s above those arnoi.ints necessary t o o x i d i z e any UF

4 in

t h e f l u o r i d e s a l t mixtures t o I F 6 .

Tnus, even though c a t a s t r o p h i c

l o s s e s of o l d n i c k e l f l u o r i d e films might occur, n e w f i l m s would. have opport u n i t y t o form,

Therefore, a continimiis cycle of i . n i t i a l l o s s , reformati-on,

and secondary l o s s of the n i c k e l f l u o r i d e f i l m s forming on t h e walls of t h e

f l u o r i n a t o r i s proposed as t h e method whereby the large losses of bulk metal

occurred.. This proposed l o s s cycle could be i n i t i a t e d and maintained i n s e v e r a l ways depend.ing on t'le region of t h e f l u o r i n a t i o n v e s s e l under consideration.

2h.

I n t h e s a l t region, fused~f l u o r i d e sal:; b a t h s could d i s s o l v e Lhe

K. Steunenber& L. Seiden, and H. E, G r i f f i h , "The Reaction o f F l u o r i n e w l i t h Nickel Su.rTaces, " Argonne National 1,ahoratory Chemri.cal Engineering Dlivision, Sunlriiary Xeport, July, August, Septem'mr, 1958, ANL-5924, pp. 11.2-43.


- 33 n i c k e l f l u o r i d e films u n t i l s a t u r a t i o n ot t h e b a t h s w i t h n i c k e l fluo-ride

It has been r e p o r t e d t h a t Nj.F2 i s s o l u b l e i n equimolar NaF-ZrF 4 ( r e f 22) t o t h e e x t e n t of 1.8 wt % at 7OO"C.

occurred.

A t t h e v a p o r - s a l t i n t e r f a c e , similar d i s s o l u t i o n could have

occurred t o remove p r o t e c t i v e w a l l f i l m s .

A l s o , a washing a c t l o n caused by t h e

fl-uorine sparge a g i t a t i o n and t h e rise and f a l l of t h e b a t h l e v e l could ai.d

f i l m removal.. I n t h e vapor region, w-liere maxj.mum metal l o s s e s occurred, n i c k e l f l u o r i d e f i l m s that have l i m i t e d p l a o - t i c i l y a t t h e lower o p e r a t i n g Lecnperatures rnri.ght be lost through cracking o r r u p t u r i n g .

Also, t h e d i f -

f e r e n c e i n l i n e a r c o e f P i c i e n t s of' thermal expansioii o f n i c k e l and ni-ckel

f l u o r i d e would be s u f f i cien'c to exaggeraLe the s p a l l i n g -t;end.ency. These

a c t i o n s may also occur i n the o t h e r t w o major r e g i o n s of t h e Yluorination

v e s s e l , b u t t h e o t h e r l o s s mechanisms d e s c r i b e d f o r those a r e a s would proba-

b l y predoml na-l;e,

Cathers has suggested an a d d i t i o n a l mode of fi.lrn l o s s for

t h e vapor r e g i on, i. e.,

di.ssolu.tion of n i c k e l f l u o r i d e i n very h i g h l y c o r r o s i v e

l i . q u i d s whi ch condense i n .the c o o l e r zones of t h e f l u o r i n a t o r .

Fluoride

cornpounds of intertnediate v o l a t i l i t y such as "chose conthining high-valent chromium, s u l f u r , titaniuui, and/or s i l i c o n . , might be r e s p o n s i b l e .

This con-

densate i s p i c t u r e d as belng extremely v a r i a b l e i n composition ( p o s s i b l y

i n c l u d i n g KF arid. water vapor, i.f t h e y were 1mintentionall.y admitted into t h e

system) and i n d i s s o l u t i o n a b i l i t y .

A f b e r t h e condensate forms i n

; i

rela-

t i v e l y c o l d r e g i o n o f -the v e s s e l , i t would ruii down t h e w a l l toward a h i g h e r temperature zorte, where i t could t h e n d i s s o l v e the n i c k e l f l u o r i d e s u r f a c e

films.

P r o g r e s s i n g f u r t h e r down the walls of t h e v e s s e l , it would eventual.ly

r e a c h a temperature zone where it could r e f l u x , and l e a v e w i t h t h e product stream or re-enter. i n t o t h e v e s s e l c o r r o s i o n eiivirorment *

2?

C. L. \\kitmarsh, Uranium Recovery from Sodium-Zirconium F l u o r i d e - S a l t Mfxtures, V o l a t i l i t y P i l o t P l a n t RGns L-1. Through L-9, CF-59-9-2-(September 30, 1959). I

23

G. I. Cathers, ORNL Chem. Tech. Div., Private communication.


Support is given t o t h e C a t h e r s ' sugge:;-t,ion i n view o f

the design u s e d for t h e VPP f l u o r i n a t i o n vessel. and t h e r e s u l t s of t h e cherlii-

c a l s t u d i e s on t h e i n t e r i o r w a i l d.eposi~t,sfrom ,the vapor r c g i o n of tile vessel..

The Marl.; T f l u o r i n a t o r lleati ng system was designed Lo p i ~ ~ d u cceo o l e r tempera-

t u r e s i n the upper r e g i o n s OP t h e vessel.

The maximuin teniperature recorded

on a thermocouple a t t a c h e d t o t h e e x t e r i o r v e s s e l wal.1. 17 i n . below t h e sl-i.p-on f l a n g e was 500째C, while the average temperature i n t h ? same r e g i o n

was l+OO"C.

The thought was t h a t a c o o l e r t o p v e s s e l zone wou3.d pennit,

depositioii of low v o l a t i l i t y compounds thaL m i @ t

entl*ap ut-anium products.

A f t e r some i n d e f i n i t e time oP tleposjti-on, i t w a s f e l t t h a t t h e s e l a y e r s

would. gmd1.ml.l-y f z l l back i n t o t h e sliLt b a t h s and become ava-ilable f o r f u r t h e r f l u o r i n a i, ioil. I n support of t h e condensab1.e corrosi-ve 1jLquid theory, chemical a n a l y s e s o f r e s i d u a l w a l l . d e p o s i t s and m i l l i n g s kern the f I..uorina-i;or vessel w . l l s i n t h e mi.ddle vapor regj.on (Fip. c o n c e n t r a t i o n s o f uranium arid chroiniurn.

4

and^

6)

s'nowed h i g h

Thus, i.t would seem t h a t en-Lrain-

men-t o f uranium and redeposi.tion of materials c o n t a i n i n g uranium d i d occur and -ilia?, chromium vas a p a r t of t h e eatrappiny; &gent, or a g e n t s . Rather t h a n d e s c r i b i n g tb.e agents which seem t o have a l d e d t h c c o r r o s i o n progress i n t h e m i d d l e vapor region as condensah12 l l q u i d s

which dissoJ.ve nickel f l u o r i d e , favor i s given t o -iiie i d e a t h a t t h e n i c k e l f l u o r i ~ d ecomplcxed w i t h o.ther

iiiore

vo7.atj.le

f l u o r i d e s , t h e combina.tion of

which have lower rr,elt-j.ng p o i n t s t h a n n i c k e l f l u o r i d e .

i t has been r e p o r t e d

24

t h a t n i c k e l f l u o r i d e complexes eaa L1.y anit t h a t m n y combtiiati.ons are known.

A complex o f N i F , and. high v a l e n t chrom-;.i.im P l m i - i d e appears t o be a parti...

cu1arl.y good p o s s i - b i l i t y

.

O f i n t e r e s t i n d i s c u s s i n g ?,he wal.l..-thi~ckness l o s s e s on t h e

Marrk 1 f l u o r i n a t o r i s t h e regi.on s1ightI:j- above t h e s a l t - v a p o r i n t e r f a c e where very low losses were Found. 2?c H.

I n t h i s same region, a r i n g 01deposited m a t e r i a l

J . Z:meI.eus, F l u o r i n e Chemistry 1, .... ..._ (cd. b y J. 11. S i m n s ) , Academic P r e s s , Inc., New York, 1350. I_

7,


- 35 WAC

found a f t e r o p e r a t i o n s .

tained on t h e & p o s i t .

-

U n f o r t i x ~ a t e l y , chemical a n a l y s e s w e r e n o t ob-

However, t h e f a c t t h a t this t h i c k r i n g was p r e s e n t ,

probably continuously d u r i n g operations, i s bel3 eved

'GO

have prevented i n t e r -

a c t . i o n s w i t h t h e n i c k e l f l u o r i d e " p r o t e c t i v e " s u r f a c e f i l m s u.nderrleath and thereby prevented high l o s s e s i n t h a t region.

The reason f o r t h e formation

and cont.i.nued presence o f t h e r i n g i s a s s o c l a t e d w i t h t h e l o w teniperatuu'es tha'i. predominated. i~nt h i s r e g i o n .

The l o c a t i - o n i s between the furnace windings

and t h e tubul.ar-type iieatiiig elements a t t a c h e d Lo t h e upper p o r t i o n of the

vessel.

Also, t h e presence o f t h e furnace s e a l on t h e e x t e r i ~ o rof t h e f l u o r i -

n a t o r a t t h i s s a m elevaii.on probably affec-Led tempera1;u:re by acti.ng as a s i n k for conducted h e a t i.n t h i s reg.'>ion. h

.

T n t e r i o r I.I._._. ntergramrlar Attack

I n the "as-poli.sbed" condjttion, iiiteri.or s u r f a c e samples from t h e Mark I f l u o r i n a t o r showed no s i g n of i n t e r g r a n u l a r corrosj-ve a t t a c k .

After

e t c h i n g with a s t r o n g a c i d s o l u t i o n , a mix.ture o f O.5$ HCI, approx )-IO$â&#x201A;ŹIN0 a n d apprclx

60%

HC H 0

3'

t h e s u r f a c e g r a i n boundaries t o depths of from 1k-25 m i l s

P 3 2' were a t t a c k e d more s e v e r e l y and. r a p i d l y t h a n grain boundaries c l o s e r t o t h e i n t e r i o r of t h e specimens.

Using a mild e-Lcliant, KCN- (NH4)~Spo8, and p a r t i a l . --

...

r e p o l i s h i n g , a p a l e yellow d e p o s i t was observed a t t h e mating s u r f a c e s of t h e grains.

T'ne appearance o f t h e i n t e r g r a n u l a r attack on Liie f l u o r i i i a i m r wa1.1.s

was di.stinciAy d i ~ f f e r e n tt h a n t h a t produced i-n n i c k e l by f l u o r i n e o r UF

25 an i n i t i a l n i c k e l f l u o r i d e f i l m ) and r e p o r t e d by Sale e t al.

6

(with

c -

Wie forniati on o f grain-boundary compounds o r obher changes i n

graj.a-boundary regions,

such as t h o s e observed, and. which a r e g e n e r a l l y cs-Lego-

y.i-zed a s i n t e r g r a n u l a r corrosion a t t a c k , o f t e n r e s u l t i.n 'the loss o r "sloughing"

of entire g r a i n s fsom tile exposed s u r f a c e of t h e m a t e r i a l ,

Rowever, m e t a l l o -

g r a p h i c exami.nations o f specirnens from t h e f l u o r i n a t o r r e v e a l e d r e l a t i v e l y snioo-Lh s u r f a c e s

.

25C. F. Kale, E.' J. Barber, H. A. Bernha-rdt, and K a r l E . Rapp, High Il'emperature Corrosio7.i Study, I n t e r i m R e ~ ~ o fr ot r t h e P e r i o d November, 1958, -_-_---_-..I__ Through May, I . ~ ~ ~ ; - - K V @ T ( Z28, CL~ 1959). Y


Some circunistari-tial evi.d.ence w a s a v a i l a b l e t o i n d i c a t e t h a t sul.-fur contamination produced t h e grain-boundary rmrlj.ficatio-ns observed.

a d d i t i o n -Lo p r e v i o u s l y r e p o r t e d work

26

In

where micros:;-,,ii.ctures of n i c k r l speci.-

mens purpose1.y ernbri t t l e d w i t h sulfur were compared w i t h e a r l y W P L n i c k e l

coi-rosion specimens, a comriiunication from ORGDP, which s u p p l i e d the VTP w i t h

p r o c e s s f l u o r i n e , i n d i c a t e d t h a t as much as 200 ppm of s u l f u r as s u l f i n y l f l u o r i d e hacl o c c a s i o n a l l y been d e t e c t e d i n t h e i r maiiuEactured f l u o r i n e . Contamination from t h e coumercial sodi im fl.uori.de used t o s t i * i p hydrogen

f l u o r i d e arid water from t h e p r o c e s s f l u o r i n e coi.ild a1.m be a source of s u l f u r .

S u l f u r could a l s o be i n t r o d u c e d into t h e system from impure f e e d s a l t s o r from t r a c e q u a n t i t i e s containec? i n c o r r o s i o n Lest speci.mens.

Attempts t o prove t h e presence of s u l f u r i n L h e ::luorinator w a l l samples i . n q u a n t i t i . e s greatei- t h a n tMt; p r e n z n i i n iiie base metal by u s i n g su1fu.r p r i n t papers, chemical anal.yses o f s u r f s c e rni~l.J.ingsand w a l l d e p o s i t s , bend t e s t s , and various uietaTl.l.o~.L.aphi_c teclhiij~quese i t h e r met w i ti1 f a i l u r e o r produced inconeLusi.ve r e s u l t s .

Thi.s was p a r t i c u l a r l y Trustrati.iTg

i n v-iew of e a r l y r e p o r t s t h a t f r e e N i S had. beell i d e n t i y i e d i i i nFckel micro3 2 28,29 scoyi.cally when 0-05 and 0.005 wt $I S, r e s p e c t i v e l y , were p r e s e n t . Exalll-

i n a t i o n of 'ihu nickel-sul.Wxr constit;uti.oii d.liag:ram indi-cated that Ni. 5: would 32 be the compound t o seek i.n i d e n t j - f y i n g low p e r c e n t a of sulYi.ir coatarfilnation 7

i n n i c k e l . 30

It w a s considered t h a t chromiuni and/or o t h e r s y s t e n contamina_n-ts

may have complexed t h e Ni S described me?,iiod.s.

32

a n d t h u s prevented i d e n t i f i c a t i o n by some o f the

However, consi-dering the e x t e u s i w e f f o r t s empI.oyed on t h e

f l u - o r i n a t o r s a m p k s , i f sulfur were the tnajor agent responsi-bie f o r t h e i n t e r -

g r a n u l a r a t t a c k , more posit-i.ve i - n d ~ i c a t i o n sshould have been found.

26L. R . T r o t t e r and E. E . Hoffniao, Progrpss H e p o d on V o l a t i l i t y P i l o t

.--_ PlariL Corrosion Problems t o A p r i l 21,-- ..... 1957, .. 0 7 c. I

ORNL-2493

( S e p t p m n b e ? - - ~ ~ ~ ~ .

11. J. Cu.llbert, Process Engineering Division, OEGDP, P r i v a t e communi c a t i o n .

28

G. Masing and I,. Koch, Z . Metal1.k.urid.e

29

2,278-279

(1gPr7).

I

1'. D. bkrrica and R. .C; Waltenberg, T'rans. Met. S o c . APME N a t i o n a l Bureau of Standards Technical Paper 281, 1 5$y& -57 1 _ 1

3A

71 709-71.6 (1925);

-'"M. Iiansen a n d K. Alidcrko, C o n s t i t u i i o n of Binat.y Alloys, p. McGraw-Hi 11, New York, 1958.

1035,


- 31

-

'The n a t u r e o f t h e grain-boundary deposri-ts may n o t be d e t e r -

mined u n t i l t h e y a r e s t u d i e d by an e l e c t r o n probe microanalyzer QT some oLher TJever.l;lieless, because o f t h e p o t e n t i a l effec-t; on c o r r o s i o n and

precise tool.

t h e cumulative and i r r e v e r s i b l e e m b r i t t l i n g t e n d e n c i e s o f t h e ni-ckel-nickel s u l f i d e e u t e c t i c , r e d u c t i o n o f s u l f u r i n VPP n i c k e l f l u o r i n a t o r ' s environments t o the lowest possi-ble l e v e l s i s e s s e n t i a l .

Exterior I n t e r g r a n u l a r Attack

e.

I I -

A s dpscribed, t h e e x t e r i o r of t h e Mark 1 fluorinator s h e l l

a l h o s u f f e r e d i n t e r g r a n u l a r a t t a c k , b u t t o a l e s s e r degre? thau the i n t e r i o r . P e n e t r a t i o n on t h e e x t e r i o r s u r f a c e s v a r i e d from 3-8 m i l s . o f t h i s a t t a c k a t high magnification,

The apL)earancc

t h e e x t e r i o r environment, and t h e

found on the second VPP f l u o r i n a t o r o p e r a t e d under similar 2 c o n d i t i o n s , i n d i c a t e t m i . c a l high- t,emperature inLergranular o x i d a t i o n o f

preseiicr of N i O nickel. d.

Grain- S i z e Var..i.ations Metallographic examination of samples removed from t h e s h e l l

o f t h e Mark I f l u o r i n a t o r discl.osed widely v a r i a n t g r a i n s i z e s . g r a i n s of

5-6

Small, iiniyorm

average ASTM g r a i n - s i z e number p r e v a i l e d i n t h e s a l t and salt,-

vapor i n t e r f a c e regions, w'nil-e much l a r g e r g r a i n s were observed i n most of t h e

vapor region.

The l a r g e s t grai.ns found i n t h e vapor regiori were a t

ti.on of approx 12 i n . below t h e bottom of t h e s l i p - o n f l a n g e .

eleva-

The average

ASTM graj-n-size nurflber a t t h e 12 i n . e1evat;ion w a s g r e a t e r t'nan 1.

eter

at:i.

Di.ffractom-

t r a c e s were o b t a i n e d on vessel samples removed from t h e 1-, 12-1/2-,and

43-in. l e v e l s i n o r d e r t o compare t h e r e s i d u a l s t r a i n remaining i n t h e samples. The r e s i d - t s i n d i c a t e d approximately no recrystalli.zal;i.on h a d occurred a t t h e

1-in. level, only a very l i m i t e d amount o f r e c r y s t a l l i z a t i o n took p l a c e a t the lP-l/P-in.

level-, and p a r t i a l , i f not complete, r e c r y s t a l l i z a t i . o n occurred

i n the s a l t - p h a s e sample.

The c l a s s i c a l . f a c t o r s which determine c r y s . L a l l i t e growth upon

heatj.:ng a r e amount of p r i o r c o l d d.eformation, anneali.ng temperature, and

a n n e a l i n g -time: Gener-ally, l a r g e r arnouiits o f c o l d deformation provide f o r


s m a l l e r resul.iaiit g r a i n sizes a f t e r isotilermal. and c o n s t a n t t i m e mneal.ing. Higher -Leniperatures and, t o a k s s e r degree, longer times r e s u l k i n 1-arger p a l n s i z e s on m a t e r i a l containfny; some fi-sed amount of c o l d work.

I n maiiy ma-ierials a small amoun-t o f p r i o r co1.d deformation

r e s u l t s i n Lhe prod.ucti.on of exaggerated gi-ai.ns a f t e r a.iineaLing at o r d i n a r y t i m e s and temperatures.

1111

t h e s e cases, t h e t e r m " c r i t i c a l . sti-ai.n" has been

given t o t h e quan"i,ity of c o l d work o r l g i n a l l y in-traduced.

i.nvolved here have been s t u d i e d and r e p o r t e d i n detai.1. 31

The mechanisms

The VPP Mark I fluorilia-Lor was f a b r i c a t e d from L n i c k e l by

conveyting a f l a t , annealed, l / h - i n .

by roll forming.

p l a t , e i n t o a 14-in.-diam

righl; c y l i n d e r

During forming, cold. deforma-tion was induced i n t h e o u t e r -

most f i b e r s or t h e shell t o a c a l c u l a t e d maxi.iiiurn of approx 2%.

This amount

oi? cold work i s a t t h e r i g h t level. t o 'ne termed " c r i t i c a l . strai:rll' I"or most

metals and presumably was pyeseiit along t h e e n t i r e lengbil o f -the fl.uori n a t o r shell.

Howe-ve.r, exaggerated g r a i n s i z e s were observed o n l y i n a p o r t i o n o f

phase of t h e v e s s e l a f t e r p i l o t p l a n t operatTons.

tihe vapo:r

Therefore, an.

a d d i t i o n a l vayiabI.c, r a t e of h e a t i n g a f t e r p r i o r deformatlon, has been sug-

ges-Led as the most i.nfluenti.al f a c t o r i n prodircihg t h e grai.n s i z e s found i n t'he Ma&

.

i flimrri n a t o r 32

The f i r s t time t h e fluor'inator w a s heaLed was dui.i~ngpre-

l i m i n a r y fluoi.iiiat,i on equipment s t u d i e s .

-During those c y c l e s , t h e lower

23 i n . of t h s v e s s e l w a s surrounded by a iliigh h e a t - f l u x 30-k1.r e l e c t r i c -

r e s i s t a n c e furnace which rai-sed t h e t e q x r a t u r e o f the enclosed p o r t i o n of t h e v e s s e l t o approx

450째C.

No external. h e a t or i n s u l a t i o n was i n c l o s e

proximity w i t h t h e upper porti.on o f t h e f l u o r i n a t o r .

the same p r e l i m i n a r y stud.i-es were done w i t h

%I

coveri-ng t h e t o p p o r t i o n s of -tile f l u o r i i i a t o r . gions o f the v e s s e l reached

L a t e r c y c l e s duri.ng

g;i.ass-Iii-ied heati.ng mantle Temperatures i n t h e lower re-

600-700째C, w h . i l e 'ieniperatures i n t b e ilppei- r e g i o n s

of t h e v e s s e l were much lower.

.

37 J E Burke, "The Ebndarwntal s of R e c r y s t a l l j Lsl,ion a n d G r a i n Growth, G r a i i i Co i t r o l i n I n d u s t r i a l Metallurgy, Arneri-can S o c i e t y fo-t. Metals, Cleveland, _--..

Ohio, l9k9.

~

"L, K. J c i t e r and C. J. McHargue, ORNL Metallurey Divisjon, P r i v a t e comm-unication.

.


- 3Y

-

I n vi.ew of t h e i n i t i a l Mark I h e a t i n g c y c l e s , and confirmed by the d l f f r a c t o m e t e r t r a c e s , t h e s a l t r e g i o n o f t h e T l u o r i n a t o r appears .Lo have experienced thermal l e v e l s where recovery and a t leas-t, p a r t i a l . r e c r y s t a l l i z a t i o n occurred

The r e c r y s t a l l i z a t i o n teuiperature f o r ni.ckel v a r i e s from

apip.-ox 600째C f o r A nickel.,

99.4

p u r i t i - e s of' e l e c t r o l y t i c n i c k e l ,

$ ( N i i- Co) t o 370--'~70"Cf o r i99.9 Fi-t 4 ( N i -I- Co) a f t e r 50%

wb

various r e d u c t i o n by

c o l d rolli..ng and. annealirig f o r 1 h r a t t h e temperature indi-cated. 33

Jetter

and Mc:-Iargue have suggested t h a t d u r i n g t h e i n i t i a l h e a t i n g the r a p i d rake

of h e a t i n g d i d noL all-ow complek r e l i e f of i n k r n a l stresses which at; h i g h e r

temperatures served as n u c l e a t i o n s-iten for r e c r y s t a l l i z a t i o n .

Tne r a t e of

''

appearance of t h e s e n u c l e i i s know71 t o i n c r e a s e w i t h time, exponenti.ally with

temperature, a n d w i t h i n c r e a s i n g amounts of p r i o r cold deformation.

After

n u c l e a t i o n , s t a b l e nucleus growth occurred. and t h e presence of so many g r a i n s growing i n a f i x e d vol.ixne l i m i t e d t h e s a l t r e g i o n g r a i n s i z e .

L a t e r heat

c y c l i n g of t h e f l u o r i h a t o r was done at approximatkly t h e sal;.ie temperatixre

levels as t h e hi.g'nest o r i g i n a l heati-ng ( 6 0 c y 2 5 ~ c )s o t h a t probably l i - t t l e , i f ' any, grai-n-boundary rni.gration occurred a f t e r r e c r y s t a l l i z a t i o n t o i n c r e a s e t h e

grain s i z e i n t h e I-ower p o r t i o n s of t h e v e s s e l . The top h a l f o f t h e Mark I f l - u o r i n a t o r sustai-ned lower tempera-

t u r e s d u r i n g t h e f i r s - t h e a t c y c k s as t h e r e s u l t o f h e a t l o s s e s by r a d i a t i o n and convectlon f'rom t h e upper p o r t i o n s of t h e v e s s e l wall.

terflperature of

<

A steady s t a t e

200째C a t t h e 1 2 - i n . l e v e l l?as been

The upper

porti.ons of the vessel. a l s o experi.enced sluggi.sh h e a t i n g r a t e s when compared

t o t h a t p o r t l o n o f -the vessel enclosed b y t h e h e a t i n g flmnace.

It has been

suggested t h a t t h e l a t t e r influenced- t h e g r a i ~ ns i z e i n the vapor r e g i o n by

permi-tting more complete recovery and r e s u l t i n g i.n few n u c l e a t i o n s i t e s . k r i - n g l a t e r o p e r a t i o n s i n t h e p i l o t p l a n t , rod-type e l e c t r i c h e a t i n g elements w i t h a t o t a l r a t i n g o f 9 kw were i n c o n t a c t with t h e vapor

3%, M. Wise and R. H. Shafcr, "The P r o p e r t i e s of Fure Nickel - I, I T , 111," Metal..:; and Alloys, Sepi., p . lC24, Nov., p. 891, Dee., p. 1067, 1942. I

34S. 8. S t a i n k e r , ORNL, Chemical Technology Division, P r i v a t e comflunication.


.

r e g i o n e x t e r i o r surYaces of the f l u o r i n a - t o r

A therriocouplc at; approxj-mately

t h e 12-in. l e v e l ind-icated average temperatures of 400째C and a inmimum o f 500째C.

Such thermal l e v e l s p e r m i t t e d o n l y a sinal-l_ amount o f r e c r y s t a L l i z a t i . o n

bo occur, as i.ndi.cated by t h e d i f f r a c t o m e t e r s-Ludies.

A.n exti-emely coarse

g r a i n s i z e r e s u l t e d from t h e d e s c r i b e d c o n d i t i o n s .

Examination of samples removed from t h e Mark

I fluorinatoy

r e v e a l e d Ynat the m e t a l - l o s s p r o f i l e and g r a i n - s i z e p r o f i l e c l o s e l y p a r a l I.eI.ed one a n o t h e r except f o r t h e r e g i o n j u s t below t h e t o p f l a n g e oi? t h e vessel.

3ecause of t h e evidence o f corrosi.on by i n . t e r g r a m l a r a t t a c k during

exposure t o t h e v o l a t i l i t y f l u o r i . n a t i o n environiiient, a c a u s a l r e l a t i o n s h i p

i s suggested.

Thus, loss of a l a r g e g r a i n by e f f e c t i v e l y l o s i n g graj-n-boundary

material u n t i l t h e g r a i n sloughs o f f wou1.d mean g r e a t e r l o s s e s t h a n for the same procedui-e happening i n f i n e - g r a i n r e g i o n s

However, sloughing of gra-ihs

was n o t observed and o n l y a sl-ig'nt widening o f tile boundarrtes was no-Led a t t h e j u n c t i o n of the bouiidarries and the exposed metal s u r f a c e s .

Also; the

d e p t h o f inte-rgranular p e n e t r a t i o n i n c o a r s e - g r a b r e g i o n s w a s aboui; the sam

a:; i n most of t h e f i n e - g r a i n r e g i o n s .

The concl.i~sioni.s t h a t me'ial. loss and

grai-n si.ze do no-t seem t o be i n t e r r e l a t e d i n t h e c o r r o s i o n o f t h e Mark 1 fluorinator.

HoTvever, for two reasons, t h e a u t h o r s recommend using f i ~ n e -

g r a i n e d material f o r f l u o r i . n a t i o n v e s s e l s .

One, a h i g h e r s t r e n g t h l e v e l w l l l

be achieved i.n n i c k e l , a material n o t noted f o r superi.or s t r e n g t h ; and. t w o , one varlab1.e w i l l be removed i n a system r e p l e t e w i t h v a r i a b l e s .

Pine-grained

materia.1. can be provided by modificatj.on o f t h e s p e c i f i c a t i o n s of purchased s t o c k and by r e v i s i n g t h e anneali.ng c y c l e a f t e r fa5rj.cati.on. 35

311. Mark I1 V o l a t i l i t y P i l o t P l a n t L Nickel Fluorinator A. Materia,l S e l e c t i o n and Fabrication-Design ... _. _. . Changes While L n i c k e l seemed d e f i c i e n t i n i t s c o r r o s i o n r e s i s t a n c e f o r long-

-time s e r v i c e , no o t h e r con~iierciallya v a i l & l e mat,erial. had, a t t h a t t h ~ proved , ""Anneal.i.ng o f Nickel, Monel, and Inconel, I' Tech. Bull. T-20, The In-LemaLional Nickel Compan.y, Inc *, N e w York, A p r i l , 1.953.


- 41 i t s e l f on t h e basis o f s c o u t i n g o r o t h e r t e a t s t o be worthy of immediate sub-

s t i t u t j - o n as a f l u o r i n a t o r m a t e r i a l of c o n s t r u c t i o n .

Moreover, t h e heavy

vapor-phase a t t a c k on the Mark T f l u o r i n a t o r was s t i l l under i n v e s t i g a t i o n ,

so t h a t t h e u s e o f t h e same construct?.on m a l e r i a l seemed e s p e c i a l l y a p p r o p r i a t e

t o a s c e r t a i n more a.bout t h i s c o r r o s i o n p r o b k m .

Consequently, the Mark I7

?'luorj.nator was f a b r i c a t e d i.n t h e QHNL shops from t h e same h e a t oi" l / k - i n . -

t h i c k L n i c k e l as w a s used i n t h e previous p i l o t p l a n t v e s s e l . f a b r i c a t i o n technri ques were used.

Figure

13 shows

Analogous

t h e second VPP f l u o r i n a t o r ,

t h e v e s s e l furnace, and t h e cornplexible radi.oacti.ve products ( C F P ) t r a p . C e r t a i n d e s i g n changes were i n c o r p o r a t e d i n t h e second p i l o t pl.ant Pluorina-Lor.

I n o r d e r t o provi.de f o r remote h m d l i n g and t o allow d e s i r a b l e

upward flow through t h e CRP t r a p ,

i.ts l o c a t i o n was changed from t h e o r i g i n a l

si.& p o s i t i o n shown i n Fig. 1 t o an e l e v a t i - o n completely above t h e Mark I1

fluorinstor.

Other p r o c e s s design changes included some m o d i f i c a t i o n OF t h e

draCL tube assembly, r e p o s i t i o n i n g of t'ne off-gas l i n e , and t n s t a l l a t i o n o f a

sinall p o r t i.n t h e t o p blind. f l a n g e of t h e f l u o r i n a t o r f o r o b s e r v a t i o n and e n t r y .

R.

b e r a t i o r i a l History

The Mark I1 fl1.aorinator was placed i n s e r v i c e a t the beginning of

t h e '!EE1 runs durring wh.ich t i m e f u e l used. i n t h e A i r c r a f t Reactor Experiment

was reprocessed. 3'-7 The use of t h e v e s s e l w a s continued d u r i n g t h e "L" (oyiked) mns and during t h e gas-entrainment s t u d i e s , history,

M-62 through M-64. The process

summarized i.n Table V I , has been d i v i d e d i n t o t h r e e phases f o r con-

venience i n r e p o r t i n g t h e Vidigage i n s p e c t i o n s on t h e v e s s e l a t th.e completion

oP Runs L-It and L-9.

''

The "L" o r s p i k e d runs were made i.n t h e VPP t o extend process develop-

ment da-ta and used a n o n i r r a d i a t e d s a l t w i t h F u l l y enricb.ed. u.ranium.

Some

36F. W. Miles and 17. 11. Carr, Engineering E v a l u a t i o n of V o l a t i l i t y P i l o t P1.ant Equipment, CF-60-7-65, pp. 43-145. I -

n-

j f W . H. Carr, V o l a t i l i t y P r o c e s s i n g of t h e ARK Fuel,

14, 1958).

I

CP-;8-11-60 (November

38C. L. Whitmarsh, Uranium Recovery from Sodlum Zirconium Fluol-7.d.e S a l t Mi.xtures, V o l a t i l . i t y P i l o t Pla111; lhns L-1 Through L-9, CF-59-9-2 (September

30, 1959).

--

36


- 42 -

Unclaesified

ORNL Photc

Fig. 13.

45554

Mark I1 WP F l u o r i n a t o r and CRP Trap.


Table V I .

Summary o f Process Conditions for Mark I1 V o l a t i l i t y P i l o t P l a n t F l u o r i n a t o r Vpp f?E,ff ffL,f! and "Mfl (62-64) Runs

,

Temperature O C Thermal c y c l e s Time of exposure a t tempera t u r e , s a l t s molten-hr Fused salt, nominal mole %

Phase I Runs E - 1 Through E-6; L - 1 Through L-4

Phase I1 Runs L-5 Through L-9

-

10

900

~ 1 - ~NaF-ZrF, 6 -UFL (c, d)

4535 i n 18 hr (2.8-6.9 s t a n d a r d

Conditioning f l u o r i n e a input, s t a n d a r d l i t e r s

l i t e r s/min) 44 470 i n 74 h r (1.6-20.2 standard liters/min)

Operating f l u o r i n e i n p u t , standard lit e r sb

25

UF6 exposure, h r

Total

60~-690 17

54G7 30

-

Phase I11 Runs M-62 Through M-64

725

NaF-ZrF4

( 5G501 750 i n 3 h r standard l i t e r s/min) 16 000 i n 18 h r

(2.5-7

-

10

none none

none

5285 i n 2 1 hr (2.5-7 standard

Iiters/min) 60 470 i n 92 hr (1.&20,2 s t a n d a r d l i t e r s /min )

-

I

& I

35

aThese o p e r a t i o n s were done a t '2G150째C f o r t h e purpose of inducing an i n i t i a l " p r o t e c t i v e " f i l m o f n i c k e l f l u o r i d e on t h e walls of t h e f l u o r i n a t o r . bAn average of approx 3 : l excess F2 over t h a t q u a n t i t y necessary f o r t h e o r e t i c a l requirements was used i n o r d e r t o reduce t h e f i n a l uranium c o n c e n t r a t i o n i n t h e s a l t t o a few p a r t s p e r m i l l i o n , CUranium was f u l l y enriched. Feed s a l t s contained t h e following ranges of i m p u r i t i e s : Component: 0.031-0.056 wt % C r , 0.017-0.138 wt $ N i , 0.033-0.078 wt % Fe, 0.0015-0.080wt $I Si, < 0.001- < 0.005 b r t '$ Mo, dC. L. Whitmarsh, Reprocessing o f ARE Fuel, V o l a t i l i t y P i l o t Plant,Runs E-1 and E-2, CF-59-5-108, (May, 1959) and Reprocessing of ARE Fuel, V o l a t i l i t y P i l o t P l a n t , Runs E - 3 and E-6, CF-59-8-73 (August, 1959). Feed s a l t s contained t h e following ranges o f i m p u r i t i e s : eTen milligrams of puF4 added i n Run L-3-4. Component: 0.0183-0.0345 w t % C r , 0.035-0.236 w t % M i , 0.013~0.030 wt '$ Fe, < O.OOl-O.OO5 w t '$ Si, < 0.001- < 0.0052 wt '$ Mo, and 0.010 wt % T i for L-l,-3, and -5 only. n

-

IC. L, Whitmarsh, Uranium Recovery from Sodium-Zirconium F l u o r i d e Salt Mixtures, V o l a t i l i t y P i l o t Plant,Runs L - 1 Through L-9, CF-59-9-2 (September 30, 1959).

gUranium was f u l l y enriched. One gram of FuF4 added i n Run L-6; 10 grams of PuF4 added i n Bun Same f e e d s a l t i m p u r i t i e s and r e f e r e n c e as d e t a i l e d i n ( d ) above.

L-8.


-

44 -

of t h e runs were s p i k e d w i t h h i g h burnup s a l t , t h u s t h e name of t h i s series.

During t h r e e of t h e "L" runs, s e l e c t i v e a d d i t i o n s of

puF4

were added t o the

r e e d s a l t so as t o g a t h e r information on t h e behavior of plutonium i n t h e Previous experiments had i n d i c a t e d t h a t some v o l a t i l i -

v o l a t i l i t y p r o c e s s . 39 z a t i o n of PuF

6 would

occur.

However, g r e a t e r t h a n

99% o f t h e plutonium

remained i n t h e s a l t i n t h e f l u o r i n a t o r during t h e "L" runs.

S e v e r a l months a P t e r t h e "L" r u n s were completed, t h e Mark I1 f l u o r i -

n a t o r w a s used t o s t u d y gas-phase entrainment problems i n t h e VPP.40

runs, M-62 through phase.

M-64, i n v e s t i g a t e d

Barren equimolar NaF-ZrF

w a s not present. C.

These

ZrF4 s o l i d condensation i n t h e vapor

4 s a l t was used i n t h e s e s t u d i e s and f l u o r i n e

Reaction t o Environment

1. V i s u a l and Vidigage I n s p e c t i o n s During t h e f i r s t p o r t i o n of t h e "L" runs, 1 through

l i n e plugging occurred.

4, p e r s i s t e n t

Presumably t h i s w a s due t o n i c k e l contamination i n

t h e Peed s a l t s p l u s c o r r o s i o n l o s s e s which allowed t h e c o n c e n t r a t i o n of n i c k e l f l u o r i d e i n t h e s a l t t o exceed t h e s o l u b i l i t y l i m i t .

After run

L-4, t h e

plant

w a s s h u t down and approx 200 l b of a high-melting s a l t complex w a s found i n t h e bottom of t h e Mark I1 f l u o r i n a t o r .

See Fig.

14.

P e t r o g r a p h i c and x-ray

d i f f r a c t i o n a n a l y s e s showed t h e mass t o c o n t a i n 20-30 w t

50-60

wt

%

NaF-NiF2-2ZrF4.

$

NiF

2

and

I n o r d e r t o continue u s i n g t h e v e s s e l , t h e f r o z e n

s a l t w a s chipped o u t w i t h a pneumatic hammer. R e s u l t s of a v i s u a l i n s p e c t i o n of t h e Mark I1 VPP f l u o r i n a t o r

a f t e r exposure t o "E" and L-1 through

cited:

Vessel walls

L-4 r u n s

and cleanup o p e r a t i o n s are

Free of s a l t on t h e i n t e r i o r . E x t e r i o r s u r f a c e s were covered w i t h a d u l l g r a y f i l m . Those p o r t i o n s of the w a l l n e a r t h e g i r t h weld had s c a r s on t h e i n t e r i o r surf a c e s presumably caused by g l a n c i n g blows of t h e pneumatichammer blade

.

39R. A. Cross and C. L. Whitmarsh, Plutonium Behavior i n t h e F l u o r i d e V o l a t i l i t y Process, CF-59-9-5. I. 4v J. B. Ruch, V o l a t i l i t y : F l u o r i n a t o r Design FV-100, Z r - U F u e l Element P r o c e s s i n g Phase, CF-59-5-89. n


- 46 Longitudinal seam weld

I n t e r i o r s u r f a c e s were s h a r p l y d e f i n e d by c o r r o s i v e a t t a c k . Corrosion of t h e weld metal (INCO 61) appeared t o have been as s e v e r e or more severe t h a n t h a t of t h e w a l l (L n i c k e l ) .

G i r t h weld

I n t e r i o r s u r f a c e s were s h a r p l y d e f i n e d by c o r r o s i v e a t t a c k . Corrosion of t h e weld metal ( I N C O 61) appeared t o have been as s e v e r e o r more s e v e r e t h a n t h a t on t h e w a l l or t h e dished head.

Dished head

I n t e r i o r s u r f a c e s e x h i b i t e d many s c a r s on s i d e s and bottom of t h e head, presumably caused by t h e pneumatic-hammer b l a d e . E x t e r i o r s u r f a c e s were bulged approx 1/16 i n . i n about s i x p l a c e s corresponding t o t h e deeper i n t e r n a l s c a r s .

Vidigage ( u l t r a s o n i c t h i c k n e s s ) measurements were made t o a s s e s s t h e damages d u r i n g s a l t removal p l u s t h e w a l l - t h i c k n e s s l o s s e s t h a t had occurred during previous process cycling.

A maximum w a l l - t h i c k n e s s l o s s of

i n the salt-containing region o f t h e f l u o r i n a t o r .

68 m i l s w a s found

Complete r e s u l t s of t h e

Vidigage examination a r e shown i n Tahle V I 1 along with o t h e r d a t a . Despite t h e high-corrosion l o s s e s i n d i c a t e d , a d e c i s i o n w a s made t o use t h e v e s s e l f o r an a d d i t i o n a l f i v e runs s o as t o complete t h e scheduled p r o c e s s development s t u d i e s . t h e subsequent "L" r u n s

No plugging d i f f i c u l t i e s were encountered during

5 through 9.

This w a s accomplished by d i l u t i n g t h e

f e e d s a l t with an e q u a l amount of n i c k e l - f r e e b a r r e n s a l t . Figure

run L-9.

1 5 shows t h e i n t e r i o r of t h e

Mark I1 f l u o r i n a t o r a f t e r

The r e s u l t s of a v i s u a l i n s p e c t i o n a f t e r hand chipping and decon-

t a m i n a t i o n were as follows: Vessel w a l l s

Free of s a l t on t h e i n t e r i o r . Vapor r e g i o n appeared rough and p i t t e d and had an adherent green d e p o s i t i n t h e r e g i o n 10-20 i n . below t h e s l i p - o n f l a n g e . E x t e r i o r s u r f a c e s were covered w i t h a d u l l gray f i l m . The s c a r s caused by t h e pneumatic-hammer blows a f t e r Run L-4 were s t i l l p r e s e n t .

Longitudinal seam weld

I n t e r i o r s u r f a c e s were more s h a r p l y d e f i n e d by c o r r o s i v e att a c k t h a n p r e v i o u s l y noted. Corrosion of t h e weld metal appeared -Eo have been more severe t h a n t h a t of t h e base

metal.

G i r t h we I d

I n t e r i o r s u r f a c e s w e r e more s h a r p l y d e f i n e d by c o r r o s i v e a t t a c k t h a n p r e v i o u s l y noted. Corrosion of t h e weld metal appeared more severe t h a n t h a t of t h e base m e t a l .

Dished head

I n t e r i o r and e x t e r i o r s c a r s from previous chipping o p e r a t i o n s were s t i l l p r e s e n t .


T&le V U .

Conparison of Vidigage Thickness Readings, i n Inches, a n the V o l z - t i l i t y Pilot l P l a n t Marl; 11 .L ~ i c k e Fliiorinatora

?T. W. Qzadrant M .E, Qdadrant Area B AreE C Area A ( i n . below Heading Reading Reading Reading Readlng Reading after after after after after after slip-on flange) Region RUE L-? Run L-4 Run L-9 Run L-li. Run L-9 3m L-4 0.e48 0.248 0.248 0.250 0.248 5 c 7

I

I

0.250 0.248

-

0.246

-

0.243 0.232 G.230 0.229

0 .248 -

0.235 0.230

0.234

0.225 0,210

-

41 43 45 47

0.198 G.194

o.ig?F 3.296 0.210 0.238

0.247

-

9.224 0.2240.207

0.222 G .224 0,205 0.236

0,221 0.210 0.198

0.196

0.192

G.20b 0.20;

0.230 0.234 0.24-2 0,248

0.240

0.252

0.192

0.234

0.232

-

0.236 0.230 0.227 0.224 0.227 0.242

0.24.6

-

0 250

0.230

O.23'c 0.234

c

0.247 0,242

-

0.2130

0.228

.-

0.234

0.240 -

-

9.23'; -

0.230 0,240

37 39

S .X

S ,Id. @adrant

Elevation

-

0.196 0.198 0.208

0.236

-

-

a Accuracy of readings e s t i m a t e d to be k 0.003 i n .

0.230

-

0.189

0 .167 0 * 184

0.188

0.250 -

0.249 0.248 0.241 0.235 0.234 0.232 0.236

-

0.240 0.230 0.230 0.218 0.204

0.196 0,212 0,215 0 210

0.202

0,20L 0.204

Area D

Reading after

Run L-9 0.250

. Qisdrant

Area E Reading Reading Reading after ayter sfter Run L-4 Run L-9 Run 2-11.

-

0.248 0.250

-

0.250 0.2$

0.248

-

-

-

-

0.238

-

0.238

9.234 0.236

-

0.236 0.2lcG

-

-

-

0.230 0.226 G.210

0.230 0.222

0,198 0.193 0.189 0.136

0.206

0.195

0.192

0.192

0.198

0.194

0.238

0.236 0.228 0.202

0.1186

0,243

o.iyiC.184 0.184

c

-

0.210

o,igp 0.2gC 0.200

0.196

-


a

-4-8-


- 49

-

Decontamination w a s done by a l t e r n a t e washings u s i n g a mixture of

1.8 M KOH, and 0 . 4 M N a C H 0 a t room temperature and 4 2 4 4 6

0.7 M

H 0 2 2' M (NF4)2C204 a t 100째C.

A t t h a t time Vidigage r e a d i n g s were o b t a i n e d and a r e r e p o r t e d i n Table VII, along w i t h t h e p r e v i o u s r e a d i n g s o b a t i n e d a f t e r Run L-4.

No s i g n i f i c a n t ad-

d i t i o n a l w a l l - t h i c k n e s s l o s s e s w e r e found.

The c o r r o s i o n c o n d i t i o n s e s t a b l i s h e d d u r i n g t h e gas-entrainment s t u d i e s , Runs M-62 through

M-64,

which were done a t a l a t e r d a t e u s i n g t h e

Mark I1 f l u o r i n a t o r , were n o t f e l t t o be s u f f i c i e n t l y s e r i o u s t o warrant a n o t h e r complete Vidigage i n s p e c t i o n . 2.

Chemistry Samples of t h e d u l l g r a y f i l m p r e s e n t on t h e e x t e r i o r w a l l of

t h e Mark I1 f l u o r i n a t o r a f t e r Iiuns L-4 and L-9 were analyzed by x-ray d i f f r a c -

I n a d d i t i o n , samples of t h e adherent, green t i o n t e c h n i q u e s t o be NiO 2. d e p o s i t which remained on t h e i n t e r i o r w a l l of t h e v e s s e l i n t h e vapor r e g i o n were submitted for x-ray d i f f r a c t i o n a n a l y s e s .

The presence of NiF

2,

NiO,

and

Z r O w a s noted. 2 S u r f a c e and s u b s u r f a c e m i l l i n g s were t a k e n from t h e i n t e r i o r w a l l

of t h e v e s s e l i n t h e r e g i o n where t h e green d e p o s i t seemed t h i c k e s t ,

14-17

in.

below t h e bottom o f t h e s l i p - o n f l a n g e , and submitted f o r a d d i t i o n a l chemical analyses.

For comparison purposes, subsurface m i l l i n g s were also t a k e n from

t h e e x t e r i o r v e s s e l w a l l a t t h e same e l e v a t i o n . chemistry are shown i n Fig.

The r e s u l t s of t h e m e t a l

16, and i n d i c a t e an i n c r e a s e i n chromium con-

c e n t r a t i o n i n the m i l l i n g s n e a r t h e s u r f a c e o f t h e i n t e r i o r w a l l of t h e vessel.

No s i g n i f i c a n t i n c r e a s e i n s u l f u r i n t h e vapor r e g i o n o f t h e f l u o r i n a t o r

over. t h a t q u a n t i t y p r e s e n t i n the base material w a s found.

However, on

specimens removed from t h e s a l t r e g i o n of t h e Mark I1 f l u o r i n a t o r , which were

l a t e r analyzed by B a t t e L l e Memorial I n s t i t u t e (BMI), an i n c r e a s e i n t h e s u l f u r

c o n t e n t of t h e i n t e r i o r w a l l specimens w a s noted. results

.

Figure

16

a l s o shows t h e s e


I

L

oz 1 W

s 4

09 1

D r

<

ul

rn VI

OPZ

oz 1

D

%

0 W Z

I

r

z

D r

I

5 rn v,

OP

SP

s9 01 1

s9

OP

ss 1

oz

-f 'U!

61

6S16b 3 M Q - t l l - l N U O Q313lSSV13Nn


- 51

3.

-

Dl.mensiona1 RriaLysis .-A f t e r decontam:i n a t i o n and o t h e r cleanup o p e r a t i o n s ,

samples

were trepanned Crom t h e Mark I1 f l u o r i n a l m r and sent t o BMI f o r dimensional a n a l y s i s and m e t a l l o g r a p h i c examination. d-isplayed i.n F i g .

1-7.

The l o c a t i o n o f t h e s e coilpons i s

I n a d d i t i o n , a f u l l - l e n g t h s e c t l o n from TI-E a r e a ,

s o u t h e a s t quadrant, w a s removed and micrometer measurements t a k e n a t OIIl'sL t o pl-ot a complete c o r r o s i ~ o nprofile o f wal-l-thickness l o s s .

This plot i s shown

i n Fig. 18 and i n c o r p o r a t e s BMI micrometer measurements on t h e trepanned samples from t h e o t h e r qimdrants o f t h e Yluorinator..

For comparison, Vidi-

cage read.ings of t h e D-E a r e a a f t e r r u n s T,-4 and. T.,-9 a r e also p l o - t t e d i.n

u

F i g . 18.

The maximum wall.-thickness l o s s e s Found were i n t h e s a l t r e g i o n

of Mark I1 f l u o r i n a t o r .

111 a r e g i o n 40-43 i n . bel-ow t h e bottom of tile slip-

on f l a n g e of the v e s s e l , a w a l l - t h i c k n e s s l o s s o f 82 m i l s was recorded.

Fair

c o r r e l a t i o n belxeen t h e Vi-digage r e a d i n g s and. t h e micrometer measurements was no-ted

4.

Metallographic S-tudy

R m e t a l l o g r a p h i c study w a s made on t h e trepanned samples from t h e Mark

TI f l u o r i n a t o r by personn.el o f .the RMI Corrosi-on Research Division. 41

At

low magnification, 20X, t h e s u r f a c e s from t h e t o p vapor ( T ) sectli.ons showed a l i - g h t e t c h and some o u t l i . n e oâ&#x201A;Ź g r a i n boundaries.

The mid.dle vapor r e g i o n

specimens ( l a and l b ) were e t c h e d t o a g r e a t e r e x t e n t and were covered w i t h a

t h i n green c r y s t a l l i n e d e p o s i t .

Prevtous chemical a n a l y s e s of t h i s d e p o s i t

at ORNL i n d i c a t e d that, t h e s c a l e c o n t a i n e d NiF,, N i O , and ZrO 2

2'

The vapor-

s a l t i n t e r f a c e (2a and 2 b ) and s a l t r e g i o n specimens (3a and 3b) seemed t o

have been s e v e r e l y etched, and, i n t h e l a t t e r , areas of i n t e r g r a n u l a r a t t a c k could be seen. 'Typical photomicrographs o f s e c t i o n s from t h e Mark I1 f l u o r i n a t o r

can be s e e n i n F i g s . 19 through 2 3 *

I n t e r g r a n u l a r attack w a s p r e v a l e n t i n a l l

"Letter Report from E'. W. Fink, B a t t e l l e Memorial Institu-Le, t o R. P. M i l r o r d , ORNL Subcontract N o . 988 (October 7, 1959).


-

52

-

CELL NORTH

UNCLASSIFIED ORNL LR-DWG 4 9 ( 6 0

S

+VAPOR

F i g . 17. Location of Specimens Xeuloved from the Mark I1 WP L Nickel Fluorinator for Dimensional Analysis and Metallographic Study.


LMCLASSIFIED O R k L- LR- DWG 49964

* I -

___t

t

LENGTH SECTION FROM AREA D-E, SOUTHEAS? QUADRANT

ViDlGAGE SEAD1kGS A F T E R L-4 AREA D-E

A

-

ViDIGAGE READINGS A F T E R i-9 AREA D-E

0

TR E PAN N ED SPEC I MENS

GIRTH WELD-

0

5

10

15

20

25

30

~

35

W A L L TPICKNESS

40

45

LOSS Irnils)

50

55

Fig. 18. Corrosion P r o f i l e of N a k I1 IFP L Nickel Fluorinator.

60

65

70


- 54

-

Fig. 19. M i c r o s t r u c t u r e of Sample f u ~ aI n t e r i o r Surface of Mark I1 VPP F l u o r i n a t o r 3 i n . Below Slip-on Flange (Vapor Phase, Area A ) Etchant: N i t r i c - a c e t i c acid. 1OOX.

.


F i g . 20.

Microstructure of Sample from Jn-terior Surface of Mark I1 Slip-on Flange (Vapor Phase, Area A). Etchant:

VPP Fluorinator 19 in. &Low Nitric-acetic a c i d .

1OOX.


Fig. 21. M i c r o s t r u c t u r e of Sample from I n t e r i o r Surface of Mark I1 VPP F l u o r i n a t o r 31-1 i n . Below SLip-on Flange (Vapor-Salt Interface, Area A ) , Etchitnt: n i t r i c - a c e t i c a c i d . LOOX.

.


F i g . 22. M i c r o s t r u c t u r e o f Sample from Interior Surface of Mark I1 VPP F l u o r i n a t o r 42 i n . B l o w SI-ip-on Flange ( S a l t Phase, Area C ) . Etchant: N i t r i c - a c e t i c a c i d . lOOX.


t

Fig. 23. M i c r o s t r u c t u r e of Sample from I n t e r i o r Surface of Mark 11 WP F l u o r i n a t o r Approx 47 i n . Below Slip-on Flange ( S a l t Phase, Area A) V i c i n i t y of Girth Shell. t o Bottom Head Weld. E t c h a n t : Nitric-acetic acid. 100 x.


- 59

-

s e c t i o n s i.n a l l regioiis b u t p e n e t r a t i o n was deepest i.n t h e samples from t h e i n t e r f a c e and sal-t regions.

Maximurn grain-boundary a.2-ttack was found to be

33 m i l s i n the s a l t - p h a s e sample A-3b which was i n the v i c i . n i t y of t h e s h e l l

t o head g i r t h weld.

Some sl.i.ght vari-a-Lioii i n g r a i n sizes wzs fourid i n the metallo-

graphLc samples.

nator.

The l a r g e s t g r a i n s were i n t h e sa1.t r e g i o n of t h e Yluori-

Table V I 1 1 summarizes t h e grain-si.ze d a t a i n t e x i s of average ASml

g r a i n - s i z e number.

Table ViII. Summary o f Grain S i z e s in Samples Removed from t h e Mark 11 V o l a t i l i t y P i l o t Plant [, Mi cliel F l u o r i n a t o r " I _ -

Location ( i n c h e s dowr~from bottom o f slip-on flange)

ASTM grainsize number

Region

3

Vapor

15 19

Vapor

3-5 3-L 3-1.'

Vapor

29

Vapor- s a l t i n t e r Face

34

Vapor- s a l t i n t e r face

3-5 3-4

J I?

Salt

2 4

47

Salt

2-4

a Grain s i z e s Prom i n t e r i o r w a l l arid exierior w a l l saniplcs were approximately equal. A p i t t i n g a t t a c k w a s Eound

OA

the i n t e r i o r wall near

Area C i n

t h e vapor region, about 3 i n . dowu from the hottom of' t h e s l i p - o n f l a n g e .

Figure 24 shows t h e appearance O S t h e surPaee a t 3X, and Fig.25 shows a metallogr'aiphic s e c t j o n through t h i s pitted area.

The l a t t e r i n d i c a t e s a level of

i n1,ergranular p e n e t r a t i o n simi-lar t o t h a t found i n o thpr upper-vapor r e g i o n s .

The depth of i n t e r g r a n u l a r attack d i d not appear t o vary from top t o 'uottom of

the p i t s .


Unc l.ass i f i e d EM1 N59673

F i g . ? ] i n Photograph of Sample from I n t e r i o r Surface of Mark I1 VPP F l u o r i n a t o r 3 in. B e l o w S l i p - o n Flange (Vapor Phase, Area C ) Showing Vitting-Type A t t a c k . 3X.


- 61 -

Fig. 2 5 . M i c r o s t r u c t u r e of Sample from I n t e r i o r Surface of Mark I1 VPP F l u o r i n a t o r 3 i n . Below S l i p - o n Flange (Vapor Phase, Area C) i n Region of Prftting-Ty-pe Attack. Etchant: N i t r i c - a c e t i c a c i d . 1OOX.


- 62

-

In t h e s a l t r e g i o n of Area C, a few small in-tergranii1.a~c r a c k s

were found on t h e i n t e r i o r of t h e v e s s e l wall.

A typical. crack i s shown i.n

t h e unetched condi.tion i n F i g . 26 a n d i n t h e e t c h e d c o n d i t i o n i.n Fig, 22.

Very pronounced darkening of t h e g r a i n boundaries t o approxi-mately t h e same depth as the crack was evi.dent a f t e r e-tching.

Cross s e c t i o n s from t h e f l . u o r i n a t o r s h e l l longitudi.na1 weld a r e

shown i.n Fig. 27 (Samples B-8T and A-3b) which d e p i c t s s e c t i o n s i.n t h e vapor

and sal..t phases, r e s p e c t i v e l y .

The weld. j o i n t from t h e s a l t regi.on shows

This confirrns t h e

what, appears t o be a n i n c r e a s e d a t t a c k a t tile weld r o o t .

v i s u a l examinations of t h e Mark 11 f l u o r i n . a t o r .

Examination of t h e weld from

t h e s a l t s e c t i o n a t bigk inagnif i c a t i o n r e v e a l e d pronounced grai.n-boundary

darkening a f t e r e t c h i n g t o a maximum depth o f 10 mils,

Similar, deeper g r a i n -

boundary darkening occurred rin t h e base metal a d j a c e n t t o the weld metal, extending t o a maximum depth of 33 m i l s .

The e x ' i e r i ~ o rof t h e vessel d i s p l a y e d a c o r r o s i v e a t t a c k which

appeared t o be i n t e r g r a n u l a r i n nat71re.

P e n e t r a t i.on v s r i e d Prom

1-6

mils, t h e

maximum o c c u r r i n g a t o r below Lhe v a p o r - s a l t i n t e r f a c e (Fig.. 28, Samp1.e A-3b). However, t h e r e w a s one e x c e p t i o n t o t11ri.s pa+,tern.

A grain-boundary peaetrat,ion

of approx 1 2 m i l s i.n depth was found on -the e x t e r i o r s u r f a c e o p p o s i t e tile

p i t t e d r e g i o n i n t h e vapor n e a r Area C.

5.

Summary o f Corrosive Attack ____ Table I X summarizes t h e corrosion l o s s e s of al..l. t y p e s found i n

the t h r e e major r e g i o n s of t h e Mark I1 VPP

L nickel fluorinator.

?'he ma-ximum

a t t a c k w a n cal-culated t o be 60 mils/month based on exposure -Lo molten s a l t s durring t h e VPP "E" r u n s

(1.-6) and "L" mils (1-9)

o r 1.1 rnils/hr based on

f l u o r i n e sparge time d u r i n g f l u o r i n a t i o n of molten s a l t s

e

The maximum a t t a c k

occiirred in t h e s a l t region.

Y.

Discussion o f R e s u l t s The Mark I1 VPP L n j c k e l f l u o r i n a t o r d i s p l a y e d a rnaximurn c o r r o s i o n

a t t a c k d u r i n g t h e d e s c r i b e d VPF runs o f 1.1 mils/hr, based on F sparge time 2 during flixorinaiion, o r 60 mils/month, based on molten- s a l t r e s i d e n c e tiiiie


- 63 -

IJnc I.as sifi.ed m1: c668

FIg. 26. Photomicrograph of Sample from I n t e r i o r Surfac:e of Mark I1 VPP F l u o r i r m t o r Ih2 i n . Below S l i p - o n Flaage (Salt Phase, A r e a C ) Showing Crack E a s i l y Visible Before S e c t i o n i n g . As-polished. 1OOX.


- 64 -

Unclassified BMl ~$9674

i 2,

F i g . 27. Photomacrographs o f Longitudinal Weld Sections Through Wall of Mark I1 VPP Fluorinatol- (a) From Vapor Phase 3 in. B e l o w S l i p - o n Flange, (b) From Salt Phase 47 in. B e l o w S l i p - o n Flange. Etchant: Nitric-acetic acid. 5X.


Unclassl fi.ed BMI cG18

F i g . 28. Mjcrostructure of Stmple f r o m E x t e r i o r Sui-Face o f Mark II WP F l u o r i n a t o r kpprox 47 i n . Below S l i p - o n Flange ( S a l t Phase, Area A) Showing Result of A i r Oxidation. Etchant: ?Xit r i c - a c e t i c a c i d . 1OOX.


Table I X .

LCJc a t i on Elevation (inches below slip-on flange ) Quadrant

3

Summery of Corrosive A t t s c k in Zac?l N a j o r Region of t h e Mark V o l a t i l i - c y P i l o t P l a n t L !lickel Fluorins-tor

77

7

ha ,i

Regi.on

-

T'hickness a loss (mils)

S.W.

1-5

Vapor

S.7.

Vapor

22

19

S.W.

Vapor

25

29

S :w.

Vapor-s a l t

29

N.W.

In2ergrafiulsr Pe ne t r stLon 1n t e r io r EX t e ri o r \,T&ll wall (rniisj (mils)

3

L

7 8

33 36

2G

0.k

22

3.4

28

4

2

39

23

0.4

53

I4

6

75

'L5

0.6

1&

L

77 59

46

0.8

100

60 53

1.1

59

n:.h'.

Salt

52

E.E.

Sslt

82

Salt

45

N.W.

Salt

52

16 16 33 16

Sslt

cj I;

23

N.E.

0.1

0.3

Sslt

47

5

I k 3

18

S.V.

47

8

i

2

6

1

3

84 63 90

e By nitrometer measurement. D

C

time)

30

L2

S.W.

-i;ine)

2

S.W.

L7

(miisj

8

34

42

T o t a l l o s s e s converted

Tot&: t o m i l s / u n i t :i2? b m i 1s/hrd c orro s~ v e nii s /noK t c. ztteck (molten s a l t (F sparge

23

Tnter-Cace V z - 0 ~s- a l t in%erf ac e V q o r - sal-t interface

42

IT

Includes e x t e r i o r L n t e r g r a m l a r p e n e t r a t i o n .

Based on molten s a l t residence t i n e during VPP E(l-6)

runs and L(1-9) r m s .

%asea on f l u o r i n e sparge t i n e curing f l u . o r i n a t i o n o f niolten s a l t s .

i; i

Ll

54

1

m e\ I

0.75 0.9

0.75 1.0


during STP "E" runs

(1-6)

and "L"

TUJX

(1-9).

Maximum a t t a c k occurred i n the

s a l t - p h a s e r c g i o n of' t h i s v e s s e l whereas t h e first VPP Yluorinatoy experienced

ma.ximum losses ri.n t h e vapor-phase rey;i.on,

w e r e of t h e sane o r d e r s of magnitude.

'Irk rates of attack f o r both vessels

'The cori-osi.ve a t t a c k i n t h e Mark I1

Pluorrinator, a8 wa,s t h e case f o - r t h e Mark 1 v e s s e l , can be c a t e g o r i z e d i n t o

bulk

irietal

losses from t h e i n t e r i o r wall. of .the ~ e s s e and l intergranular a t -

t a c k on b o t h t h e i n t e r i o r anti exter-ior walls of the u n i t .

1. I n t e r i o r Rulk Losses Bulk n e t a l lasses a r e b e l i e v e d t o be the r e s u - l t of continuous l o s s and. reformation o f 7vpr~.Li3ctive" NiF

fl.uorinator.

2

f i l m s on t h e i n t e r j - o r w n l l of the Mark 11

A s d i s c u s s e d i n S e c t i o n I, the n l c k e l f l u o r i d e films i"ormer3 on

t h e walls of t h e v-olati.li.ty flizorina,tors durlng c o n d i t i o n i n g and. f l . u o r i n a t i s n

operations could be removed by t h r e e and p o s s i b l y f o u r methods.

Taese a r e :

removal (1)by m-pturin.g o r s p a l l i n g , (2) by a f l u x i n g a c t i o n of t A e Yluoride s a l t baths,

( 3 ) b y a -mshi.ng a c t i o n of t h e m e l t s , and (4) by d i s s o l i r t i o n i n

certain h i g h l y c o r r o s i v e 1j.quids condensable i n t h e c o o l e r regions of t h e

vessel,

Maximum losses occurred in t h e s a l t r e g i o n oz" t h e Mark. I1 v e s s e l

whlich seems t o ind-icate that t h e f l u x i n g a c t i o n of t h e f l u o r i d e bat,hs was t h e

predoniinant method of removing t h e p r o t e c t i v e fil.ms Prom the w a l l s of t h e fhzorin.ator.

fluorinator

The high vapox. r e g i o n s losses d e s c r i b e d f o r t h e first VPP

were p a r t i a l l y a t t r i . b u t e d t o the presence of corrosive L t y u i d s

which condensed. i n t h e c o o l e r regions of that vessel. and some di.scussion o f whether s i m i l a r l i q u i d s i r e r e presenl; i n t h e second v e s s e l seems i n o r d e r .

Evidence of the presence o f -these con-d~ensable 1.iqui.ds i n the

rnl rlrlle vapor r e g i o n s of b o t h 'vessels were (1)the tenar:i,ous ml.1 d-eposi-ts,

( 2 ) t h e segregation of chromium i n surface a n d subsurface l a y e r s , and

However, t h e bulk metal l o s s maximum i n tile second v e s s e l occu.rrzd a few inches below that of t h e i n i t i a l f l u o r i n a t o r .

( 3 ) the bulk m.etal l o s s maxima.

O n e major di.ssi.milari.ty found was t h e lack o f uranium s e g r e g a t i o n

in t h e vapor pha:je of t h e Mark. T I v e s s e l wliZch vas i n c o n t r a s t t o . t h e ? behavior

of -the f i r s t f l u o r i n a t o r .

This l a t t e r f a c t may suggest -the reason :ror t h e


l e s s e r middle vapor r e g i o n a t t a c k i n the second f l u o r i n a t o r when compared with

Perhaps t h e a d d i t i o n a l o p e r a t i n g ex-perieiice of t h e VPP

t h e firs-L v e s s e l .

p e r s o n n e l p l u s t h e modi.fications i n t h e v e s s e l ' s i n t e r i o r p h m b i n g and ext e r i o r appendagps p e r m i t t e d UF

4 to

remain i n t h e sa7.t b a t h s u n t i l more o r

l e s s compl.ete oxidati.on t o v o l a t i l e UF

6 had

occurred..

The w a l l - t h i c k n e s s - l o s s p r o f i l e OT t h e Mark IT f l u o r i n a t o r shows smaller, maxi.mm a t a p o i n t 25 i n . below t h e bottom o f t h e

911 ad.ditiona!.,

sl.Sp-on f l a n g e .

This ai3dit;ional peak i n t h e upper- iii-terfacc r e g i o n i s

b e l i e v e d t o have becn induced by low ope:eational.. temperatures a f e w i n c h e s

below tile 2 5 - i n . level..

There was no d i r e c t methoci 0-f heai; a t

t h e bottom of tile sl-ip-on f l a n g e .

28 i n .

below

This r e g j o n w a s betwzen t h e f u r n a r c

windings used t o h e a t iiie s a l t regior, and t h e rod-iyqx h e a t i n g el.emeiits used

to heat, t i e vapor regi.on.

I n a d d i t i o n , t h e furnace s e a l was p r e s e n t a t i n i s

p o i n t , r e s u l . i i n g i.n a b u i l - i - i n h e a t s i n k .

Thus, t h e c o r r o s i o n p r o f i l e curve

probably would have continued i n a smoo-iii cu.rve f r o m t h e 25-in, e l e v a t i o n on

Ciown toward t h e s a l t r e g i o n except f o r t h i s low- 'cernpei~aturer e g i o n c i t e d . s i m i l a r I.ow-corrosion a r e a was found

a t approximnl;? 1-y t h e sa.me e l e v a t i.on

jinL the

A

im1.l. oC the Mark I i'l.uorinator

I

The corrosion .l.osscs Touncl 3.n t h c sa1.t regfon of t h e Mayrk Ti1

f l u o r i n a t o r were 'die maximum fouiid in t h e sys-Lem and on t h e o r d e r o f twice

t h a t n o t e c Tor t h e first f l u o r i n a t o r i n t h e same r e g i o n .

Two rea::;ons are

proposed f o r t h e h i g h e r sal-t-phase losses 5.n t h e secoild. T l u o r i n a t o r .

First,

t h e fl-i2orid.e s a l t b a t h s i n c o n t a c t with t h e lower regi.ons of t h e second fl.iiorj.nator contained uran.i.urfl â&#x201A;Źor a p e r i o d approx

f i r s t Yluorinator. UElIlil.Jiil

67% I.o:nger

than f o r the

A s w i 1 . l be described i n a latier seeti-on, -the presencc of

i n .PilSed fluoYiiie s a l t systems d u r i n g bench- s c a l e v o l a t i1.i ty cor-

r o s i o n s t u d i e s has en'nanced cor?-osive a t t a c k .

Secona, al~Lho-~~gh t h e to-La1

yirarrtity of f l u o r i n e sparged during M a r k TT was on1.y sl.i.ghtly higiier t h a n tha1; used during o p e r a t i o n s wi.Lh t h e Mark I vpssel, t h e to'cal t : h e of i"1uorin a t i o n f o r t h e Mayk I1 vessel w a s approx 50'11,l o n g e r than f o r t h e f i r s t fluorinator.

Since

iii

b o t h c a s e s an average of

3:l. excess f l u o r i n e over

that


q u a n t i t y necessary -Cor theore-Lieal. r e a c t i o n was used, fLuoririe probably had

o p p o r t u n i t y t o remain i.n t h e salt longer duri.ng Maxk I1 o p e r a t i o n s ,

This

would all-ow t h e c o r r o d e n t a l o n g e r period o f .tI.me t o a t t a c k 'the Tluo.r.iaator Wa1.l..

2.

1 n t e r i . o r Tntergranular PenetraLion Upon e t c h i n g s m p k s removed from t h e w a l l o f t h e Mark I1 f l x o r i -

n a t o r , the grai.si bouriclaries appear h e a v i l y darkened t o vari.ous depths. t h e vapor region, a maximum depth of

s a l t iriterface r e g i o n showed

; I

8mils

p e n e t r a t i o n w a s noted.

In

The vapor-

maximum of 16 m i l s whrile t h e s a l t r e g i o n d i s -

played p e n e t r a t i o n proceedring t o a rnaximim depth of 33

n1iJ.s.

Suspecting t h a t the i n t e r g r a n u l a r a t t a x k might be t h e r e s u l t o f

s u l r u r contamination, personnel a t BMI attempted -t;:m t e s t s t o make p o s i t i v e i d e n t i f i c a t i o n 01-{;begrain-boundary d e p o s i t s .

The sulfitilr-print technicpie,

whereby a c i d i f i e d photographic paper i s pressed a g a i n s t t h e metal. s u r f a c e ,

was used.

Sulfides could n o t be d e t e c t e d u s i n g this method..

Next, t h e re-

action of a s o l u t i o n of l e a d nI-Lrate and n i t r i c acid 11.pon constitu.ent;s a t t h e g r a i n boundari-es w a s observed uncle-r t h e microscope.

Tibe p r e c i p i t a t e

formed appeared t o be similar t o b u t weaker t h a n t h a t observed on a n i c k e l tube known t o be grossly contaminated w i t h s u l f i i r .

R a t t e l l e Memorial I n s t i t u t e

a l s o i n d i c a t e d t h a t the s-Lmctures observed a t t h e g r a i n boundaries resemble t h o s e found in L, n i c k e l rods t e s t e d and sixdj.ed a t ORm.

14-2

A s;ec-t,ion from t h e Mask 11 f l u o r i n a t o r w a l l . which liad been cx-

posed t o t h e s a l t phase was analyzed f o r su.lf11-r c o n t e n t a-t s e v e r a l depths

by &VI personnel,

(F7.g.

24).

Twice t h e weight p e r c e n t of aulYux was round

i n t h e i n t e r i o r w a l l a% a n 0 to ?-mil dep-t;h 80 t h a t found a t t h e same slep.i;ii

on t h e e x t e r i o r w a l l , 2bO vs I20 ppm.

SulTiir a n a l y s e s conducted a t ORNL on

wall m a t e r i a l removed. from various depths i n t h e middle vapor yegioii of t h e

vessel ( F i g . 16) did not disclose any i n c r e a s e in sul.Pim c o n t e n t on subsurface i n t e r i o r samples when compared to subsurface e x t e r i o r samples, 20 vs )-LOppm. Unfortunately, t h e poor correl.ati.on o b t a i n e d on. sul3n: a n a l y s e s

from BMT and ORNL on e x t e r i o r w a l l samples p l u s t h e weak case -for sul.fu-r

4.2

L. R. T r o t t e r m d E. E . Xoffmaiz, P r o g r e s s Report on Volal;il.i.ty P i l o t Plank Cormsion Problems t o A p r j . 1 21, 1957, 01:?&-2hg5, p p 22, 26, 29 (September 30, 1958) 1

e


contamination presented by o t h e r t e s t methods d i l u t e s a n y blarih:t

sialcment

rrhich could be made r e g a r d i n g t h e r o l e t h a t ~ i ~ l f playpd ur i n the i n t e r i o r i n t e r g r a n u l a r a t t a c k o f ihe M n ~ k11 f l u o r i n a t o r - .

However, t h e seri 011s

erlibrittlilig a n 3 p o t e n t i 21 roi-rosi ve e l f f e r t s of s u l f u r i n c o n t a c t w i t h n i c k e l

a t h i g h temperatures arc d e f i n i t e a u d known facts.

Thcrefure,

s u l f u r con-

tamination should be s t i - i n z t a t l ; , avoidpd i n a n ) or tn? W P i s n i c k e l p r o c e s s e qu 7 pljient

.

3.

E x t e r i (xI n t e....r._ g r a.... n u l a r Attack I-

The e x t e r i o r of t h e Mark I T f l u o r i n a t o r s h e l l a l s o underwent i n i e r g r a n u l a r aiiack.

This wab m i e d b y BMl personnel i n iheir examination " h e genepal depth 01 t h e a t t a c k , 1

of samfipler, remuved from til? v e s s e l ,

h

filils,

was o f t h e same o r d e r as t h a t r e p o r t e d â&#x201A;Źor t h e f i r s t VPP f l u o r i n a t i o n vessel.

Tn t h e nnalyscs o f s c a l p frorr tne e x t e r i o r w a l L o f

Mark T I , Hi0

was 2 rou~iili n d i c a t i n t i hal, tlic e x t e r i o r i n t e r g r a n u l a r attac-k o n t h e second 11uor-iLIE

n a t o r w a s due to ail o x i d a t i o n . )I.

Grain-Size Vari-ations Grain sj;es

found i n samples removed From the wall OC tnc Mark J

f l u o r i n a t o r v:_iried fYom an dverSEp MTM number of

5-6

to

o c n i r r e d exclusive13 i n h e vapor r e g i o n of ilie v e s s e l . f l u o r i n a 1 , o r showed a dj f f e r e n t t y a i n - s i

nuidwrs i n t h i s v e s s e l v a r i e d from

ZP

3-5 t o

salt region-

pattern,

2

1. The larse s i z e s

The second VPP

Average AS'IM L r a i i l - s i L e

t h c lsrgest occurriflg jn t h c

Althougn t h e second f l u o r i n a t o r vas â&#x201A;Źabt i c a t p d from tnt: s a w lieat of L n i c k e l and i n a s i m i l a r m a ?

cond t i o n s were q u i t e d i " f e r e n t *

ir?

r a s t h e Yirst vessel, i n i t i a l thermal

the r e s p e c t i v e vafi,or r e k i O M .

Initial

henlvp f o r t h c Mark J w a s done without t h e b e n e f i t o f a n external h e a t source i n t l i u vapor r e g i o n whilc LIE Mark IT had rod-type h e a t i n g elements w i t h a

t o t a l r a t i n g o f 9 kw a t t a c h e 6 t o t h e upper half of t o e v e s s e l .

,+cavy r e -

Trac t o r y i n s u l a t i o n coverpr? tile rod-type elemenLs.

From a c l a s s j c a l net tal h r g i cal vi eqpo i [it, i t , appears t h a t rnany

more nucleaLion s i t e s were p r e s e n i i n t h e vapor r e g i o n o f t h e second f l u o r i n a t o


- 71 as t h e r e s u l t o f the i n i t i a l r a p i d heatup and more o r l e s s incomplete recovery when compared w-i-th t h e â&#x201A;Ź i r s t vessel.

The many s i t e s a f f e c t e d . t h e

p r o d u c t i o n of many grai.ns i n c o n s t a n t voliume which could o n l y r e s u l t i n

COD

p a r a t i v e l y smaller g r a i n sizes.

The somewhat l a r g e r g r a i n s i z e s found i n t h e s a l t region o f t h e

Mark I T f l u o r i n a t o r Itflen compared t o -&,hesame r e g i o n of' t h e f i r s t v e s s e l s i l d t o tlie r e s u l t i n g gm3i.n s i z e s noted i n . the vapor r e g i o n of t h e Mark I1 seen!

t o be -Line r e s u l t ; of some coalescence d u r i n g o p e r a t i o n s . ti).at t h e f i r s t f l u o r i n a t o r was a t

600-725"~for

1-1;w i l l be r e c a l l e d

approx 1250

~

i

while r tile

second v e s s e l 'vas a<; about t h e same bempera'wre :range f o r over l9OO hr.

The s p e c i f i c e f f e c t o f grain size on c o r r o s i o n i n -the f l i i o r i -

m t i o n system h a s been reported I n S e c t i o n I as b e h g c o n j e c t u r a l .

However,

inaximum bi1l.k losses on t h e w a l l s of b o t h f l u o r i n a t o r s occurred a;t l o c a t i o n s

where t h e largest gra-in s i z e s predorntnated.

A s such, the p r o d u c t i o n a n d

s t a b i l i z a t i o n of small grai.n s i z e s i n nickel fluorri.ntition v e s s e l s seem

reasonable p r e c a u t i o n .

a

Open a n n e s l l n g c y c l e s :Tor L n i c k e l t o e m u r e small

g r a i n s i z e s have been r e p o r t e d . 43

E.

Corrosion -of In-ternal Components from--t h e Mark I1 WP F l u o r i n a t o r S e v e r a l i n t e r n a l components of t h e Mai-k I1 f l u o r i r i a t o r have been

zxaimi.ned and a n e v a l u a t i o n ol" t h e c o r r o s l v e attack on t h e s e p a r t s made by personnel of the Corrosion Research Division, BMI. (re-f

44)

Fi.gure 3 shows t h e

l o c a t i o n oii most of t h e s e componenLs w i t h r e s p e c t t o t h e t o p f l a n g e of the fluorina1;or.

01"p a r t i c u l a r i n t e r e s t are t h e d r a f t t u b e s and I"luorine i n l e t

'cubes which, by v i r t u e o f t k i r p o s i t i o n i n t h e system, weye s u b j e c t c d t o

i n i t i a l c o n t a c t by f l u o r i n e , and could. be ex.pected to s u s t a i n t h e g r e a t e s t ;

corroslve attack.

' I k ~ od r a f t

tubes, Mark ITA and Mark I I B , were used i n t h e

Mark II f l u o r i n a t o r d u r i n g Phase T: and Phase I1 of t h e Pluori..nator's l i f e t i m e , (Table V I ) .

The d r a f t t u b e s were f a b r i c a t e d a t OR?& from A n i c k e l .

Results

431'A1mea1ing of Nj ckel, Monel, and. I n c m P l , " Tech. Bill. T-20, The I n t e r n a t i o n a l Nickel Company, Inc., New York, A p r i l , 1953.

44

L e i t e r Report from I?. W. Fink, B a t t e l l e Menorial I i z s t i t u t e , t o R. P. Milford, ORNL Subcontract No. 988 (October '7, 1959).


of tile examinations of t h e drart tuber, and f l u o r i n e i n l e t l i n e s

;ir”

schemsti-

c a l l y d i s p l a y r d i n F i g s , 25 a n L l 30 and show t h e config%ration details of t h e

assenibl i ? s e Supporting p h o t o m i c r o g r y h s are p r e s e a t e d i n Figs, 31 and 32.

Considerable metal loss w a s f o i i o a on t h e Mark TTA drsft tube, buL

l i t t l e v i s i b l e in-i~rgrariiil a r a t t a c k was noted. &-ai’%

Conversely, the Mark I i R

tube showed l i t t l e dimensional chailgr b u t a r a t h e t- deep i n t e r g r a n u l a r

attack.

The eTchinc c h a r a c t e r i s t i c s and g e n e r a l microscopic appearanct- were

also q i ~ i te d i f f e r e n t .

While t h e Mark I13 Lube etclied mrma1-X~f o r n j c k l

usi ng a n i t r i c - a c e t i c a c i d mixture, tile o t h e r d r a f t tube d i d not, anti it vas n e c e s s a r y f o r EM1 p c r s o m e l t o use an HC1-HN0,

(3:1) C ’ L C ~ , which iliey commonld

3

usc f o r Tnconel t o develop grain-boundary d e t a i 1.. anal-ysis a t I341 showed t h e MW’I

114 n i cke 1

liowever, s p e c t r o g r a p h i c

I I B d r a y ! Lube c o n s t r u c t i o n l n a t e r i a l t o bc A

I

The iiiaxiwm b u l k m e t a l l o s s on the Mar.:..

I T A draf:, l u b e bj, micrometer

average measurement w a s 77 m i l s and oecurFP,l n e a r the upper support p l a t e o f t h e assembly.

Compai-ison o f the measured o u t s i d e aiamctcr of ihe L u h ~with

t h e o r i g i n a l dialnrter i n d i c a t e d t h a t most of t h e metal- l o s s occurred o n tiie

o u t e r s u r f a c e s o f t h e uni t.

Microme i ~ iriea’;lireiiienLs r on Uie Mark TTB draft.

tube showed m a x i m i m bulk l o s s e s of on13

6 mils

’OUZ a rnaxirlium total i n t e r -

ic,ranular p c n e t r a t i o n on b o t h t h e i i i t r r i o r and e x t e r i o r w a l l o f 29 mils.

Tne

f l u o r i r i e i n l e t lines a s s o c i a t e d w i t h t h e Mark TTB d r a f t tube ass-mbly showed s i m i l a r c o r r o s i v e behavior when coiiipared i o ihe d r a f t tube b o d i e s .

However,

ilie Mark ILA f h o r i n e i n l e t l i n e showed a much more severe intPr5rariiilar a t -

t a c k on t h e i n s i d e of ilie pipe when compared w i t h t h e o u t s j d e .

A high-probe l i n e and a thermocouple w e l l , b o t h mad:. Prom

3/&?-in.

sched-ilo A n i c k e l , were i n s p e c t e d a l s o by €341 personnel for c o r r o s i v e a t t a c k .

Both components opernLed a t temperatures s s s e n t , i a l l y t h e same a s thos;c. of tile I”luorinat,or w a l l .

The high-probe l i n e w a s a high-pressure l i q u i d l e v e l and

density-pl-obe combination which exienr?ed Y r o m t h e t o p f l a n g e of t h e f l u o r i n a t o r beneaih t h e molten s a l t l e v e l .

The l i n e ~wa:; open at, ille boiiorn to

a l l ow c o n t a c t w i t h t h e f u s e d Lluoride salt baths, b u t p-essuri zed n i t r o g e n ,

i n s i d e t h e tubp, f o r t h e most p a r t prevented t h e s a l t s froiii e n t e r i n 2 tile t u b e ,


-

73 Unclass i f i e d M I A32545 840 mils1

I------

I

21 A

m-rnils thickness (average by micrometer)

Scale: Approximately 1/2 size

Fig. ?9. Corrosion Losses on t k Mark IU.Draft Tube and Fluorine Inlet from the Mark II WP F l u o r i c a t o r . Considerable metal l o s s has o c c u r r e d at all areas b u t most of the intergranularly attacked grains appear to have sloughed oPS.


Unclassified ,

EM1 C q y

Unc lassifie d

Brn c.574

d

a

,

Unclassified z3MJ

c673

Uncles s ified EM1 C672

9

'

I i

Fig. 31. M i c r o s t r u c t u r e s of Samples from A Nickel Draft 'Tubes Used (a) and (b) e x t e r i o r and i n t e r i o r s u r f a c e s i n Mark I1 WP F l u a r i n a t o r . of Mark I I A d r a f t tube at S e c t i o n 2LB; ( c ) and (d) e x t e r i o r and i n t e r i o r surfaces of Mark IIB draft tube a t S e c t i o n 11F. Etchants: (a) and ( b ) H y d r o c u o r i c - n i t r i c a c i d , ( e ) and (a) N i t r i c - a c e t i c a c i d . ~ O O X .


-

76 -

UnclassifLed BMT c676

"

I

. .

(a)

Unclass f r i e d Unclas s i fiea BMI e677 BMI c678

..

. .

. , * '

. I

. 4 *

. I

..

Fig. 32. Microstructures of Cross S e c t i o n s 3Thraugh A N l c k e l FluorPne I n l e t Tubes from (a) Mark IIA Draft Tube (b) Mark IIB Draft Tube. Etchants: N i t r i c - a c e t i c a c i d , 7OX.


- 77 Tl1.e the-mocouple w e l l was p o s i t i o n e d i n a si.niilar manner t o t h a t d e s c r i b e d

for - h e probe li.ne b u t t h e end w a s s e a l e d w i - L h an A n i c k e l p l u g -

Table X

ci.tes t h e c o r r o s i v e losses foiiizd on t h e high-probe l i n e and t h e n o w e l l as

w e l l as g i v i n g mom d e t a i l on t h e l o s s e s found 3.n t h e f l u o r i n e i n l e t l i n e s .

The i n t e r n a l components from t h e Mark I1 VPP f l u o r i n a t o r s u s t a i n e d

total c o r r o s i o n losses comparable .to t h e wal.ls of t h e f l u o r i n a t Z o n v e s s e l .

No i n c r e a s e d a t t a c k was noted on t h e f l u o r i n e i n l e t l i n e s or on the d r a f t

tube liodies as the result of t h e proximity t o e l e m e n t a l fluorine during operations.

Of i n t e r e s t i s t h e indi c a t i o n of rrruch more corros:i.ve c o n d i t i o n s p r e s e n t d u r i n g t h e L-L through L-4 rmns when compared t o

L-5

through L-9 rums.

E-3 through E-6 or

Extended times 0% s e r v i c e a t high -temperatures for

t h e early "L" runs may ex@a.in t h e s e d i f f e r e n c e s .

Corrosion control. s p e c i -

mens of L n i c k e l i.np l a c e during the run groups mentioned, an.d r e p o r t e d i n S e c t i o n TV,

c o r r o b o r a t e th.e v a r i a b l e corrosive behavior p r e s e n t during t h e s e

d i f i"er.er1-t o p e r a t i o n groups.

111. Bench- S c a l e Fluorination Corrosion S.67id-ies The V o l a t i l i t y S t u d i e s Group, Cheni%cal.Development S e c t i o n A o f t h e Chemical Technology Divtsion, has continued t o study p r o c e s s chemistry i n connection w i t h t h e v o l a t t l - f t y process s i n c e t h e i r e a r l y work i n d i c a t e d t h e

l a t t e r ' s fea.sibility.

These s t u d i e s have included t h e g a t h e r i n g of c o r r o s i o n

d a t a from s m a l l - s c a l e experiments.

A s s t a t e d i n Sec-Lion I, nickel-base alloys have shown s u p e r i o r cor-

r o s i o n r e s i s t a n c e t o f u s e d f h o r i . d e s a l t s under dynamic flow c o n d i t i o n s ,

and n i c k e l and. n i c k e l - b a s e a l l o y s e x h i b i t g e n e r a l l y good r e s i s t a n c e t o ele-

mental f l u o r i n e a,nd UFs.

In t h i s connection, corm-ercial purity n i c k e l and

Inconel have been the primary mater-ials of c o n s t r u c t i o n f o r f a c i l i t i e s u s i n g

the i n d i v i d u a l c o r r o d e n t s mentioned above

I

Extensive s t u d i e s a t ORNL on

Inconel i n c o n t a c t w i t h fused f l u o r i d e s a l t s have shown t h . a t a p p r e c i a b l e q u a n t i t i e s of chrornium were renioved through r e a c t i o n

w i t h UF

4 and

other


I

- '(8-

4

mop nl

r--I c? 0 I

L n L n

-3

c\o4

H

r--4

r-0.l

a, P

P

3

a,

H

G

r i

c?Mir)Ln

m ffl

a,


o x i d i z i n g impuriti-es. "c5 T'he chromium removal was accompanied by t h e fomat i o n of subsurface voids i n t h e me-Lal.

S u b s t i t u t i o n s of molybdenum i n an

approximate r a t i o of 2: 1 (MG: C r ) f o r about h a l f of t h e c'm-omium c o n t e n t i n

EL

t y p i c a l chromium-containine all.oy, p l u s o t h e r modifications, provide an a l l o y , INOE

8 , which has e x h i b i t e d

measurable a t t a c k when i n c o n t a c t with molten

f l u o r i d e s a l t s a t temperatures u.11 t o approx 700째C.

Also, INOR 8 has been used

as tfie m a t e r i a l of c o n s t r u c t i o n for the VPP Dissolver-,Yydrofluorinator, t h e

rn-ajor vessel f o r t h e head-end cycle of t h e V o l a t i l i t y Program. For t h e s e reasons, a 2-in.-diam

Inconel f l u o r i n a t o r ,

A n i c k e l f l u o r i n a t o r s , and f o u r 1-in.-diarn

t e n 1-in. -driam

IN@R 8 f l u o r i n a t o r s were t e s t e d

and. subsequently examined for comparative c o r r o s i o n behavior.

Inconel F l u o r i n a t o r

A.

1.

T e s t Method The Inconel f l u o r i n a t o r w a s used i n h o t - c e l l s t u d i e s and was

f a b r i c a t e d from 0.065-in. Table X I ,

stock a t OXNL.

P r i o r t o t h e exposure d e t a i l e d in

f l u o r i n e flowed i n t o the f l u o r i n a t o r as it w a s r a i s e d from ambient

Table X I .

Exposure Conditions for t h e Inconel F l u o r i n a t o r Vessel

Temperature

,

O

600-800

C

Time of exposure a t temperature, hr w i t h salt molten Thermal c y c l e s Fused s a l t , nominal mole

187

70

$

F l u o r i n e i n p u t , standard IXters

a

a

Uraniu-m i r r a d i a t e d , riot enriched.

45W. D. Manly e t al. , " M e t a l l u r g i c a l Problems i n Molten F l u o r i d e Systems, Progress i n Nuclear Energy, S e r i e s I V , Vol 2 - Technology, Engineering, and Safe ty, p - ~16b--l79, . Pergamon Press, London, 1960.

I'


- 80 room Lerqerature t o operai;.i.f i g temperature.

This was done For leak-.teskirig

piu-poses although, at t h e same t i m e , t h e in-teu.:ioi" v e s s e l walls w e i ~pi-obably "conditionedr' by prod-ucing f i l m s OF fliiori.d.es.

The to-tal.Lime -involved for

t h i s t e c t i . n f f - c o n d i t i o n i n ~i,.rea~l;mentw a s abou-t 2 hr.

A f t e r exposure o p e r a t i o n s , areas from the v e s s e l were se7.ected f o r

micrometer measiri*ements and metallograp,iiic examination.

c r o s s s e c t i o n o f the v e s s e l aj.id t h e l o c a t i o n o f stirdy.

Figure 33 shows a

ti^ sample a r e a s remcved f o r

A summary of c o r r o s i v e a t t a c k found i s shown i n Table

XI1 ishere total.

l o s s e s a r c repor-Led i n imi.1~pcr hour, based on fl.uorine sparge .Lime, and m i l s

p e r mon-Lh, based on residence -Lime in mo3.ten salts. mi c r n g a p h s are grouped i n Fi.g.

2.

$.

R e p r e s e n t a t i v e photo-

Discussion of R e s u l t s Maxi.inuii: c o r r o s i v e a-I;Lack i n t h e Tnconel f l u o r i n a t o r vas encoun-

tered. a t t h e vapor-sal-L i n t e r f a c e and occurred ai; a r a t e or 0.2lt mils/hr,

based

on PluorLnc spsrge -time, o r 118 mils/noni;ii, based. on molten- s a l t r e s i d e n c e t i . m e . I n t e r g r a n u l a r penetration seemed -the predoniiriaat nodc OP at'iack i n tiie salt

and vapoi- refilms b u t no evidence of i ~ n t e r g r a n u l a rcorros:ion was found a t tiie

vapor- s a l t i n t e r f a c e

In t h i s connection, -ihe i n t e r g r a m l a r - p,e1lctiVatioi? seemed d i s -

simri.I.ar t o t h a t fourid on t h e i n t e r i o r w a l - l s oT -the WP f1uori.nators.

on t h e Inconel. v e s s e l t h e r c

WRS

'That i.s,

evidence o f t h e sloughing of whobe g r a i n s of

materi.al_, a c o n d i t i o n noi; observed. on t h e â&#x201A;Ź u l l - s i z e L r-rickel. v e s s e l s .

ilhe

depth o f t h e interg.canu.lal- p e n e t r a t i o n on t h e Ihconel vessel was 0nl.y a single grab deep:,, The VYP f l u o r i n a t o r s d-emonstratedi.ntergranii,lar rnodj.fi.cations

many gralms i.n d e p t h on samyl.or, removed from corresponding s e r v i c e regions cont a i ni.ng s i m i l a r pai.n-.si_ze material.

In t h e Inconel bench i"l.uori.nator, it appears k h a t a f t e r i n t e r -

graniLLar penetrati-on had proceeded t o abowt o m g r a i n i n depth, many o f the a f f e c t e d grains could not be retained i_n p o s i t i o n by the remainder of t h e

grain-boundary material aiid sloughed o f f , l e a v i n g new mater-jal ready for corrosive attack.

Thi.s method of r e - t a l l o s s woii1.d seem devasLating t o t h e v e s s e l


- 81 UNCLASSIFIED

O R N L - L R - D W G 49462

-0.065-in. WAL THICKNESS

SPECIMEN

F L U0 R 1 NAT0 R

Fig.

33.

Fluorinator.

_. .....-.

Cross Section of t h e Chemical Cevelopolent Section A Inconel Metallographic specimcns TETE: rcmoved a s shown.


Table X I T .

Sumary of Maxirrm Corrosion Results on Chemical Develo3trient Irx o ne 1 F l ~;roicator ._

Speci-

nen

Estimate2 Wall Speciner; TeKp

Location

No.

( O C >

Wall

T h i ckne s s Loss

(miisla

250

500

3 3 8

2 vapor- s a i t

600-Soo

12

1

600-800

9

12 top vapor LO q p e r vspor L lower vapor in-krface S&lt

I

100

intergrsmlm Pe ne t re-ti OK. Interlor Ex-teri o r

To4Gai

Corrosion

3

2

5 -

li

24b

2

-

il

44

(KiiSj

-

3

(rnlls)

(ails)

10

F~

a ~ o - nmcrorr,eter measdrernents -Laker, i n eac'i srea.

b

Losses Converted t o Nils ';.nit ?$me xils/xonth n i l s / h r (mol-ten- (F2 s9arg.n sa12 time) tiixe)

wall

-$a11

Does not inclLide tae e x t e r i o r a t t a c k _'ound on 'che v e s s e l w a l l .

'E

Y2

0.36

40

0.12 0.20

0.22

I


-

Y-26551

83

-

UNCLASSIFIED 0 RN L- LR DWG 32069

-

Y-26548

6 t

INNER SURFACE, VAPOR AREA

**-

4 OUTER SURFACE-, VAPOR AREA

Y-26549

h

,NNER SIJRFAC:E, APPROX. SALT-VAPOR I N T E R FA C, E t

I N N E R SURFACE, SALT AREA

Fig. 34. Typical MicrostructlJres of Samples Removed Trorii Chemical Development Inconel Fluorinator. Etchant: Glyceria regia. 250X. Reduced 3276.


i n s e r v i c e , b u t t h e anoma1.y o f t h e s i t u a t i o n i s t h a t maximin w a l l - t h i c k n e s s l o s s e s occurred i.n t h e Inconel v e s s e l a t t h e v a p o r - s a l t i n t e r f a c e and a t -that p o i n t no evi-dence o f i n t e r g r a n u l a r a t t a c k could be found.

No e x p l a n a t i o n can be given f o r t h e i n t e r i o r w a l l i n t e r f a c e anomaly d e s c r i b e d nor can one be given f o r t h e heavy e x t e r i o r i n t e r g r a n u l a r

a t t a c k which has l o c a l i z e d i n a c o o l e r r e g i o n of t h i s Inconel f l u o r i n a t o r ( s e e ~ i g 34). .

B, A N i c k e l P l u o r i n a t o r s I

1.

T e s t Method. In a d d i t i o n t o t h e Inconel f l u o r i n a t o r r e p o r t e d lipon i n

S e c t i o n ITPA, t e n A n i c k e l m i n i a t u r e f l u o r i n a t i o n ?-essels, each 1 - i n . and 0.035-in.-wall.

-0.d.

ti?i.ck.ness, have been o p e r a t e d by the V o l a t i l i - t y Studi.es

Gi*oup, Chemical Development

Sec-Lion A,

i n o r d e r t o compare f l u o r i n a t o r cor-

r o s i o n u s i n g d i f f e r e n t process f l o w s h e e t s .

Figure 35 shows t h e uniJLs i n t e s - t

p o s i t i o n , while Table X I I T i s a summary of t h e imposed t e s t cofiditions. The v e s s e l s , j.n a l l cases, were charged w i t h 75 g of f l u o y i d e s a l t t h a t had been ground and cl-assified t o

-8 +20 mesh.

The v e s s e l s were

t h e n p l a c e d i n s p l i t ; tube-type Furnaces and.brought t o t h e s p e c i f i e d temperat u r e under a n i t r o g e n purge o f 0.05 l.iters/min.

A-l; temperature, t h e n i t r o g e n

w a s bypassed and f l u o r i n e was allowed t o bubble thiwugh t h e s a l t a t t h e same flow r a t e .

I n iliose c a s e s where urani.um w a s added t o t h e m e l t , 0.50 g

incret-nents of UF

added a t interva1.s o f 1 h r o r more.

4 were

As shown, some

r e a c t o r s were p l a c e d i n s e r i e s b o t h f o r conveni.ence and t o mini-mize t h e f l u o r i n e consumption.

50

The -total. e k r n e n t a l f l u o r i n e exposure i n each case

h r at, a rate of 0.05 I.iters/min.

a c t o r s Nos. 5,

6, and

Du-t.ing t h e s e 50-hr exposures on t e s t re-

10, twenty-five UF

were made.

7.7a-13

4 additions

and Uli'

6 volati.lizati.ons

I n a l l . t e s t s , t h e s a l t s were kept molten f o r over 200 h r while under a n i t r o g e n purge.

This w a s done t o f a c i l i t a t e t h e t e s t procedure, t h a t

i s , a v o i d r e m e l t i n g s a l t s f o r t h e next f l u o r i n e t e s t period. .Figures 36 and 37 i l l u s t r a t e the c o r r o s i o n r e s u l t s o b t a i n e d by rni.crometer measurements and


- a5 -

F2

i

-

--

ratus f o r Comparison of Fluorination Corrosion on A Nickel


Table XIII.

86 -

Process Conditions for A Nickel Bench-Scale Test Fluorinators

Hr of Molten H r of Molten Salt Exposure Salt Exposure Position in Vessel Fluoride Temperature ("C) With N2 Sparging With F2 Sparging Test Series No. Salt

* *

1

4

*

7

* *

8

2

5

9

450 525 525 525 600 600

2 +

0.5% U

**

525 525 600 600

3 + 0.5% U

10

H*

3

6

1 + 0.5% U

*2&37-37

**31-24-45

additions.

-5(j50

mole

%

222

238 240

1

1

1

240

2

238

2

222

240 240 222

238

2

3

1

3

1

LiF-NaF-ZrF4: Composition 31, plus LiF addition.

mole $I LiF-NaF-ZrF4: Composition 31, plus LiF and ZrF4

mole

%

NaJ?-ZrF4:

Composition 31, as received.


I

0 W

+

z

- 0

c

__I

2

-1 v)

I

M N

M

N

J

>-v, 0 0

10

N U

87 -

0

:: s-"

N+?2 0 M

i

,X a 111

+ L

> W

0 0

M

0 0 (0 N

M

M

-

N

M

_-

s-"

0

n+q3 m

W

0

m m

E

<


.........

.........-

- .

,-~.

> - w l

> - v ?

-

0

I n

0

u)

In

W

N + ? 3

In N

N

In

0

N

N

s-”

m

88 .-

> - G I

In N In

m

In

> ... In N

--

v?

e

0

<o+lqI’

2

> - v )

0

cti


- 89 metallographic examinations of specimens removed from t h e v e s s e l s .

The losses

are r e p o r t e d b o t h i n mils p e r hour o f f l u o r i n e sparge and m i l s p e r month based on t o t a l r e s i d e n c e time i n molten s a l t s f o r comparison t r l t h o t h e r s t u d i e s .

F i g u r e s 38 through

42 show r e p r e s e n t a t i v e photomicrographs from t h i s t e s t

series. 2.

Discussion of R e s u l t s The A n i c k e l f l u o r i n a t o r s showed widely varying c o r r o s i o n r a t e s

as a n t i c i p a t e d i n plaruiing t h i s t e s t s e r i e s .

6

Comparison of t h e r e s u l t s on t e s t v e s s e l No.

wit11 those of

v e s s e l No. 3 i n d i c a t e d t h a t uranium a d d i t i o n s t o equimolar NaF-ZrF

4. r e s u l t e d

i n i n c r e a s e d c o r r o s i o n o c c u r r i n g as i n t e r g r a n u l a r a t t a c k a t tl?e vapor- s a l t interface.

A r a t e o:f 0.1 m i l s / *

the i n t e r f a c e of No.

based on f l u o r i n e sparge

6.

Comparison of v e s s e l No. 2 w i t h v e s s e l No.

additi-on of 26 mole

tiine

of

was noted at;

3 indicated t h a t the

LIF caused i n c r e a s e d a t t a c k a t t h e v a p o r - s a l t i n t e r -

face, as evidenced by bulk metal l o s s e s .

Upon metallographic examination, no

evld.ence of i n t e r g r a n u l a r a t t a c k w a s found i n e i t h e r v e s s e l . The a d d i t i o n of u.rani.um t o t h e LiP-NaB'-ZrP4

(26-37-37 mole $)

s a l t i n v e s s e l No. 5 r e s u l t e d i n s i g n i f i c a n t l y i n c r e a s e d metal l o s s e s pliis intergyanular a t t a c k at the vapor-salt interface.

Additional intergranular

a t t a c k w a s noted i n t h e vapor phase of t h i . s v e s s e l . Lowering t h e tempera6ure of t h e r e a c t o r c o n t a i n i n g t h e same LiF-bearing s a l t , LiF-NaF-ZrFI corrosion r e s u l t s .

4

Two of t h e

(26-37-37 mole $1, to v e s s e l s , Nos. 4 and '7,

525째C produced e r r a t i c

showed uniform, compara-

t i v e l y s m a l l . metal. losses i n a l l r e g i o n s while v e s s e l No. 8 showed an i n c r e a s e d a t t a c k , especially a t t h e v a p o r - s a l t interfac!e

e x h i b i t e d by v e s s e l No. 8.

.

Intergranular attack was also

A s shown i n Table X l I 1 , v e s s e l No. 8 w a s i n a down-

stream p o s i t i o n from v e s s e l s N o s .

4 and

'-(, arid t h e d e v i a t i o n i n behavior may,

t h e r e f o r e , have been t h e r e s u l t of carry-over and c o l l e c t i o n of c e r t a i n cons t i t u e n t s conducive t o greeter c o r r o s i v e a t t a c k .

'

"

~


Y - 28366

- 90 -

UWCL 4 S S I F I E D ORNL-LR-DWG 49825

Y - 28369

~-2836 ..........-

...-.

’. I

..

. e

1

Y- 28367

’ .

.

INNER SURFACE,

A P P R O X l M AT E SALT - VAPOR I NT E R FACE

b.

c .-

A N

INNER S U R F A C E , S A L T A R E A


*--


- 92

u r J c L a ~ 5I E1 D~

-

ORNL-LR

3 ' N G 49828

Y - 28639

Y-28366

I

I

.i.

Y-28638

I

/

1.

'

A S R E C F I V F D MATERIAL

INNER S U A F n C E , VAPOR ARFA

f

Y - 28637

~

.........

INNFH SURFACE A P P R O X I M A l - k SAL T - V A P O R INNE HFACE

1 .-c

L

I

N

INNER S U R F A C E . SA1.T A R E A

%st

T y p i c a l Mj crostruc1,iires of Samples rroili A Ni eke1 Minia+,ure 110. r ' l u o r i n a t o r No. 6. E t c h a n t : Acetjc-nitric-hydrochloric a c i d . 200X.

Fig.

I


Y-28366

- 93 -

UNCLASSIFIED ORNL - L R - D W G 49823

.

A S RECEIVED MATERIAL

INNER SURFACE, A P P ROX IM AT E SALT - VA PO H IN T E RFACE

INNER SURFACE, SALT A R E A

F i g . 41, Typical Microstructures of Samples from A Nickel Miniature Test Flu-orinator No. 8. E t c h a n t : Aeetic-rLitr-i.c-hydrocUor1c acta. 2OOX.


- 94 ......

UNCLASSIFIED ORNL-LR-DWG 49830

Y-28613

P 0

f

- 4 +

A S R E C E I V E D MATERIAL

0.

r e

t

J

INNER SURFACE APPROXIMATE SALT-VAPOR IN NF R FACE

INNER SURFACE, S A L T A R E A

F i g . l+P. Ty-plcal Microstructures of Samples from A N i c k e l Miniat,ure T e s t Fluorinator No. 10. Etchant: Acetic-nitric-hydrocilloric a c i d . 200X.

,


- 95 Lowering t h e p r o c e s s temperature t o 450°C and u t i l i z i n g t h e same l i t h i u m - b e a r i n g s a l t (No. 2 ) reduced. c o r r o s i v e a t t a c k t o t h e lowest l e v e l s

found i n t h i s t e s t series.

These results were provided by v e s s e l No. 1 where

t h e approximate losses were 0.02 rnil/hr,

based on f l u o r i n e sparge time.

This

i s es p e c i a l l y si.gni f i c a n t since l i t h i u m - sodium- z irconiurn f l u o r i d e s a l t mix-

, t u r e s can be used i n t h e v o l a t i l i t y process a t lower o p e r a t i n g temperatures

t h a n t h e NaF-ZrF4 composite system because o f the lower l i q u i d u s l i n e of t h e li thium-beari-ng s y s t e r n .

Tes-ts Nos. 10 and

s a l t s , 31--2b-h$ mole

$J

9 at

LiF-NaF-ZrF4,

525°C used h i g h e r LiF- and ZrF4-content

wi.th and without 3-iranium, r e s p e c t i v e l y .

Vessel No. 9 showed s l i g h t l y i n c r e a s e d a t t a c k over v e s s e l s Nos. were o p e r a t e d at t h e same temperature.

4 and

*(‘ which

Metal1ographi.c examination of

v e s s e l No. 10 r e v e a l e d t h a t intergramil.ar p e n e t r a t i o n w a s p r e s e n t i n a l l phases of t h e i n t e r i o r w a l l . The A n i c k e l miniature f l u o r i n a t o r s demonstrated g e n e r a l l y lower r a t e s of corrosi.ve a t t a c k i n simulated f l u o r i n a t i o n environments when compared

t o t h e f u l l - s i z e d L n i c k e l v e s s e l s o r t h e l a t t e r ’ s A ni.cke1 i n t e r n a l components

x&-ich were exposed t o p i l o t p l a n t f l u o r i n a t i o n c o n d i t i o n s .

reasons can probably account f o r most o f t h i s dev-iatton:

The following t h r e e (1)t h e temperatures

of f l u o r j - n a t ?on g e n e r a l l y were somewhat lower i n t h e bench- s c a l e work than diiri-ng p i l o t p l a n t o p e r a t i o n s ;

( 2 ) somewhat b e t t e r c o n t r o l over thermal c y c l i n g

and o t h e r p r o c e s s c o n d i t i o n s w a s o b t a i n e d during bench-scale work; (3) t h e f e e d s a l t s used i n t h e p i l o t p l a n t w o r k were contaminated by having been used

i n previous loop s t u d i e s , the AEE, o r having been contained f o r long p e r i o d s

of time i n t h e p i l o t p l a n t type 347 s t a i n l e s s s t e e l charge melt tank.

The A n i c k e l m i n i a t u r e s a l s o demonstrated g r e a t e r r e s i s t a n c e t o

c o r r o s i v e a t t a c k d u r i n g f l u o r i n a t i o n t h a n t h e I n c o n e l v e s s e l used i n Chemical Development h o t - c e l l s t u d i e s .

C.

INOR-8 P l u o r i n a t o r s 1. T e s t Method Four IN OR-^ t e s t f l u o r l n a t i o n v e s s e l s , e a c h 1-in.-0.d.

0.065-in.-wall

and

thLckness, and of similar d e s i g n t o t h e A n i c k e l r e a c t o r s


- 96 r e p o r t e d i n S e c t i o n IIIB were also f a b r i c a t p d a t ORM, ror bencii-srale

v o l a t i l i t y corrosion s t i i d j e s . n a t o r s wa,,'(4.5 wt

The composi t i o n of 1 N O R - 8 i ~ s e di n test T l u o r i -

$ Ni--15.3 wi $ Mo-6.5

wt

$ CP~.(

rvt

5

FP-0.02wi $ C.

A summary ol" ihe test, c o n d i t i o n s I"or tile IPJOR-8 riiiniatuie I'luo-rinal,c)rs, as shown i n Tab1.e X I V , i n d i c a i e s that 0 ~ 1 sv e s s e l No. 3 contained I s -o l e XTV.

r i

Vessel No.

Flucride Sal i

1

,*

2

Yr of Molten H r o f Molten Ti?mpPratiire Salt Exposure S a l t Exposure Posy-tion i n ("C) With N2 SpargLng With F2 Sparging T e s t S e r i e s

2 + 0*5$ IJ

4

-salt

4jo

2 36

50

h50

290

50 50

2 36

600

.3c)s

3

Process Coiidi t i o n s f o r INOH-8 Azr,ch-Scal e Te st Flu0 r i natai"s

600

3c

*2G3j7--37 mole

$I

1

50

290

2

1

1

-_ .............-

. ..................._

_.__ .

LiF-NaF-%rF4: From a d d i i i o n o f T,iF t o Composiiion 31.

~

**50-50 mole $ NaF-ZrFh:

urar;ium.

Vessel. TTo, 3 received 25 UE'

fLiJorinated t o UF ported.

Compositi.oa

Figs-t-es

6 ili

31, as

4 additions

l 7 . k maimer as t h e

1-ecci.ved.

which were s i i b s e q x n t l y

A n i c k e l miiiiatures p r e v i o u s l y re-

'13 and 44 i l l u s t r a t e t h e c o r r o s i o n losses obtained by microrn-

e t e y measuremenLs and rneta3-lographic examinations on specimens removed Tron

the wz~l.2.s of t h e vessel.

The l o s s e s have been converted io mils I s s t p e r

uni-i; tiiiie fol- compari.son purposes,

F i p p r e s '15 -tiwough

48 show

t y j ? i c a l etched

m i c r o s t r u c t u r e s found i n the INOR-8f l u o r i l i a t o r speci-mens. Discussion of 3 e s u l t s

The SNOR-.~ test T l u o r i n a t o r s showed a vari et) o P c o r r o s i o n

f e s t a l , 7 011s depending on t h e t e s t c o n d i t i o n s .

operated a t

6oo0c,

)+,

-

Consideriiig t h e t w o v e s s e l s w h i c h

vessel N o . ?, which c o n t a i n e d eqiiirnolar Na3-ZrF

less attac.1.c than v e s s e l N o .

inanj

)I'

which coniajiied LiF-NaF-ZrF), (26-37-37

showed

mole $I).


X

s'

Q

0 cf


01

N

IC)

0

L?

N t < 3

I

221

N

- 98 -

I

_..-

t

m

r: 0

F: 0

cn

?-I

k k

0

0

u

0

k


Y - 28800

-

99

-

UNCLASSIFIED O R M L - L R - DWG 49831

Y-2880'

Y - 29062

A S R E C E I V E D MATERIAL

Y-28803

f

Fig. 45. Typical Microstructures of Samples f r o m INOl3-8 Miniature T e s t Fluorinator No. 1. Etchant: Modified aqua regia. 200X.


- 100

Y-28801

s

UNCLASSIFIEC ORNL-LR-DWG 4 9 8 3 2

I

Y - 2906 2

.

,

I

!

i

;t I

I

I

\

AS RECEIVED MATERIAL

.

I

'I 1

I

,

.,

e--

).

I

I 1

.

1

*'

I

ll_l

SALT AREA

Fig. 46. Typical Mi-crostructures of Samples f'roin INOH-8 Miniature T e s t Fluorinator No. 2 E t c h a n t : Modified aqua regia, 20OX.

I


-

101

-

...._ -.

Y-28851 ______

._. .....

UNCLASSIFIED O R N L - L R - D W G 49833

Y-29062

I

t

I !

B

A S RECEIVED MATERIAL

Fig.

47.

Typical M l c r o s t i ~ @ t u r rof s Sampl-es f r o m ex0~.-8Miniature T e s t Etchasll;: Modified aqua r e g i a , 2OOX.

Fluorinator No. 3.


UNCLASSIFIED

O R N L - L R - DWG ese 3 4 ___..... Y- 591362

.-

- - --+

m___

MIDDLE VAPOR ARE&

J

AS RECEIVED klATERIAI. ...

~ i g .48. Typical Mierostruct;ures of ~ a m p l e sfrom ENOX-F) Fluoranator No. 14. Etchant: Modiffed aqua regia. 2OOX.

Miniature est

c


-

103

-

Maximum a t t a c k i n t h e l a t t e r v e s s e l o c c u r r e d a t t h e v a p o r - s a l t i n t e r f a c e a t

a rate of 30 mils/month,

based on r e s i d e n c e time i n t h e molten s a l t s .

was t h e max.imum a t t a c k r a t e f o r tine e n t i r e INOR-8 s e r i e s .

This

Reducing t h e o p e r a t i n g temperature t o 450째C and u s i n g the same

1ithium-bear.ing s a l t s i g n i f i c a n t l y reduced a t t a c k a s i n d i c a t e d f o r vessel. No. 1

43 and 44).

(Figs.

The maximum a t t a c k found i n t h i s v e s s e l was also a t t h e

5

v a p o r - s a l t i n t e r . f a c e a t a r a t e of

mils/month.

The a d d i t i o n of uranium t o

t h e l i t h i u m - b e a r i n g s a l t d e s c r i b e d p l u s o p e r a t i o n a t lt5O" C more t h a n doubled

the c o r r o s i v e a t t a c k when compared t o t h e nonuraniurn-containing s a l t .

This

3.

o c c u r r e d i n v e s s e l No.

Examination of t h e m e t a l l o g r a p h i c specimens i n t h e a s - p o l i s h e d

s t a t e , F i g . 49, d i s c l o s e d spongy l a y e r s on t h e s u r f a c e s of t h e vapor r e g i o n specimens from - v e s s e l s Ros. 2 and

t e m p e r a t u r e s of t h e t e s t seri.es. s o l u t i o n , 5:1, lIC1:EFNO

Figures

46

and

3,

4.

These .two v e s s e l s o p e r a t e d a t t h e h i g h e s t

Upon e t c h i n g w i t h a modified aqua r e g i a

t h e spongy r e g i o n s were f o r t h e most p a r t destroyed.

49 d i s p l a y t h e m i c r o s t r u c t u r e s f o r specimens from

the two

ves-

sels and show Yhat i n on.ly one region, the upper vapor a r e a o f v e s s e l No. 2 (Fig.

46) d i d

s i g n i - f i c a n t 8mounl;s of t h e spongy r e g i o n remain. C a r e f u l r e p o l i s h i n g on the upper vapor area s m p l e from v e s s e l

110. 2 and examination of t h e su.rface d i s c l o s e d a c o r r o s i o n product whj.ch r e -

s o l v e d i t s e l f i n t o t w o d i s t i n c t l a y e r s , as shown i n Fig. 50.

J u s t above t h e

INOR-8 b a s e metal was a spongy r e g i o n wh.ich w a s composed of voids and s o l i d

m e t a l intermixed.

Many of t h e voids appeared to be p a r t i a l l y f i l l e d w i t h

nonmetallic-appearing compounds.

Above t h e spongy region, on the outermost

s u r f a c e of t h e specimen, was an irregular l a y e r t h a t had t h e angular appear-

ance of m e t a l c r y s t a l s .

Upon e t c h i n g t h e specimen w i t h a mixture of lo$

lO$ (m4)2SeOp,,

XCB arid

1:1 r a t i o i n water, t h e outermost l a y e r of t h e s u r f a c e showed

d i f f e r e n t c h a r a c t e r i s t i c s -Liian t h e INOR-8base metal.

The comparatively m i l d .

e t c h a n t d e l i n e a t e d g r a i n boundaries i n the o u t e r l a y e r bu.t left t h e base metal

u n a f f e c t e d , as d i s p l a y e d i n Fig.

51.


- 104

.... .

-

-

F i g . "9. Typical. Spongy Surface Layers f r o m Vapor Region Samples of (a) IIIOR-~ T e s t F l u o r i n a t o r No. 2 (b) INOR-8 T e s t P l u o r i n a t u r No. 4. As-po3.i s h e d . 5OOX.


-

105

-

F i g . 50. Surface Layers on Sample from Vapor Region af INOH-8 Miniature Test Fluorinator No. 2. As-polished. TOOX.


-

3-06

-

Fig. 51. Surface Layers on Sample f r o m Vapor Region of I N O R - 8 Miniature T e s t Fluorinator No. 2 - E t c h a n t : Potassium cyanide-ammonium persulfate. 500x.


- 107 Samples of t h e o u t e r c o r r o s i o n product l a y e r and o r the spongy

su'rJsurf'ace r e g i o n were obtained by mechanical m i l l i n g and scr.appi.ng.

Most

of the m a t e r i a l comprising t'ne o u t e r l a y e r was fouixl t o 'tie s t r o n g l y f e r r o magieLic in contra&

These samples plus mi.lli.ngs removed

t o the base metal,

from the e x t e r i o r diameter of the No. 2 vessel w a l l , p l 0 mils below the

surface, were sinbm.i.tted.f o r spectrochemical analyses. A l l o f t h e samples

were q l l a n t i t a t i v e l y analyzed .Tor C r , Mo, Fe, and Ni by emission spectroscopy usi-ng a porous cup e1ectrod.e -method of sample exci.ta-Lion. s h o m i n Table XV.

The r e s u l t s a r e

Tdble XV. Analyses of Corrosion Produc-t:; and B a s e Metal Removed from IEJOR-8 Miniature F h m r i n . a t o r No. 2

Sample D e s c r i p t i o n and

Chromium

(d$4

Location

Outer c o r r o s i o n product l a y e r

3.9

Spongy subsurface l a y e r

7.6

Base m e t a l

6.6

I _

Iron (th

4)

3.3 3.8 3 '95

Molybdenum

(wt

$7)

8.4 16.3 15.h5

Nickel (7-J-t

$1

84.3 69.It

75.45

Examination of Table XV shows 'chat t h e o u t e r c o r r o s i o n product

layer w a s 13 w t

$I

r f c h e r i n n i c k e l when coinpared t o the base metal, INOR-8,

while the chromium, molybd.eiiim, and iron c o n t e n t s i n the c o r r o s i o n product decreased

40, 45, and

11 Wt,

$,

respectively.

The spongy suhs-urface layer

showed. generally s m a l l weight p e r c e n t h e r e a s e s Tor the ch.romi.um, molybdenum,

and iron, r e s p e c t i v e l y , when compared t o the base m e t a l a n a l y s i s " the subsurface l a y e r was approx 8 w t

%

Nickel i n

Less .than that fou.nd i.n t h e base metal.

The mode of c o r r o s i v e a.ti;aclc on INOR-8 i n c o n t a c t with t h e

sirmiula-Led v o l a t , i . l i t y process f l u o r i n a t i o n envirorment a i 6 0 0 appears ~~ to involve s e l e c t i v e l o s s e s of chromium, molybdenum, and i r o n from t h e n i c k e l s o l i d solution.

This may- oeci1r by formation of metal f l u o r i d e s on t h e b u l k

m e t a l siurface wIii.c?n subsequently v o l a t i l i z e , o r by t h e v a r i o u s retihods of Tluoride f i l m losses d e s c r i b e d i n S e c t i o n I.


- 108 T'he r e a s o n ( s) f o r the s l i g h t l y h i g h e r minor element coricentxat i o n s i n tiie spongy subsurface c o r r o s i o n l a y e r when compared w i t h t h e base

m e t a l a p p e a r ( s ) anomalous t o normal d i f f u s i o n p r o c e s s e s .

Concentratiori

gradi.ents produced by t h e i n i t i a l . s e l e c t i v e l o s s e s should become t h e driv-ing f o r c e For d i f f u s i o n of t h e mTnor alloy elements toward t h e exposed s u r f a c e

ol" t h e r e a c t o r and lower t h a n base metal c o n c e n t r a t i o n s of chromium,

molybdenum, and i r o n would be expected i n t h e subsurface region.

It may be

t h a t complex fluoride compounds aye formed i n t h e subsurface r e g i o n which do

n o t v o l a - t i l i z e under t h e t e s t co-nd~iti.onsand t h u s simply t i e up h i g h e r conc e n t r a t i o n s of chromi-um, molybdenum, and i r o n .

However, s i n c e x-ray

d i f f r a c t i o n p a t t e r n s on samples from t h e subhayer d i s c l o s e d only t h e presence of a f a c e - c e n t e r e d cubic material v e r y s i m i l a r t o tiie p a t t e r i i o b t a i n e d on t h e base metal-, s u p p o r t i n g evidence f o r t h i s t h e o r y has not been o b t a i n e d .

D e t a i l e d txeatment of t h e c o r r o s i v e a t t a c k on INOR-8deserves

s e p a r a t e s t u d y which may o r may n o t be m r r a n t e d conside1-ing t h e u l t i m a t e goal. of t h e e n t i r e t e s t s e r i e s covered

iii

t h i s s e c t i o n ; t h a t i.s, comparative

behavior of A n i c k e l , Inconel, and INOR-8i n c o n t a c t w i t h a v o l a t i . l l t y p r o c e s s f l u o r i n a t i o n environnient.

I n r e g a r d t o t h e l a t t e r , A n i c k e l had t h e b e a t

r e s i - s t a n c e t o a t t a c k a t p i l o t p l a n t i"1uorination temperatures of 600"~; but a t lL50"C INOR-8 p r e s e n t e d f a v o r a b l e competiLion t o t h e ilickel.

There are

s e v e r a l advantages a t t e n d a n t to u s i n g INOR-8 as a f l u o r i - n a t o r c o n s t r u c t i o n

m a t e r i a l i n c l u d i n g i t s h i g h s t r e n g t h and o x i d a t i o n r e s i s t a n c e .

Also,

since

t h e c o n s t m e t i o n material f o r t h e VPP h y d r o f l u o r i n a t o r i s TNOR-8, it might be p o s s i b l e t o c o n s o l i d a t e b o t h h y d r o f l u o r i n a t i o n and f l u o r i n a t i o n o p e r a t i o n s i n

a si-ngle v e s s e l . IV.

V o l a t i l i t y P i l o t P l a n t Scouting Corrosion Tests A.

Material Selection I n order. t o t a k e advanta,ge o f t h e s e r v i c e c o n d i t i o n s provided by t h e

VPP p r o c e s s runs

an;l t o achieve i n s i g h t i n t o t h e r e s i s t a n c e of o t h e r m a k r i a l s

t o tiie complex f l u o r i n a t i o n rnviropment, a s e r i e s of c o r r o s i o n specimens w a s l o c a t e d i n t h e Mark 1 and Mark T C f l u o r i n a t o r s l asld examined a t convenient


- 109 irrtervals.

As mentioned i n S e c t i o n 1, resistianee t o f u r t h e r attack by

f l u o r i n e on metals w a s felt t o be imparted by p a s s i v e f l u o r i d e -r"ilmswhich

form on t h e me-tal.

P r o t e c t i o n 1rs.s been shown. t o be dependen'i;

011

the proper-

t i e s of' t h e f l u o r i d e Y i l m s , e s p e c i a l l y v o l a t i l i t y , adherence t o t h e s u b s t r a t e

metal, mechanical and the.rrm.1 s t a b i l i t y , and t h i c k n e s s

For t h e s c o u t i n g c o r r o s i o n t e s t s d.escri.bed i n t h i s sec.tioa, selec-

t i o n of m a t e r i - n l s which contained c o n s t i t u e n t s known t o Porm low vol.ati1.e f l u o r i d e s seemed e s p e c i a l l y a p p r o p r i a t e .

A s a g 1 i d . e to v o l a t i l i t y , tile

m e l t i n g and b o i l i n g p o i n t s of t h e common i n g r e d i e n t s j.rt many commercfal

m a t e r i a l s o f c o n s t r u c t i o n were reviewed. i s shown i n Table X U .

146

A partj-al. l i s t l n g taken from Brewer

It can be seen t h a t chromium and molybileiium, commoo1.y

added f o r improved r e s i s t a n c e t o a i s o x i d a t i o n and/or iriiprovemcnt, of higbtemperature p r o p e r t i e s , form h i g h l y v o l a t i l e Fluorides, e s p e c i a l l y a t t h e i r higher oxidation s t a t e s .

Nevertheless, because of t h e previous use of n i c k e l -

base a l l o y s c o n t a i n i n g chromi-um ( I n c o n e l ) and/or mo1ybdenu.m (INOH-8) i n

the A i r c r a f t I'ieactor Experiment (ARE) and t h e Molten-Salt Reactor ( P E R ) studi-es,

a l l o y s c o n t a t n i n g t h e s e t w o c o n s t i t u e n t s were included i n t h e materials s e l e c t e d

f o r t h e scouting tests.

Table X V I I l i s t s t h e s p e c h e n materi.al.s, tlieTr tre.de names, where

a p p l i c a b l e , and -the g e n e r a l a l l o y c l - a s s i f i c a t i o n s Lo which they belong.

of t h e materials were n i c k e l - r i c h a l l o y s .

80 wt $ Ni-20

wt

$ Co

Th.e

90

7d-b

'$ Ni-10

Most

w t $$ Co and

a l l o y s were n o n p r o p r i e t a r y arid were f a b r i c a t e d from

melts made i n Metallurgy Division f a c i l i . t i . e s . o b t a i n e d from commercial s u p p l i e r s .

The remaining r m t e r i a l s were

The platinum specj-men served as an e l e c -

t r o d e probe i n a n attempt by VPP o p e r a t i n g p e r s o n n e l t o i n v e s t i . g a t e t h e

e l e c t r o c h e m i c a l e f f e c t s during t h e f l u o r i n a t i o n process.

Rovever, c u r r e n t

d i d n o t flow through t h e probe and c o r r o s i v e losses irere recorded i n a regu-

l a r manner for the platihum specimen.

~ scou-ting t e s t material:;. ti.ons f o a11

46

Table XVITI shows t h e no~i~L:nalcomposi-

L. Brewer, "The Fusion and Vaporization O a t s or^ tile Halides, '' The C h m i s t r y and MetaLlurw of M i s c e l l a n e o u s I a t e r i a l s : Thcrmodynamics (ed. ~ J J Laurence L. Q u i l l ) National Nuclear Energy S e r i e s , DI v. IV lyB, McGrav-Kill, New York, 1930.


Table XVI. Melting and B o i l i n g P o i n t D a t a of Various Metal F l u o r i d e s Consti t u e i i t s of Material s U s e d i n t h e Volati l i t y P i l o t P l a n t ScouLilig Corrosion Tests" (Convertetl from OK)

F:leme n t Ni

Fe

co

cu A l

Fluori de

Mn

FeF

1027

FeF2

3

1202

CoF

102 f b

3

CuF CUF2

3

w2

M2

3 'TiF 3 C1.F

2

CrF

3

CrP4

CrF

Mo

5

MOP 5

("C>

Disproportionatcs

947

82'ib

AlF

Boiling P o i n t

1102

CoE2

TiF4

Cr

b

io27

MnF 'I'i

("C)

NiF2

A1F

Mg

Melt i.ng P o i n t

73Yjb

1357b

> 1272

1272

1263

2227

856

2027~

lo77b

13Vb

122Tb

142Tb

42'rb

28J-t

1.102

1100

277

b

212-lb b

1427 2?7

b

102b

UTb

77b

22p

~

~

.~~.

Brewer, "The Fusion and Vapori-zation Data of t h e Halides," The Chemistry and Metal.lurgy of Mfscell.aneous M a t e r i a l s : Thermodynamics (ea. by Laurence L. Q u l l l ) National Nuclear Energy S e r i e s , D7.v. I V 19B, McGraw-Hill, New York, 1950. bEs-timated OP 0btai.tied by E x t r a p o l a t i o n of Experimental Data by L. Brewer. CBernard Weinstock and J. G. Malm, "Some Recent Studi.es w i t h Hexafluorides, ' I .Basic Chemi~stryi n Nuclear Energy 28, pp. l2$-l29, 2nd Uni-Led Nati.ons InteraL.

n a t i o n a l Conference on t h e P e a c e f u i T s e s o f Ato1ni.c Energy, Geneva, 1958.


-

111

-

Table XVII. Corrosion Scouting Test Specimeii M a t e r i a l s Used in tile V o l a t i l i t , y Pilot P l a n t Mark 1 and Mark TI Fluorinators P

Material

L Nickel INCO

-_

Classi-fication

Ni

61 Weld Wire

Gold-plated L N i c k e l

30 w t $ T'Tickel-10 irk, $I Cobalt 80 wt $ Nickel-20 w t 4 Cobalt,

Nj Ni Ni-Co

N i - Co

Cobanic

Ni-Co

D Nickel

Ni -Mn

Ni - Cu

Mone 1

Nimoni-c

80

Inconel

NF-Cr-Il'e PJi - Co-Cr (+ Ti, AI, and ~ e )

Waspalloy TITGO 700

Mi -Co-Cr

X p u 80

Hastelloy B HasteLLoy INOR- 2

w

INOR-8 Hastelloy X

OFIIC Copper

Pla t inum

Ni-Cr

N i - Fe -Mo

N i-Mo- Fe

Ni - Mo -Fe

Mi-140 - Cr

-

N i -140 - Cr Fe Ni-Mo- Cr-Fe

cu

Pt


Tabie XVIII. Nominal Composition o f Corroslon Specimens from t h e V o l a t i l i t y Pilot Plant Fluorinazor

KateTial

Ni

L Ni“

99.47

weid wire Au-plated

(min)

1mca 61

L DJib D Ni SFHC Cu

Hymu 80 Cobanic

m ! o 700

93.00

79 55

45

90 R’i-10 Coa 90.02

57.65 77‘

48

(ball

57

(sal)

3astclloy

65

Hastelloy

60

B

1.i

INOR-2

INOR-8“

79

69.8

Nimonic 80c 7k.28

Mn

1.5

0.17 1.0

-

16

9.63 0.17 30.30

1.01

2.3

0.64

5.1 0.6

C

d

V

16

0.75

0.1

0.005

0.05

0.01t

1.42

bLtase metal same as L N i above.

9“1..T)+

2.42

0.026 0.020 0.19

0.01

0.06

28

0.4

0.1

25

5

0.12

16 5 0.1 16.5 6.9 0.08

20.38 0.05

‘Veni‘.or ciiernical analysis.

1

B

0.01

0.: 0.08

0.007

0.008

0.20

3.1 0.03 (mx)

irnax)

0.08

.(

0.15

3 . k 5 18-21,G.l

0.83 0.5

SI

5

0.0075

0.01

8.82 21.81 0.11

2.5

Zr

-

0.023 0.15

0.05

15

0.20

5 5.5

3.0

0.98

0.1

2 (rnau)

Chemical a n a l y s i s .

e I n c l u d e s cobalt.

20.13

i 18,7h

4.0

2.5

29

1.k

2.0-3.5

0.50

45

1.i’

Pt

4.75

(bal)

Platinum

‘ORET

0.25

A1

Goid alate = 0.0015 in. 0.05 95.6.

80 ~ i - 2 0 Coa 79.59 NIonela Inc one 1 ibsteiloy XC Waspalloy

Cu

Co

?e

0.11 1.0

Nominal Composition wt $ Ti KO Cr

0.X 0.2

3.78 0.311

0.75

(max)

0.6 0.005 0.007

0.i‘+0.008 0.23

“Jestinghouse c:iemlcal a n a l y s i s (Iieat 8M3).

0.m a (ma.)


- 113 R.

Test Method The s c o u t i n g specimens c o n s i s t e d of l e n g t h s of rod, sheet, or s p l i t

p i p e stock, o r combinations t h e r e o f , each approx

48-56 i n . long. They were

h e l d i n p l a c e i n th.e f l u o r i n a t i o n v e s s e l s by two methods.

Tluring t h e Mark I

f l u o r i n a t o r s opera-Lions, a l l specimens were welded t o t h e top b l i n d f l a n g e of bhe v e s s e l as shown. i n Fig.

I

When t h e Mark I1 v e s s e l was i n use s e v e r a l

3.

specimens were welded t o t h e i n s p e c t i o n p o r t f l a n g e i n a s i m i l a r manner w h i l e t h e remaining t e s t rods were h e l d i n p l a c e by metal connectors sr'ipping a â&#x201A;Źitt i n g prewelded t o t h e end of t h e t e s t rod.

The end f i t t i n g s were A n i c k e l

t u b i n g 1/2-in.-o.d.

x approx 3 i n . long and s e a l w e l d e d t o prevent t h e escape

o f process gases.

Fi.gclre $2 shows a cut-away view o f t h e Mark I1 VPP f l u o r i n a -

t o r i l l u s t r a t i n g t h e placement o f c o r r o s i o n specimens and. a t y p i c a l . t e s t specimen prepared f o r i n s e r t i o n .

A t o t a l of

31 t e s t specimens w a s exposed t o the f l u o r i n a t i o n environ-

I n each t e s t grouping a t l e a s t one 1, n i c k e l specimen w a s included as a

ments. con-Lrol.

Figure

53 shows a t o p vie-w of t h e f l u o r i n a t o r s i n d i c a t i - n g t h e placement

of t h e specimens i n terms of p o l a r geometry, t h e t e s t i n g o r d e r and i d e n t i f i c a t i o n number, arid c o r r o s i o n specimen numbers.

The c o r r o s i o n specimen nmctber i.dentifl.es

parti-cwlar f l u o r i n a t o r runs when specimens were i n p l a c e and a l s o i n d i c a t e s t h e t o t a l number o f speci-mens t e s t e d srimultaneously.

f l u o r i n a t i o n r u n s M - 2 1 through

L - l through L-4,

and L-5 through L-9.

for each run group.

t h e s e scouting i-uns.

C.

M-48, C-9

The major t e s t groupings were

through C-15, E-3 through

Figure

$4 d e t a i l s

E-6,

t h e process c y c l l n g

Tables I and V I summarize t h e o t h e r process d e t a i l s during

Reactions t o Environments A f t e r exposwe, the t e s t speci.mens were removed from t h e f l u o r i n a t i o n

v e s s e l s and subjec-Led t o dimensional a n a l y s e s and metallographic st11d.y. Figures

55

and

56

summarize -t;he maximum c o r r o s i v e l o s s e s found i n each major

exposure r e g i o n as determined by micrometer rxeasurements and o p t i c a l microscopy. Figure

55 d e t a i l s -the l o s s

data as a p l o t of m i l s per month, based on individ,

ual m o l t e n - s a l t r e s i d e n c e times, while Fig. 56 shows t h e l o s s d a t a in terms of


-

1111--

U N C L A S S I FlED O R N L-LR-DWG 49167

SPECIMENS WELDED DIRECTLY TO TOP FLANGE

/

/

TUBE PRE-WELDED TO SPECIMEN 'TO FIT TliREADEB FITTING

Fig. 5?. View of Mask I1 WP Fluorinator Vessel Showing Metbods of Corrosion Rod Placement.


-

115

-

Ut4CLASSIFIFD O R N L - L R - D W G 49168

SCH EDIJL E -.

.... Older o f Test ond Identification

No.

1 2 3 4 5 6 7 8

9

IO

11

12 13 14 15 16 17 18 19 20 21 22 23

24 25 26 27 28 29 30 31

Corrosion

.

Materiol

“L”

M21-Md8:1 M21-M48:2 M21448:3 M21-M48:4 C9-CI5:I c9-c15:2 c9-c15:3 c9.c15:4 E3.E6: I E3-E6:2 E3-E63 E3-E6:4 E3-E6:5 E3-E6:6 E3-E47 E6 LI-L41 Ll-L4:2 LI-L4:3 Ll-L4:4 LI-L4:5 L3.L4 LI-L4:6 L5~L9:I L5-L9:2 L5-L9:3 LS-L9:4 L5-L9:5 1_5-L9:6 L5-L9:7 L5-L9:8

‘Example: M21-48refers to runs when \ p e c i m e n wos e x p r e d ; is, fow rpecirne,>s rested siinultoneously during the “M” runs.

.

__

N~,.

nickel rod

“L” nickel

rod

‘ I nickel ” rod

“L” nickel rod INOR-2 rod “L” nickel rod ”L” nickel rod

H ~ t c l l o y“B” rod Inco-41 weld w i r e liiconel tube

M o d rod

RONi-IOCa rod ” L ” nickel rod

90Ni-ICCo rod

OFHC Cu rod Platinum

INOR-8 rod Au-plated “L” NI rod Inco-61 w e l d w i r e Inco-700 rod

Cobonic

Inco-61 weld w i r e “ L ” nickel rod “D” nickel sheet INOR-8 rod “L” nickel rod

Wvrpolloy rod

tiostelloy “ X ” p,pc

Hostelloy “W” sheet N i m o n i c “80” pipe

Hymu “80” rod

(:1)

refers t o lucnl g w u p number, h a t

Ffg. 53. Top V i e w oi’ WP Fluorinators Showing Placement Test Specimens, T e s t i n g Order, and Specimen Number.

or

Corrosion


11.6-

k

0 ct-1


P 6

E

...

- 1-17 -

il

I/


118

-


- llg

-

m i l s p e r hour, based on o p e r a t i o n a l f l u o r i n e sparge t i m e .

In b o t h f i g u r e s

d o t t e d and c r o s s hatched bars r e p r e s e n t bulk metal losses and. v i s i b l e i n t e r -

g r a n u l a r a t t a c k , respectivel.y, while s o l i d b a r s i - n d i c a t e a t o t a l loss of t h e specimen occurred a t t h e p o i n t i n d i c a t e d .

S e v e r a l specimens r e g i s t e r e d lower rates of maximum c o r r o s i v e a t t a c k

t h a n t h e L n i c k e l c o n t r o l rods.

INOR-8, alloys,

H a s t e l l o y W,

These specimens included. Xymu 80, INOR-2,

H a s t e l l o y X, Waspalloy, and t h e

I n particular,

mir

80 was

90

wt

$ Ni-10

wt

$ Co

s u p e r i o r to a l l t e s t specimens i n all runs,

although the specimen r e g i s t e r e d a m a x i m u m bulk loss r a t e of 11 mi.ls/mon-!Ai,

based on m o l t e n - s a l t r e s i d e n c e time, a t t h e v a p o r - s a l t i n t e r f a c e .

> 105 mils/month based specimen, one INCO-61weld

of c o r r o s i o n specimens, i.ndicat-i.ng c o r r o s i o n rates o f on m o l t e n - s a l t t i m e , was found f o r one L nickel-

Total. loss

w i r e specimen, and f o r t h e Has-telloy B, Nimonic 80, Inconel, Monel, copper, and

platinum specimens.

S e l e c t e d pliotomacrographs and photomi.crographs of samples from many

of t h e s e c o r r o s i o n specimens are p r e s e n t e d i n Append-ix A.

I n most cases, t h e

a r e a s of maximum a t t a c k are shown.

D, Discussion of R e s u l t s A wide v a r i a t i . o n i n r e s i s t a n c e t o t h e F l u o r i n a t i o n environment w a s found on. c o r r o s i o n specimens used i n t h e c o m p s t i b i l i t y t e s t i n g d e s c r i b e d .

The

v a r i a t i o n s i n c o r r o s i o n noted were a n t i c i p a - t e d because of t h e widely d.ivergent process c o n d i t i o n s .

Because the VPP has e s s e n t i a l l y been o p e r a t e d for r e a s i -

b i l i t y s t u d i e s , demonstration runsg and runs designed t o recover uranium from a v a i l a b l e f l u o r i d e salt mixtures, -the d e t e r m i n a t i o n of optimum p r o c e s s condit i . o n s r a t h e r t h a n t h e g a t h e r i n g of c o r r o s i o n d . a t a has been t h e p r e v a i l i n g

p h i l o sophy

.

I n many groups of r u n s a v i d e v a r i e t y of scouting m a t e r i a l s w a s used which were i n proximity.

This w a s recognized as b e i n g far from ideal f o r

c o r r o s i o n t e s t i n g , b u t l i t t l e choice was a v a i l a b l e under t h e circumstances.

Xowever, Run Group M-21-48 d i d c o n t a i n o n l y Lhe r e f e r e n c e mater?-al, L a i c k e l ,


- 120

-

and t h e r e s u l t s were almost as d i v e r g e n t as t h e d a t a obtai-ned i n r u n groups where as many as seven d i f f e r e n t materials were p r e s e n t i n the same system, The L n i c k e l r e f e r e n c e spectmen's mean r a t e of c o r r o s i v e a t t a c k w a s similar t o t h a t found on t h e walls of t h e correspond.i.ng p i . l o t plan-t; f l u - o r i -

n a t o r s , although l a r g e d e v i a t i o n s from t h e mean e x i s t e d .

While maximum

c o r r o s i v e a t t a c k occurred i n t h e vapor r e g i o n on t h e Mark I f l u o r i n a t o r and

i n t h e s a l t r e g - o n of t h e Mark T I v e s s e l , i n almost all. c a s e s t h e L n i c k e l

specimens showed maximum a t t a c k a t t h e p o i n t or vapor-salt i n t e r f a c e c o n t a c t . A n o t a b l e e x c e p t i o n w a s specimen

M-21&3:4,

t e s t e d i n t h e Mark 1 f l . u o r i n a t o r ,

which exhibi-ted f a i l u r e i n t h e upper vapor region. f7.iiortd-e dlrriilg t h e M-2l-M-Jc8

The a d d i t i o n of chromium

Run Group may have produced t h e vapor r e g i o n

f a i l u r e through mechanisms proposed i n S e c t i o n I. The i n c r e a s e d a t t a c k on t h e L n i c k e l specimens a t the v a p o r - s a l t

i n t e r f a c e p o s s i b l y r e s u l t e d from salt, a g i t a t i . o n a t t h e c e n t e r of the v e s s e l induced by tlie f l . u o r i n e ant3 n i t r o g e n s p a r g i n g through t h e d r a f t tube.

This

a g i t a t i o n could r e s u l t i n i n c r e a s e d e r o s i o n aiid vibrati.on of t h e specimens w i t h resultaril; l o s s of p r o t e c t i v e

filiiis.

1n a d d i t i o n , t h c l o c a t i o n may have

allowed primary c o n t a c t of t h e specimens w i t h t h e f l u o r i n e sparge b e f o r e the

l a t t e r reaciiei? t h e v e s s z l w a l l s .

However, t h e i n c r e a s e d c o r r o s i o n t o be ex-

pee-Led from t h i s e f f e c t was not noted on t h e A nickel. f l u o r i n e i n l e t kubes,

t h e d r a f t tube w a l l s , o r o t h e r f l u o r i n a t o r i n t e r n a l components d i s c u s s e d i n

S e c t i o n IT.

Tests on INCO-61. we1.d wi.re were intended t o provide d a t a on a n i c k e l -

r i c h a l l o y w i t h a d d i t i o n s n o t r e a d i l y a v a i l a b l e i n commercial. a l l o g s .

Besides

ni-ckel, t h i s m a k e r i a l c o n t a i n s s m a l l amounts o f Al, T i , Fe, Mn, S i , and Cu (Table XTIII).

Sj~ncet h i s material w a s used i n f a b r i c a t i n g t h e f l u o r i n a t o r s ,

t h e s e t e s t s provided a n indri.cation o f weld metal. behavior, although t h e weld

m e t a l a f t e r d e p o s i t i o n would have a c a s t stxuclui-e compared t o t h e wrought s t r u c t u r e of t h e weld wire.

IT"^

INCO-61specimens

showed g e n e r a ~ yana1ogou.s

b u l k metal. 1.0~s behavior when compared to t h e L n i c k e l specitileiis, i n t e r g r a n u l a r a t t a c k was foimd i.n t h e

rmco-61

speciuiens

However, no


-

121

-

The behavior of t h e gold-plated L n i c k e l c o r r o s i o n specimens i n d i c a t e d

t h a t no p r o t e c t i o n was provided by Lhe p l a t i n g .

Comparison wi-Lh L n i c k e l spec-i-

6 i n Fig. 55 shows comparable l o s s e s . On t h e b a s i s of s i n g l e exposures o f the 90% Ni-lO$

men number L-1-L-4:

Co and

80$ Ni-20$

specimens, cobalt; a d d i t i o n s seemed Lo improve t h e r e s i s t a n c e of' commercial

Co

n i c k e l t o t h e f l u o r i n a t i o n environment w i t h t h e one e x c e p t i o n of t h e high vapor-

s a l t i n t e r f a c e a t t a c k found i n t h e 80% Ni-20$ containing

45$ Co, w a s

Co specimen.

The cobanic a l l o y ,

t e s t e d o n l y in t h e f l u o r i n a t i o n vapor phase and showed

g r e a t e r l o s s e s when compared w i t h L n i c k e l .

T h m , f u r t h e r invest.fgation O C

n i c k e l - b a s e a l l o y s w i t h less t h a n 20% Co seems warranted.

Because '&e most

c o r r o s i o n - r e s i s t a n t Ni-Co all.oys a r e experimental, t h e i n v e s t i g a t i o n should

u l t i m a t e l y inc1ud.e t h e d e t e r m i n a t i o n of mechanical and p h y s i c a l p r o p e r t i e s and fabricability

.

Tie n i c k e l - r i c h copper specimen, Monel., provided. poor r e s i s t a n c e t o

t h e f l u o r i n a t i - o n environment d.uri.ng a s i n g l e t e s t run.

The specimen r a i l e d

completely a t t h e v a p o r - s a l t i n t e r f a c e .

'The D n i c k e l , c o n t a i n i n g about 5% Mn, and developed f o r improved r e s i s t a n c e t o s u l f u r a t t a c k i n o x i d i z i n g atmospheres a t e l e v a t e d temperatures, p r e s e n t e d somewhat h i g h e r l o s s r a t e s t h a n t h e L n i c k e l specimen simultaneously exposed,

"tie D n i c k e l specimen p r e s e n t e d a d i f f e r e n t geometry t o t h e corrodents,

s h e e t vs rod, b u t t h a t d i f f e r e n c e i s no-t b e l i e v e d t o have been s i g n i f i c a n t i n prod1icin.g -the higher r a t e s of a t t a c k .

A s expected, t h e Nimonic 80 a l l o y , c o n t a i n i n g 20$ Cn. and approx

2.5% T i , e x h i b i t e d s u b s t a n t i a l l y g r e a t e r b u l k l o s s e s t h a n t h e corresponding L n i c k e l specimen.

ReTerence to ,Table -XVI shows t h a t chromium and.titanium.

can form h i g h l y v o l a t i l e f l u o r i d e s at t h e i r h i g h e r valence s t a t e s .

A hrigh- temperature , o x i d i z a t ion- r e s istaiit, n i c k e l - chromium- i r o n a l l o y ,

Inconel, has been mentioned as b e i n g u s e f i l i n c o n t a c t w i t h f u s e d f l u o r i d e s a l t s . &.ring t h e s i n g l e t e s t iri t h e f l u o r i n a t i o n environment, t h e specimen completely f a i l e d a t -the v a p o r - s a l t i n t e r f a c e , and also e x h i b i t e d a r a t h e r high vapor-phase

attack


-

122

-

The Ni-Co-Cr a l l o y s , Waspalloy and I N C O TOO, d.?ffered s i g n i f i c a n t l y

i n attack.

Sarnp1.e~of INCO TOO were a v a i l a b l e only- for a s a l t - p h a s e t e s t and i n t h i s regl.on had a bulk l o s s rate

(L-l-L-4:4)

>

100 mils/month which

coiisi d e r s b l y exceeded. t h e L n i c k e l specimen exposed simultaneously.

The

Waspalloy speci-men showed a r a t e of a t t a c k s l i g h t l y Less t h a n t h a t of a corresponding T, ni.ckel specimen,

Fur.ther i n v e s t i g a t i o n o f Waspalloy seems war-

rat?l;ed, although ii should be remembered t h a t t h e a U o y ages a t 750째C, a temperature only s l i - g h t l y higher than t h e f l u o r i n a t o r o p e r a t i n g range.

Thus,

temperature excursions, which may be encountered i n extended o p e r a t i o n s , might d r a s t i c a l l y reduce Lhe d u c t i l i t y of t h e material-,

The H J T ~ ~ ~ specimen, -~O Ni-Fe-Mo,

presented. t h e b e s t resis'cance t o

c o r r o s i o n o f a.ny o f t h e speclimens t e s t e d i n c l u d i n g t h e L n i c k e l r e f e r e n c e

material.

This a l l o y i s commercia1.l.y avai.lab1.e and s i x miniature f l u o r i n a t o r s

have been f a b r i c a t e d f o r compa-Libility t e s t i n g w i t h N a F - Z r F

4 and

LiF-NaF-Zi-F,~,~

s a l t mixtures by t h e Volat,i.li.ty S t u d i e s Group of Chemical Development S e c t i o n A. The e s s e n t i a l l y Ni-Mo-Fe alloys, K a s t e l l o y B and W, a g a i n showed t h e

v a r i a n t behavior c h a r a c t e r i s t i - c of t h i s -test s e r i e s .

The Hastelloy-B specimen.

bad extrerneljr poor r e s i s t a n c e arid. Tailed. completely 22 i n . above t h e s t a t i c sal.1;

level.

Since t h e specimen w a s exposed d u r i n g tile Mark I o p e r a t i o n , t h e h i g h

vapor-phase a t t a c k evidenced. a t t h a t time may w e l l have inT1uenced~t h e behavior

of H a s t e l l o y B.

The Hastelloy-W speci.men, i n place during a re1a.tiveLy low

c o r r o s i o n r u n s e r i e s , L-$-L-g,

e x h i b i t e d s l i - g h t l y lower l o s s e s when compared

wi.t'n t h e L n i c k e l c o n t r o l specimen.

This vas becaiAse: of t h e i n t e r g r a n u l a r

a t t a c k excperienced by t h e T, n i c k e l .

One of t h e e a r l y manj.festations o f t h e Ni-Mo alloy s e r i e s developed

a t ORNL f o r fused.-fluoride s a l t use w a s I N O R 2.

The s i n g l e INOR-2 speci-men

t e s t e d had c o r r o s i o n r e s i s t a n c e s u p e r i o r t o e i k h e r of t h e L n i c k e l specimens

exposed c o n c u r r e n t l y .

Lack o f a d d i t i o n a l material has liiiidered f u r t h e r corrosi.on

testj-ng. The Ni-Mo-Cr-Fe

al-loys t e s t e d , INOH 8 and Has.Lrlloy X, had c o r r o s i o n

r e s l s t a n c e compaxhable t o t h a t of t h e L n i c k e l r o d s exposed simultsneo-i1.sI.y.

As

described i n S e c t i o n 111, m i n i a t u r e f l . u o r i n a t o r s were f a b r i c a t e d from INOR 8 a.n.t?. t e s t e d .

These tests d i d no-L i n d i c a t e any s u p e r i o r j - t y over commercial nickel..


-

123

w a s exposed to t h e Mark I1

A s i n g l e copper specimen, L-*L-6:'7, environment.

The speci.men f a i l e d . conpletely i.n t h e middle vapor reg?'.on.

Cu-

p r i c f l u o r i d e was considered most l i k e l y Lo form under the excess f l u o r i n e conditions present during t e s t i n g .

Although C u F 2 h.a:; a meltring p o i n t of

~ p p r o x950째C and should have a f f o r d e d p r o t e e t i o n to the p a r e n t me-tal, copper's l a c k of r e s i s t a n c e t o oxidizing eiiv-ironinents a-t; _Tl.uorilzation temperatures may

exp1ai.n i.ts poor performance The platinrim specimen was completely severed by c o r r o s i v e a t t a c k 1 jl

t h e iupper vapor r e g i o n .

This wire was itrtended t o serve

'out, never c a r r i e d c u r r e n t .

8.8

an elec.t;ro(le probe,

The reason f o r t h e ex-trme yate o f a.ttack: on

platinum s e e m t o be t h e .instabi.li.tyof PtF

G

cotiipse at 280째C (Table XVI).

which has been r e p o r t e d t o de-

Whereas t h e L n i eke1 specj.mens exhibi'wd i.ntergra.iiu1a.r a.t-t;a.ck, v e r y

few i n s t a n c e s of t h i s mode of attack were noted on t h e other specrimens tes-Led.

S e c t i o n s I and TI d e s c r i b e tile rnechanisrii.:; presimably operatj.ng on 1, nickel. E.

Future S-t;uc'l.ies

The corrosion r a t e s for a l l scoutiiit: inateri.al.s tested. t o d a t e appeal-

-to be excessive f o r long- tim? use.

T1ierefore, additional. ~l.uori.na-i;.iunscouti.ng

c o r r o s i o n tests of tbe type descri-bed have been planned.

Pa:rt,.iLcul-arr enph.a.:;:is

ha:; been placed. on b i n a r y nickel-rich alloys c o n t a i n i n g van-i.ou s amounts of

Fe, Co, Mro, Mg, and 141. The l a t t e r two elemen-Ls have n o t been corisiilered i n

previous experiments because o f t h e f a b r i c a t i o n , age hardt?r;iing, o r o t h e r

d i f f i c u l t i e s characterfstic when alloyed i n a p p r e c i a b l e cpsaatities w i t h nickel.

Gnly a few nickel-base commercial al.l.oys c o n t a i n i n g magnesium a-!d. aluminum i n conhination w i t h other i n g r e d t e n t s have been avai.lable and s L r i l L l'ebrer have

been commercial as Ni-Mg o r N i - A 1 b i n a r i e s

Yet, aluiiiinum and rnagmsium a:r*e

known t o f o r m f l u o r i d e s a t t h e i r h i g h e s t valence s'iates, which have highel-

melting p o i n t s t h a n NiF

2' To d a t e , Fe, Co, Mn, Mg, and Al i n t h e q u a n t i t i e s slnom i.n Table XIX

have been added t o i n d u c t i o n melts of n i c k e l and cast; i n t o 1 - i n . rounds.

After

s u i t a b l e homogenization t r e a t m e n t s of t h e cast?ngs, t h e rouiids were cold swaged


- l2k

Table XlX.

-

Proposed Noncommercial Binary A l l o y s f o r Corrosion Tcs1,j ng in the Vo1at.i 1.Lty Process Fluorinatir,n Environment.

A l l o y Group NiFe

95

5

90

10

80 NiCo

95

5

90

10

NiMn

98

NiMg

99.95 93.9 99

2 0.05

0.1 1. .0

99 97

NiAl.

I__._

20

............ ....................

..

1.

3 ~

-

.

-

.-

....l.l____lll--sl

I___


-

1.25 -

rods and h.yd.rogzn annealed.

.to 1/4-in.-diam

The rods have been c u t t o proper

l e n g t h s , e l i d f i t t i n g s a t t a c h e d by s e a l welding, ad. are p r e s e n - t L y - a w a i t i n g

placement i n a VPP f l u . o r l n a t o r .

In. a d d i t i o n , hi-gh-puri t y va.cuum-iiiclted n i c k . e l has been c)btaFnEtd and

f a b r i c a t e d i.nto .the proper t e s t speci.iiien shape f o r examjining +,he r e s i s t a n c e

of t h a t , ma-terial t o the f l u o r i n a t i o n environment

V.

e

Argonne N a t i o n a l Laboratory F l u o r i n a t i o n Corrosion S t u d i e--s The Chemical Engineering D i v i s i o n of Argosne National Labora-tory has

k[ A p o r t i o n

clone extensive work on nonaqiieous p r o c e s s i n g o f i r r a d i a t e d fuels.

of their e f f o r - t has been on s t u d i e s o f f1uorid.e v o l a t i l i - L y p r o c e s s e s .

A re-

view of one of t h e Argonne N a t i o n a l Laboratory s t u d i e s on materials compat,Ib i l i t y i n u simulated fluorrirmtion environment i s i n c l u d e d here f o r compari.son w i t h ORHL data. A.

T e s t Method

Fliio:r*ination c o r r o s i o n t e s t s were conducted. on cou.pons ot' L nickel., ( r e f h8) D n i c k e l , B a s t e l l o y R, and INOR 1. The coupons were contai-ned i n a

vessel. which had a n i n n e r l i n e r and i n t e r n a l piping f a b r i c a t e d from A nickel. The coupons, each 8 i n . long x 0.5 i n . wide x 0.032 i n . t h i c k , were w i r e d . t o -

gether t o form a simulated d r a f t tube of square cross s e c t i o n . of .the wire was n o t i n d i c a t e d .

The corqiosi-tion

The nomiinal coniposition of t h e f i r s t t h r e e

materials l i . s t e d above has been given i n Table X I X .

Another of i2ie e a r l y ex-

p e r i m e n t a l a l l o y s , INOR 1, s i x d i e d i n the development of INOR 8, had. a r?.orninal composition of

0.01 wt

$ I

c.

78 TJ"L 76

Mi--20 w t

$ Mo-0.5

wt

$ &-0.5

wt

$

Si-0.25

+it $ Fe-

The s i m u l a t e d . d r a f t tube w a s p a r t i a l l y immersed i n a b a t h ot' equi-

molar NaF-ZrF4 so t h a t t h e v a p o r - s a l t i n t e r r a c e w a s approx 3 i n . up Prom the 1-

t ' R . C. Vogel and R. K. Steunenberg, "Fluoride V o l a k i l i t y P r o c e s s e s f o r Low Alloy F i ~ e l s'', Symposi.iim on t h e R,eprocessing of I r r a d i a t e d F u e l s Held a t Brussels, Relgium, May 20-25, 1957, Book 2, S e s s i o n IV, pp.4 9&553, rID-'[5~l~..

48L. Hay-:;,13.

3reyne, and W. S e e f e l d t , "Comparative T e s t s of 1, Nickel, D Nickel, H a s t e l l o y B, arid IMOK 1," Chemical Engineering Uivlisiort Sunimary. ~ p o r t ,~ i i ~ ~ y u, g u s t ,September, 1958, A~~-5924-, pp. Q-52


The b a t h was h e l d a t 600°C while f l u o r i n e o r helium

bottom of Lli? coupons.

w a s iiitroduced c e n t r a l l y beneath t h e melt s u r f a c e s a t r a t e s of approx 0 . 1 standard liters/min.

During i h i s t e s t series, t h e f l u o r i d e s a l t s were kept

molten Tor a t o t a l of 216: hr and f o r 63 hr of t h a t time Pluorine w a s spa-rged The IJ-rocess gases were i n t r o d u c e d on a c y c l i c b a s i s , i . e . ,

i n i o t h e ’oath.

f o r 7 hr/day f l u o r i n e was spargpd while helium w a s sparged Tor the remaining

17

h r of a day.

57 and 58 i l l u s t r a t e t h e c o r r o s i o n l o s s e s obtairipd d u r j n g t h i s t e s t s e r i e s . F i g u r e 57 i s a b a r graph where bulk metal losses as Figures

determined by micrometer measurement an& a d d i t i o n a l l o s s e s as deterrnined by

metallographic examination have been convertpd to m j Is/month o r molten- salt, residence t i n e . sparge t i m e .

Figure

56

i s a similar graph p l o t t e d as mils/’nouj- of f l u o r i n e

Rates have been p l o t t e d i n s t e a d of o r i g i n a l . d a t a f o r comparison

w i t h ORNL d a t a .

B.

Discussion o f R e s u l t s

1 . -

The corrosi~onl o s s e s i n t h i s Argonne National L a b o r a t x r y t e s t s e r i e s

suggest t h a t INOR 1 w a s t h e most r e s i s t a n t t o t h e t e s t environment, while t h e

1, n i c k e l r e f e r e n c e material f a r e d poor1.y.

Tnis i s a t t i - i b u t e d t o the e x t e n s i v e

intergran.ul.ar a t t a c k on the L a t t e r material., p a r t i c u l . a r l y a t t h e v a p o r - s a l t interface. Comparison of t h e Argonrie Nati-onal Laboratory c o r r o s i o n r e s u l t s w i t h t h o s e o b t a i n e d a t ORNL i s d i f f i c u l t because of d i f f e r e n c e s i n t e s t procedures which i n c l u d e f l u o r i n e flow r a t e s , specimen l o c a t i o n and. geometry, and s a l t compositions

However, Argo-me‘ s r e s u l t s on L ni.ckel f i t t h e c o r r o s i o n

l i m i t s determined f o r t h e ORNT, s c o u t i n g c o r r o s i o n r e f e r e n c e specimeiis i n t h e

s a l t and at the s a l t - v a p o r i n - t e r f a c e s .

Vapor-phase specimens are n o t r e a d i l y

comparabI.e, si.nce Argon-ne specimens were o n l y 3 t o

surface

.

4 ill.

above t h e sa1.t

The Argonfie N a t j o n a l Laboratory H a s t e l l o y B and t h e D n i c k e l specimens

g e n e r a l l y had l e s s a t t a c k t h a n s c o u t i n g specimens a t ORNL.

The d.ifferences may

be a t t r i - b u t e d t o more severe opera+,:ing c o n d i t i o n s i n t h e ORNL p i l o t p l a n t fluorinatmr.

Si.nce no I N O R - 1 specimen had been t e s t e d at ORNL, no comparisons

could be derived.


UNCLASSIF iED

QRNL-LR-OWG

49!69

L NICKEL

C bICKEL

!

HASTELLOY 3

i

INOR 1

I

1

1 j

- METAL

LEGEND V-VAPOR I - VAPOR SALT INTERFACE S - SALT LOSS/MICROMETER MEASUREMENT

- !NTERGRAkULAR ATTACK/METALLOGRAPHIC E X A M

- S UBSU R FAC E V 3 I DS / M E YA iL O 5 RAP H IC

E X A hl

MAXIMUM LOSS SHOWN IN EACH PHASE

3

15

26

25

30

65

mils/rno

( B A S E D O N SALT RESIDENCE T I M E )

Pig. 57. Summczry of Corrosion on C0;lporis Exposed t o a F l u x i n a t i o n Environment by %he Argorne ITst%cnsl La3oratory.

70


>--cn J W Y

-.I

2 z

......

-___ .........

-

-

-

-

128

__ ........

z

0 W

0

w J

W

t-

z

E

111

W

LT 3

cn

a

0 Q

LL W

t-

w

5

5 Q

cn

[LE

2

a X W

2 I n

u

Q J

0

0 J U I--

2

W

\

..J

0

Q

t-

K

a

3

..J

a

W

rT ,...

(3

a

cn z a

\

Y 0

E k-

Iy

0

w kw

5

I

(*

..J

l

I cn

001- c> -

a n

l

'ZaQ >>cn

I

> - W .J

U k-I

I

W z z

? 0

0

"!

L

0

0


-

129

-

Close cooperation has been maintained with t h e hrgonne National. Laboratory on t h e s e l e c t i o n and. t e s t i n g of' candi.date m a t e r i a l s of c o n s t r u c t i o n f o r use i n t h e f l u o r i . d e v o l a t i l i t y process.

I n addition t o materials research

as a means of c o n t a i n i n g t h e f l u o r i n a t i o n environment, Aryonne N a t i . o n a l Laboratory has s.uggested three o t h e r approaches.

These have been the use of

(1) cold wall f l u o r i n a t i o n vessel, ( 2 ) a spray tower f l u o r i n a t i o n , and

(3) 1.ower melting s a l t s .

"c9

JFurther work on t h e s e approaches has been covered

i n t h e Argorine N a t i o n a l LaboraLory Chemical Engineering Uivf s i o n Surmiary Reports.

Vi.

Supplementary V o l a t i l i t y P i l o t P l a n t Equipment The o p e r a t i o n of t h e VPP n e c e s s a r i l y i-ncluded the i i s e of a nuljlber of

au-uiliary components such as -traps f o r r a d i o a c t i v e prodiic-Ls, absorbers, valves, f i t k i n g s , f l u o r i n e disposal. systems, and p i p i n g .

E a c h oâ&#x201A;Ź t h e s e are si.ib<ject t o

various corrosj-ve c o n d i t i o n s i n c l u d i n g fl.uorine, uranri.ii.m h e x a f l u o r i d e , fused fluoride salts, e t c .

Thu.s,

successful o p e r a t i o n of' t h e v o l a t i l i - t y process

r e q u i r e s t h a t m a t e r i a l s be s e l e c t e d a p p r o p r i a t e for t h e p a r - t i e u l a r condit-ions

oi' s e m i - c e .

Construction of t h e p r e s e n t system w a s p r e d i c a t e d on tlie knowledge

a v a i l a b l e a t t h e time and as operatirig experience has been gained t h e s e p a r t s

have been examined t o v e r i â&#x201A;Ź y the o r i g i n a l assumptions.

I n most c a s e s the metal

s e l e c t e d appears t o give s a t i s f a c t o r y servi.ce and f a i l u r e a n a l y s e s have sug-

gested a l t e r n a t e metals i n t h e case of t h o s e which proved. unsuitab1.e.

The

d e t a i l s of t h e f i n d i n g s o f t h i s i n v e s t i g a t i o n a r e p r e s e n t e d i n Appendix 3 .

The a u t h o r s wish t o ac!aiowl.edge t h e a s s i s t a n c e gi.ven by t h e Metallography S e c t i o n of t h e Metallurgy Division, by personnel of the Spectrochemical. Group and the S p e c i a l Analyses Laboratory of tlie AnaLy-tical Chemistry Division, and

by t h e Graphic A r t s and Pnotography Departments, A p o r t i o n of t h e c o r r o s i o n e v a l u a t i o n s repori,ed i n t h i . s docunient and t h e accompanying i l l u s - l x a t i o n s a r e t h e work of t h e Corrosion Research DivFsion,

SatteI-le Memor i a1 I n s t iLute, and t be i r cont r i.b-iiti o n de s e r v e s spe c ia1 me ut i o n

here.

't9

A. Goldman, T r i p Report, ANL, t o W. D. Amly, June 12,

1958.


-

130

-

Thanks are due t o t h e many personnel of t h e Chemical Technology D i v i s i o n working on i h e ORNL F l u o r i d e Vol a t i l i ty Process who a i d e d i n g a t h e r l n g p r o c e s s

daia or Ti? reviewing t h i s r e p o r t .

S p e c i a l t n a n k s a r e due S. H. DeVan, X. E . doffrnaa, and

I).

A. Douglas, Jr.,

for t h e i r const,ructive a p p r a i s a l of p o r t i o n s o f t h i s r e p o r t and t o the

Meiallur~yDivi s i o n Iteports O f f i c e f o r t h e i r p a t i e n t iyping and c a r e f u l p r e p a r a t i o n of t h e material. f o r reproduction. BIBLlOGWHY

G. I. Cathers and R. E . Leuze, "A VolatT-lization Process for Uranium Recovery, ' I P r e p r i n t 2'78, Paper p r e s e n t e d a t Nuclear Engineering and Science Congress, Cleveland, Ohio, Decembei- I.?-l5, 1955; a l s o p r i n t e d i n "Selected Papers, I ' Reactor O p e r a t i o n a l Problems, 2, Pergarnon Press, T,ondon, 195.1.

G. I. Cathers, "Fluoride V o l a t i l i t y P r o c e s s f o r :iigh-"lll-oy Fuels, Symposium on t h e_._ lieprocessing of I r r a d i a t ~ dFuels, Held a i B i u s s e l s , I_^.-_Belgium, TSD-753h, Book 2, pp. 560-5'13, May 20-25, l 9 5 ' j .

I _

G. I. Cat,'ners, M. R . Bennett, and R. I,. J o l l e y , 'Yhe Fused S a l t F l u o r i d e ~9 V5)'o l a t i l i t y Process f o r Recovering Uranium, om~-2661 (Apr i 1,

_ I

'I


Fig. 59A. Cross Section of Interface Region Sample iâ&#x20AC;&#x2122;rom I, Nickel Corrosion Specimen ( R i m s L - F L - 9 : 3 ) . I n t e r i o r circumference of ivliite circle indicates original. size. As-polished. 1OX.


Fig. 60A. Cross Section of S a l t Region Sample from Gold P l a t e d T, Nickel Corrosion Specimen (Runs L-1-L-4: 2). T n t e ~ i o rC J rcimference of : d â&#x20AC;&#x2122; n i t e e I r c l e indicates o r i g i n 8 l size, .b-polished. 15X. Unc Las a i f i e d

Fig. 6053. Portion of Fig. 60A. Typical Surface ana Microstructure. Intergranular attack Etchant : mo3-Hpo4 ,. 200x. a


- 135

-

Fig. ~ I A .Cross Secti.on of I n t e r f a c e Region Sample from IiXCQ-61 Weld Wire Corrosion Specimen (Runs L-?3-L-4). I n t e r i o r circumference of white circle indicates o r i g i n a l size. As-polished. 15X.

~ i g .G ~ B . P o r t i o n 02 Etchant: Concentrated HNQ

Gu. Typical 2OOX. 3'

Surface and Microstructure.


- 136 -

Flg. 62A. Cross Section of Interface Region Sixaple from INOR-2 Corrosion Specirnen ( h i s C - P C - 1 5 : 1). T n t e r i o r circumference OJ? white c i r c l e indicates origf-nal s i z e 85~.

P o r t i o n of Fig. . & ' 6 Chrormium regia. 20OX.

Fig. 623.

Etchant:

Typical. Sul-race and Microst-ructure.


-

1

137 -

Unclassified

W

Fig. 63. Section of Vapor Region Sample from Hastelloy B Corrosion Specimen (Runs C-9-C-15: 4) Showing Typical Surface and Microstructure. Etchant: Chromium regia. 200X.


- 138

-

U'

a

0

.e

Fig. 64. S e c t i o n of Vapor Region Sample from T n c o m l Corrosion Specimen (Runs E - F E - 6 : 2 ) Showing Typical Surface and Microstmcture. Etchan?.: Modified

aqua regia.

200X.


- I39 -

Fig. 65. Section of Vapor Region Sample f r o m M o m 1 Corrosion Specimen (Fkms E-3-4-6: 3) Showing Typical S u r f a c e and Pillcrostructure Etchan-t: HC H 0 :RNO :HCI. 200X. 2 3 2 3 I


-

140 -

Fig. 66. Section of' Vapor Region S q l e from OFHC Copper Corrosion Specimen (Kuns 13-3-13-6: 7) ShowLrag Typical Surface and Microstructure. Etchant: rn40K: %O*. 200x.


-

141 -

67A. Cross Section of Interface Region Sample from 80 Ni-20 Co Specimen (mas E-+E-& 4). Interior circumference of white c i r c l e indleates o r i g t n a l s i z e . Combination of grain s i z e ma etchant presents a relief appearance because of l i g h t . Etchant;: HNO :rgS04. l5X. Pig.

CQPrOSiQIl

3 L .

Pig. 67B. PortZon of' Fig. 6 l A . Etchant: Concentrated fQl0 2OOX. 3"

Typical Surface and Microstructure.


-

142

-

Cross Section from Interface Xegion Samp1.e f r o m 90 Hi-1.0 Co Fig. 68A. Corrosion Specimen ( ~ u n sE-~-E-G;: 6 ) . I n t e r i o r circumference of white c i r c l e i n a i c a k s o r i g i n a l s i z e . E - t c b u t : HNO : H SO

3

2

4’

i ,

Fig. 6 8 ~ . Pol*tion of Fig. 68A. E t c ’ l w t : DFlute EWQ 200X.

3‘

Typical Surface

ana Microstructure.


-

143 -

L

Fig. 69. Longitudinal Cross Section of Vapor Reglon Sample from Plati.num Corroslan Specimen (Run E-6) Showing Typical Surface and Micmstmcture. Cathodic vacuum etch. 2QOX.


.. $'%e.(On.

Cross Szctioii of Interface Eegion Sample Crofii D NickeJ. Coi-rnsion Specimen (%ins L-pL-3: 1). In-Lerior of' white liner; indi.cates o r i g i n a l . si.:ze. As-polished, LOX. .

Fie. (OH. P o r t i o n oP F i g . 70A. ]Stchant: KCN-(NII ) s o POOX.

4223'

Typical Sixinace an? M i c r o s t r u c t u r e .


-

1145 -

F i g . 71.R. Cross Section o f S a l t Region S a q l e Prom INCO-7OO Corrosion Specimen (2luos L-1-1,-4: 11). I n t e r i o r c i r c d e r e n c e of white c <rcle indicater; origin?l. specimen s i z e . As-polishecl. 5X.

Fig. 71B. P o r t i o n of Fig.

Cathodic vac",uum etch.

2OOX.

7M.

Typical Surface and Microstructure.


- 146 -

F i g . '72. Cross Section of Vapor Region Sample f m m Cobnnic Corroslsn Specimen (~unsL-I*-Z-lt: 5). I n t e r t a r circumference of w h i be c i r c l e indicates original size Etchant,: Concentrated HNO 1OOX. I

3'


Fig. 7318. Portion of Fig. 7%. T y p i c a l Mcrostnrcture and Surface Showing 1ntergrmul.ar a t t a c k " Etehant: Chromium regia. 2WX.


- 148 -

F i g - 7)+A. Cross SPction of I n t e r f a c e Regton Sample f r o m Waspalloy Corrosion Specimen (Runs L - F L - 9 : ' ) . Tnterior circLirnfercnce of' w h i t e c i r c l e i nrij c a t z s original si e . As-polished . 5X.

F i g a 74B. P o r t i o n or k ' i g . E t c h a n t : Aqua 1-egia. 2OOX.

('1~.

' i y p ~ c s isumace a n d Microstructure.


- 149 -

Fig. 7>U. P o r t i o n of Fig. ‘(51‘t* Typical. :;urfal-.., Etchant: Chromium r c g i a . 2OOX.

arid Pili c r o s t m c t u r e .


. -..

. . ' *

..

..

.

. .

. I

*.

.

I jpLcal

r,

1 .

<

.,* .

c

'

I-

-

Suri'6i.e and Mirrostruc'cure.


F i g . 77A. Cross S e c t 3 . m of Salt Region Sample from NLmon1.c 80 Corrosion Specfmen (RUES L-FL-y:’-(). I n t e r i o r of white l i n e s indicate:; o r i g i n a l thickness. As-polished, XOX.

*

.. . .._

Fig. 77B. P o r t l o n of Fig;. ‘77P,, E.tchaazt: Aqua r e g i a . 21oOX,

Typical Surface and Mfcrostmcture.


I

$? i

ri

a:

k

0

r?

,

k

u? 0

V

4

-r

Q


APPENDIX U

c


Suppk m e n t a r y Volat i 1.i~ t y P i l o t P l a n t E qu.ipme n-L S e c t i o n s I a n d ii have descri-bed r e a c t i o n s t o t h e p r o c e s s envi.ronment of VPP 1, n i c k e l f l u o r i n a t i o n v e s s e l s

e

Other i.niportant component:; u.sed i n the

f l u o r i n a t i o n c y c l e o f -tile f l u o r l d e v o l a t i l i - t y p r o c e s s have been examined Torr cGrrosi.on r e s i s t a n c e to t h e i r l o c a l environments

.

The components iricl.ide a

CP.P t r a p , a waste-salt l i n e , the a b s o r b e r vessels, v a l v e s and f i t t i - n g s , coin-

p o n e a t s i n t h e f l u o r i n e disrjcjsal sys-km, and s e l e c t e d sectY.on:; from t h e

Figure 79 il.1.iistrates the reI.at,ive p o s i t i o n s of t h e s e

p-ixxess gss l i n e s .

components i.n t h e p i l o t pla-n-'i.

Cormlexible Radioactive Products T r a u To d a t e , two C.W t r a p s have been ul,Tlized i n t h e VPP.

l'he

tl-q

exan1Tned

was t h e second used. and was i n service d u r i n g .the Mark 11 f l u o r i n a t o r ' s l i f e time,

RS

ha:; been d e s c r i b e d p r e v l o u s l j r

f a b r i c a t e d ~from a

5-h.

iii

Secti.on Tm. This vessel was

nched.-kC) Incoriel pipe,

NaF p e l l e t s t o scn.lb the f l u o r i n a t o r e f f l u e n t c

remove Z r F

I!-

and CrF

5

31 i n . long and it c o n t a i n e d

ea:;.

The trap was dksigmeci. t o

and p r o v i d e s a c e r t a h a-inount of Tadi.oac1;ivt> d.econt;am.i-

nation. Ta11l.e XX su~imarizest h e exposure eondi.ti.ons f o r t h e trap. A complete ckscriptrion of t h e performanee o:P the CRP t r a p has been published. 50,51,52

A f t e r t h e Mark 11 f l u o r i n a t o r was taken. off stream, trepanned s e c t i o n s

were i~emovedfrom the CRP t r a p a i d s e n t t o SPII f o r c o r r o s i o n anal.yses.

Figxre

80

il1iistrates t ~ i es e c t i o n s removec~.

bkcrosI2opic examination of t h e samples at 20X revea1.E.d o - u t l t n i n g of t h e

Tncoiiel g'i-alns and an etched surface wi-Lh i n c r e a s e d attack noted a t Section B-T.

>- i)- C.

L. Winitmarsh, Reprocessing of AF3 Riel, Volat?.l.i.t;y Pilot Plant-.-.9 Runs

~ and E-2, i ~~-59-5-1.O~--~iS-1-~59). r-1

3LC.

L. Whitmarsh, Reprocessimg of APE Fuel, V o l a t i l i t--y -- Pilot P l a n t Runs,

E-3 through E-6, CF-59-3-73 CT)

(L4ugust

26, 1959).

'C. 1,. Whitniamh, Uraninm Xeeovery from S0diu.m Zirconium F1uorid.e Sa1.t; Mixtu>?en, V o l a t i l i t y P-il0-t P l m t Rims, L - l through L-9, CF-59-9-2 (Sep.l;ernlJer 30, 1959)

.


r

m a

n W

3

5

a

a

- 156 -

I L


0 0

z

4

0

0

0

E

0 3

M

A

%

f

L n

0 0

z

3

0 0

E

cu

CI

Fc

-3

0 0

E

4-

1.n

% LA

0

cu

-.

R

f

c\J

Fc


- 158

U NCL ASS1 F I E rj ORNL-LR-DWG 494 71

I

t

3 in.

8.5 in.

\

NaF PEl

ET LEVEL

M-T

26 in.

/â&#x20AC;&#x2122;

9-T

Pig. 80.

,

Locati-on of Specimens Trepa-wed from the Iriconel CRP Trap*


- 159

-

Df.rnensiona1 a n a l y s e s were performed on t h e s e c t i o n s as w e l l as a microscopic exarnj.nati.on.

A surnmary of %he c o r r o s i o n l o s s e s found by- RMI perooiinel i s

p r e s e n t e d i n Table =I.

rn~ixiniimt o t a l l o s s e s t o

Included. 7.n t h e t a b l e i s a column converting the

it

mils p e r hour r a t e based or1 fluorine ex_no:~.retime

at, o p e r a t i n g temperature f o r t h e v e s s e l .

A max:i.niim t o t a l corr.oo.i.on attack

rate oi" 0.1-16rnrils/hr occurred i n t h e I-ower s e c t i o n of t h e -trap which sus-

tai.ne d t h e h i ghe r ope r a t i n g temperat ures *

O p t i c a l microscopic examination of s e c t i o n s removed from t h e t r a p

r e v e a l e d i n t e r g r a n u l a r attack on both tiie i n t e r i - o r and e x t e r i o r s u r f a c e s of

tiie v e s s e l i n t h e l o v e r regions, The upper r e g . o n showed i n t e r g r s r i u l a r a t t a c k

A t y p i c a l c r o s s s e c t i o n of -the i n t e r i o r wall of t h e C W trap i s shorn i n Fig. 81. Comparison of t h e c o r r o s i v e a t t a c k on t h e I n c o n e l CRP trap and t h e Inconel o n l y on t h e vessel's i n t e r i o r w a l l .

bench-scale f l u o r i n a t o r described In Section. 1x1 i n d i c a t e d maxi mim r a t e I.osses Tor t h e t r a p t o be approximately twice t h a t f o r t h e bench-sca,le f l u o r i n a t i o n

vessel.

The most similar areas w i t h respect t o operaking envirormlents were

t h e lower vapor r e g i o n o f t h e f l u o r i n a t o r and -the lower r e g i o n of t h e CIW t r a p .

A t those locations,

s i m i l a r temperatures (app-r.ox 500째C) and.process gases

(F2,UF4) were p r e s e n t .

In add.i.ti.oa., however, sod.ium P l i i o r i d.e p e l l e t s were

i n c o n t a c t with t h e w a l l of t h e CRP trap.

The maxiuium bulk me-La1 losses i n

3: I (Trap:Fl.uorinator) while thF: ma.ximini i n t e r i o r i n t e r g r a n u l a r p e n e t r a t i o n ra-tio w a s > 5: 1. '%"iese d i f f e r e n c e s are

t h e two r e g i o n s were i n a r a t i o of

di.f-i^icirlt t o r e c o n c i l e i n view o f t h e 2:l r a t t o f o r f l u o r i n e c o n t a c t -time a t

e l e v a t e d temperatures f o r t h e t w o v e s s e l s .

No a p p r o p r f a t e reason can be advanced t o explain t h e v a r i a t t o n s c i t e d i n c o r r o s i v e behavior for. t h e C W trap and t h e 1nctc:)nel bench-scale flu.orinakor.

Howevex-, t h e r e s u . l t s p r e s e n t a d . d i t 1o n a l e - v i d e n c e t h a t I n c o m l should he used w i t h c a u t i o n as t h e c o n s t r u c t i o n material for eer2;ai.n f l u o r i d e v o l a t i l i t y p r o c e s s components.

Waste- Salt Line %he rFmova1 of waste f l u o r i d e s a l t from t h e VPP f l u o r i n z t i o n v p s s e l s was

acconlpli shed b y pi-essure t r a n s f e r through a Preeze valve anti waste-salt l i n e


T&le =I. Sutrxnary o f Corrosion Losses on Speclrnens TrepnrAed fron t i l e Inconel CTP Trap

Wall

3:i s-Lance Prom

SpeciTop Flange Weld Den Loca-Lion (in. !

,

T-T M-T

Top

Middle Bottom

B-T

3 8.5 26

Thi cline s s

2 ;

Losses" (mils) Maximum Minimurr. 7

-

24

I n t er g - a m l a r Pene r a t i o$0 (ni1s ) Interior Exterior Surf ace Surface

0

-

9

3 11 11

a

Total

MEX i num Corrosion

Losses (nils)

Maxi m ~ m Corrosio;.! RateC

(mils/br)

1c

O.i

3

-

11

46

0.46

None -

-

Based on 12 nicrcmeter neasurements takeE on each specinen arid s u b t r a c t e d Prom nomirial thickrless of 258 mils.

original

bAs determined by o p t i c a l xiicroscopy. c

,

Based on f l u o r i n e exposare time a t o p e r a t i n g temperature.

1

r

cn 0


- 161 -

Fig. 81”. Typical Microstructure of Sample B-T from t h e Interior Wall of t h e Inconel C’RP Trap Showing Intergranular Attack. E-tchant: Hydrochlori.e- ni t r i c acid . lOOX

.


- 162 i n t o a low-carbon steel waste c o n t a i n e r .

-

P r e s s u r e s oC approx 5 p s i & i n t h e

f l u o r i n a t o r were normall? uscd to s t a r t t h e waste-salt flow.

floT.red through ihe u a s t e l i n e bj sip~nonci'fect (See F i g . 79). r e p o r t e d here was used during tlie VPP L r i m s 1 - 4 and f o r t h e end of R i m M-&. The s u b j e c t w a s t e - s a l t l i n e

WRY

3/8-in.

3.

'irhe

s a l t then

The salt l i n e

siiicle transycr a t

sclied-li0 Tnconel p i p .

The l i n ?

ua; h e l d a t temperatures of 550-835"C f o r approx 22*5 h r and exposed t o â&#x201A;ŹlowLni; molteri salts f o r aboui 2 . 5 h r d u r i n 2 irir _rressbr.e t r a n 4 e i - s 52

It w a s

probable t h a t r e s i d u a l sal.1,s remained i n s t a t i c contac i with t h e i n t e r i o r xiall of t h e p i p i n g f o r a l l o p e r a t i o n s . A f t e r Run

M-64, t m p i p i n g

was rrrncjved from t h e p i 1 o t p l a n t ,

i n n i n e p l a c e s and specimens s e n t t o RMP r o r c o r r o s i o n a n a l y s e s . shows

2

sectioned F i g ~ i r c82

s c l i ~ n i s t i cdrawing of t h e w a s t e l i n t . ana t h e l o c a i i o i i of tile specinTens,

Table XXll l i s t s t h e c o r r o s i o n d a t a ~ s i a b l -shed i a t BMi by micrometer mea:x re-

i l e n t s and m e t a l l o ~ r a p ' nci exaurinations.

Maximum wal i t h i c k n e s s l o s s e s of

2 1 mils were found i n s p e c i ~ ~ IX e ~ which i w a s at, tlie e x i t end of t,he w a s t e - s a l t

line.

Metallographic examination o f tlie specimen7s snowed sli [;ht in'iergranular

a t t a c k oi" l / P - . m i l

p e n e t r a t i o n depth had occurred on t h e i n t e r i o r wall of a31

t h e sample; w i t h t h e e x c e p t i o n of specimen 1X.

i n t h e lat,Ler, a 3.5-mil t i l i c k

c o r r o s i o n product l a y e r vas found on the i n t e j - i o r surl"8C.e oP t h c npecirnen. Figure 8 3 shows t h e c o r r o s i o n prooiict l a y e r and t h e subsurl"al.e s t r u c t u r e .

The product layel, w a s spongy i n c h a r a c t e r and s i m i l a r i n appearance t o s u r f a c e l a y e r s found on s c c t i o n s removed from e s r l y t e s t Jnconel fre?/,e valve; which (5C?--l'6--hm o l ? %) a t 650°C. ( r e f 53)

hat3 been i n c o n t e c t w i t h NaF, ZrF]+, W4

Personnel a-i, 3811 suggested i h a t t h e pi-oduct l a y e r might be the r e s u l t o f s e l e c t i v e l e a c h i n g of chrolnium by t h e fuse4 s a l t .

They i n d i c a t e d t h a t til?

appearance was q u i t e s i m i l a r t o l a y p r s Iound on Jnconel i n corttact w t h hydrogen f l u o r i d e and f u s e d fluoride s a l t ? where chromiuni l e a c h i n g had been pl-oven.

Analyses or" t h e metall ' c spongy d e p o s i t found on s e c t i o n s Penloved from Lie i n c o n e l f r e e z e valve rerereficed above indica1,rtl consi de rable l o s s e s or' cnromium

'jL. R. T r o t t e r a n d H. E. Hoffyan, P r o g r e s s Repori on Vol.at,ility P i l o t P l a n t Corrosion .-___~.-.^. I'roblems t o A p r i l ? l J lq>r(, ORiUL-21!95, pp. 14-11, (Sept. 30,

1956).


n

I

UNCLPISSIFIED ORNL- LR- DWG 56057

TO F R E E Z E VALVE FROM FLUORINATOR

2,.51 1 G/

Y

24 in.

"/B -in.

SCHED 40 PIPE

ROTATE 9 0 d e g

SE

I

I

NOTE: D I M E N S I O N S A R E IN INCHES

ROMAN N U M E R A L S INDICATE L O C A T I O N OF SPECIMENS R E M O V E D FOR C O R R O S I O N A N A L Y S E S

W A S T E -SALT CON TA I N E R

Fig. 32. Schematic Waving oI" Inconel Waste S t l i t Line fron WP Fluorinator. Roman numerals indicate location of specinens removed Prom i i n e f o r corrosion analyses.


XXTI. Corrosion Loss Data ror Waste-Salt JLne

'Yah1.e

Material:

Spec i men

scned-40 Inconel pipe

?/%in.

Distance from Top o f I.Ja s Le-Salt Contai n e r (ill.)

Wall

Thic k m s s

~ossesa ( m i Is )

In&rg:ranular

Penctrailon (Interior Surfacc)b (mils)

I

2

TI1

'I'otal CorrosionC (mj7 s)

6

I1

2 2

8 6

IV

1

>

1.

l+

1

4

L

V

7.1 40.5 39.5

VT

VI:I:

VI11

LX

......... .........

3 3

6

a

......... ..................

1

21

0 .. ..............

5

1

I

0 .......-..-___........-.

21 -I

BE sed on metallographic meas1-1rcmel i t s at i (3. s u b t r a c t 2 d f'rorn nominal original. wa1.L thickness of 91 mils. b No intergran1;Aar a t t a c k vas observed on the o u t e r surrace of the pipe. C

Total. cori=osior, cqua1.s the assumed. o i - i ~ g i n a l-tlii.ckness of 91 m i l s minus

t h e measiired sound ineta.1. remaining.


-

165

-

Uncla s s j.fie d BMI C623

Fig. 83. Microstructure of Sample IK from the Interior Wall of Inconel Waste S u i t Showing Corrosion Product Layer.


solution

â&#x201A;ŹTom t h e a l l o y . 55 The moisture

Absorber Gas-Di.stribi;.t-i.on Ring Fai hre. ....._ lll__l^-

~

The Incoiiel g a s - d i s - t r ~ b u t i o n

r i n g i.n ille 13 r s t ah:;orber i'ai 1 . ~ ~d1u r i n g VTP operai;ions.

The faili;.re was

discovereci a f t e r Run W-32 but i s b e l i e v e d t o have occurred d u r i n g Run

M-47.

A schemai;i.c vi.ew of t k absorber- and t h e gas-d-i c t r i b u t i o n r i n g I s sh.owi in F j g . 64. As showil O i l t h e photographs, F i g . 85-a ami. -b, approx 3 i n . 3 oi' I n c o n e l wzs mel-Led i n R K z r e a roughly 180 dei; lrom t h e junc~Lionoâ&#x201A;Ź -ilie (lis-

t r i . b u t i o n ring and t h e i n l e t p i p e -

T-:ie melted. area w a s about

t h e d i s h 5 b u t i o n r i n g w a s ncar1.y severed by thi.s actTon.

The fused s a l t v i s i b l e fn F i g .

65-b around

5 in.

l o n g and

t h e metal nodules whi.ch were

formed as a result oP m e l t i n g was found by aiial.yscs t o c o n t a i n

4 w t $ Cr

as

CrF,, 10 wt $ N i as NiF2, aiid 3 ~d$ U as UFIL. Process chemicals normal.1.y 3

55F. F. Blankenship, ~ The-Effect o s.-i o n OC Nickel - - - of - S t r o n g O x i d ~..a. ..n..t son C o r r_.__. A l l o y s by -. F1uoY.i r k Melts, C F C O 3 ~ ~ 30, r c ~ 1 . 9 6 0 ) . ..... I-

_ I

- l

"R.

Fluoride P. Mi-lford, ____I_^__.__. E n g i n e e r i n. g Uesi.gn .......... Fea1;ui-es of...._ t..h ._e O R J K -_ r--. P i l o t P l a n t , CF'--5j-JL-l8, pp. F J G .

...._ Vol.ai;ili_ty

~

I _ g


1

THERMOWELLS -.

UNCLASS lFlED ORNL-LR-DWG 49172

/GAS

EXIT

/,GAS INLET

c

DISTRIBUTION R

FAILED REGION IN DISTRIBUTION RING--

T

F i g . 84. Schemat-ic View of WP Inconel Absorber and Gas-Distribution Ring Illustrating Area o r Failure.


- 168 Unc].as 8 if?.e d

Y-2323k

I

, :1

\

Unclassified

Y-23295

F i g . 85. Photographs of F a i l e d Region from the Inconel Gas-DLstxibution R i n g o f Absorber, (a) Top V i e w (b) Hottom V i e w , Showing Molten and Recast Nodules and Adhering S a l t .


p r e s e n t i n this a r e a of t h e absorber were NaF p e l l e t s , F ant1 UF 2 6' Table XXIIL shows the pri.oi- h i s t o y y of the r i n g up to t h e - t i m e of f a i l i n e . Three unusual

p l a n t o p e r a t i n g procedures werz a p a r t of t1ij.s prior h i s t o r y :

"7

(1) substitii-

t i o i i or hyd-rogen f l u o r i d e f o r l o w teniperature f l u o r i n e conditioning, ( 2 ) allowing

fluorine t o e n t e r t h e absorber a t approx 600°C m t h e r than 375°C as speciYieci. i n the standard operati-ng procedures

(the h i g h e r temperature was used t o

iniiiiuiize hy-drogen f l u o r i d e €rom the KaF and t o reduce t h e sodium f l u o s i l i c a t e coritent of t h e NaF), ( 3 ) use of an a c c e l e r a t e d coolirig r a t e a f t e r desorptiion. Orily ( 2 ) is felt t o be p e r t i n e n t toward. ca1xsin.g t h e f a i l u r e d e s c r i b e d .

Metallographic exanination and. cherni-csl analysis of the samples c u t f r o m

t h e f a i l e d pipe, revealed only tha-L the Inconel w a s norrflal i n chemistry and.

microstructure.

The microstructure w a s equivalent t o a s - r e

molten and r e c a s t nodules exhibi.Led a typical cast s t r u c t u r e .

ived stock.

The

The Iriconel g a s - d i s t r i b u ~ ; i o nring appears t o have i a i l e d as t h e r e s u l t

o r i g n i - t i o n with f l u o r i n e .

Igni.tion i s b e l i e v e d to have been Lnri.tiated by an

unlinown f o r e i g n substance, such as di.rt o r grease, introduced while t h e absorber

was open.

The :r"aili.ire porints up the n e c e s s i t y f o r extreme c l e a n l i n e s s when

hand.1.f ng f l u o r i n e .

Inspecti-onof Absorbers

e

Following fl.!iorj.rial;ion Iiun

1,-9, the absorbers

.

were visumlly i n s p e c t e d and t h i c k n e s s measurements t s k e n w i tii a"Vidigage ''

The ultrasonric device was operated by members of the Nondestructive Testing Group of t h e Metalliirgy Division.

R e s u l t s of those examinations are c i t e d i n

Figs. 136 and 8'7. %'ne maximu.m det(i?ctible l o s s e s found iwere Rpprox 30 mj.ls i.n t h e upper r e g i o n s of t h e vessel, a r a t e of approx i-'luori.ne r e s ? dence tiaici..

0.06

mils/lrr., based upon

Based on -Lhese r e s u l t s , it i s believed t h a t t h e v e s s e l s c a n continue t o

be used I n pi.lot plant o p e r a t i o n .

"F. I.J. Miles and W. 1-1. C a r l - , Engineerin:: Evaluation of V o l a t i l i t y P i l o t P l a n t Equipnlent, CF-60-7-55 (September 30, 1560) pp. 95-96.

P


- 1.70 -

Table XXTLi.

1.

Fxposii re Hi:>torj f o r Absorber C o n t b i n i n g Failed I n c o n e l Gas - Dist r i b u t i o n Ri.ng f roni Fyb c o rber FV- 120

Twelve ( 1 2 ) a ~ ~ o r p t i o n - d e s o r - , t i o nruns u s i n g NaF which t y p i c a l l y iric luded:

a.

Absorption a t

UF6 + 3 N a F

6 k 1 5 0 " c ; 2 hr F2 at, 15 staridard lit,ers/min > UF6- 3 N a F

-

at 20 s t a n d a r d l i t e r s / m i n ror 1 . 5 h r

b.

kLrge-zparge w i i h N

c.

J k s o r p t i o n ai, l O O - l + 2 5 " C ;

2

F2 ai UF62.

3.

12-14 hr

- 18

3 NaF

I+

standard liters/min

> UF6 NaF Vessel w a s remove0 f r o i ~ is e r v i c e and l e f i exposed w h i l e t h e remaind-er of t h e sysiem was ua1,er washea, a r i e d , and t r e a t e d w i t h Fp. V e s s e l w a s theri p l a c e d hack i n s e r v i c e . One (1) s p e c i a l run whose purpose w a s p r e p a r a t , i o n of Map from N ~ K F , .

a.

Purge-sparge with It

at 2

-3

s t a n d a r d l i i e r s l m i n Tor 12 hr

-

2 k l P 5 " C i n 7 hr a t 125째C for 5 h r

b.

Preparation of N a F under N NaHF2 + A

NaF

<-

I -

I

a t 3 s t a n d a r d l i t e r s / m i n by

2'1 I F

125-600째C i n a t 600째C f o r

c.

at

x-

- 15

C o n d i t i o n j n g of a b s o r b e r at

9 hr

4 hr

X

635째C w i t h F2

standard liters/min ror 0.5 h r

Fail-ure i s t h o u g h t t o have o c c u r r e d ai, this t i m e .

~~

.

.


FV-120 FlRST ABSORBER Materiol:

UNCLASSIFIED

O R N L - L R - D W G 49j73 GAS mil. E T

- ) in. Inconel, rolled p l a t e - in. Inconel, flat p l a t e

Shells Bottom

GAS EXIT

TiiEHMOWEI i.s

Service Conditions: "-5000 hr -400 hr -310 k g <0.1 in. H,O

NaF contoct

UF,

contact

Pressure Absorption

Wall temperature F, contact

-

5

psig

-

45-150°C 100 hr 100,000 std. liters

-i

Desorption

100-425OC occasional excursion to 6C.O"C F, contact -400 hr ".170,000 std.

Wall temperature

NaF P E L L E T BED LEVEL----

FRONT VIDIGAGE READINGS TAKEN ALONG THIS LINE

liters

Visual Inspection

Dl STRl BUTICIN RINr .- .........

interior

2 -

Covered with an adherent yellow-brown deposit except for the surfaces within 3 in. o f the botfom. No defects visible. No coating or defects visible. A l l bead3 v i s i b l e appeored to be i n good condition.

She1 I Bottom Welds Erterioi

Shell -- Covered w i t h a thin black adherent film, presumably oxide. Dottorn - Covered with a thin block adherent film, presumably oxide. Welds - A l l bends nppeated to be i n good condition. Yidiyoge Inspectian:

-

Distance'

.......

2

L o c u t i o n Remarks

Neck

5

Reducer

She1I She1 I Shell Shsl I Shell She1 I Shell She1I She1I

8

10 12 15

2o

23 25 28

in front

and

Wall Thickness i n Inches

...

I_--.....

Girth-! Weld

(Nondestructive Test Section o p e r o b r s expressed "no confidence" back readings due to hie w a l l deposit onrl operotional difficulties.)

Front

Series

0.226 0.222 0.236 0.223 0.230 0,235 0.240 0.238 0.241 0.242 0.244

Rack

Series'

0.235 0.220 0.224 NA NA NA NA 0.235 0.238 0.240 0.234

....

Bottom

.....................

Sries3

_-___ O. 370 0.374 0.370

.......................

1. In inches, dram bottom of flanae. 2. These readings token 180" from front series. 3. Random readings, +0.002 in. NA: Not Available

Fig. Ab sorbe i-

.

86. R e s u l t s

o€' V i b u e l and Vidigaije I n s p e c t i o n on

VPP F i r s t


-

172

-

FV-121 SECOND ABS3RBEW Material:

GAS INLET

\ in. Inconel, r o l l e d p l a t e

Shells -

-

Bottom

UNCLASSIFIED O R N L - L R - D W G 49174

I-HERMOWkLt-S

GAS EXIT

i n . Inconel, f l a t p l a t e

-r

Service Conditions:

-3000 hr -2.50 hr -200 k g <0.1 in. H,O

N a F contact UF, contact Pressure

L

NoF P E L L E T

I t

- 5 psig

Absorption

Wall temperature

F,

contact

65-15O"C - 4 0 hr -36.000 std.

F R O N T VlDlGAGE R t A O I N G S TAKEN ALONG THIS LINE

liters

Desorption Wall temperature

100--425"C 600째C

occosionol excursion to

F,

-250 hr -90,000

contact

std. l i t e r s

DISTRIBUTION RING

V i s u a l Inspectian Interior Shell

- Covered

with

ail

adherent yellow-browit

deposit

except for the vessel neck and surfaces w i t h i n that noted for

Bottom Welds

6

in.

T h e deposit appeared thinner than

o f t h e battoin.

FV-120.

No defects visible.

- No coating or defects v i s i b l e . - A l l beads v i s i b l e appeared t o

be i n good condition.

Exterior

Shell

-- Covered w i t h a t h i n black adherent film, presu,ilably oxide. Bottom - Covered w i t h a thin black adherent film, presumably oxide.

Welds

-

All

beads appeared t o be i n good condition.

Vidigage Inspection:

-Distance'

2 5

a

10 12 15 Girth 2' Weld

2o

23 25 28

(Nondestructive Test Section operators expressed "no confidence" back readings due to wall deposit and operational d i f f i c u l t i e s . )

....................

Wall Thickness i n Inches

L-ocution Neck Reduc:e; Shell She1 I She1I Shell Shell

Shell She1I Shell Shell

1. 2. 3.

i n front and

....,.

~

~

-

....... ......... ..... ~

Front Series

Back Series?

Bo ttoiii Sari es

0.228 0.222 0.220 0.222 NA NA NA NA 0.228 0.232 0.238

0.232 0.230 0.230 0.230 0.228 0.223 0.226 0.230 0.237 0.240 0.238

0.370 0.374 0.372

In inches, from bottom o f flange. These readings token 180Ofrorn fiont series Random readings,

NA: Not

i0.002.

Available

F ~ E 07. . Results of V i s m l and Vidigage Inspection on VPP Sccond Absorber.


Valves and. F i t-_-tings

_II___.___)

Aside -from sporad.ic leakage a:nd.

S I ) p ~lugL ~mg

of valves c a r r y i n g UFG, valves sncl Y.i. t;i;ings

j.;o

by unideiz-i;.i.fied depooi Z;s

t h e WP performerl s a t i s f a c -

-torri.l,y.57 Mariy screwed f i t - k - i n g s c a r r y i n g n i t r o g e n were back-welded a f t e r

various ammints of p l a n t o p e r a l i o n a l tri.me t o el.i.mi.nate such l e a k a g e , Pl.imri.ne carq-i..ng valves of.'various body iiiateritzls,

IIicoi-.el, s-t:tel, types

316 and 347

i .e

~

, Monel,

ntckel,

s t s i n l e s s steel, b r a s s 7 and copper, were

G-ra7,ed. i n t o the a s s o c i a t e d piping.

At ternperaturea greater t h a n

welded.

01-

I,50째C,

0nl.y n i c k e l and Inconel valves were i n contact With Yl.uOr?.ile under

riijrm.al operatirig condjitionr..

0:m ra:;.l.ure, ol*igi;inal.ly tho11glit to be in a

valve 'out later discovered

to be 1n t h e adjacent, f i . t t i n g s , has been sel-ected for treat;nient here beca.use of tlie mn-Lerials involved and t h e i r reaction -to ser.'ifice c o n d i t i o n s .

.Ti"oI.Lowi.ngRun L-J.I. In tile VPP, leaded, yellow 'orass valve fittings of tile

coiiiposi t,i.on 60-63$ CL~-2

5-3.7$

o t ' h e ~ ? ~ aZn , l . (vendor ' s

Max Fc+O.5$

Pb--O.3$

nxislysis) were rmoved Prow a ni trrogen piirge l.i.ne, p E - 3 1 ~because ~ o f defective

Valve opera-tioil" The i.:nJ..et

side of the valve, a pnckless di.qhragm-sea1 valve with am

Inconel diaphragm, J h r a r i i c k e l skem p o i n t , a a d . Mon?3. body miJ. tr:im,

T,T~:;

placed

i n conjunction with -the Nay absorber outlet p i p i n g which c a r r i e d F, and. I F

Unde-r

gases,

6.

2

1:to:rinal

operat 7.ng conditions, t?-eval.ve wa:; not in contac-t wi-t'ri p r o c e s s

b u t there was cori.iiiiuous xi trogeri coi7tact.

Weti nl.tj-ogen pressixe

T

~

"he valve was sb.u.i only

low S am% there w a s the p o s s I . b i l i t y of process gases

diLCPusing p a s t the valve t o the i.nstnunentatinn iiaits

~

1hri.ng the e a r l y L-iluiis, p e r s i s t e n t sysi;en: pl.iigs and low pressure i n Lhe

n-itrogen l i i i c pmbably peri1ij:Lted

F,

,..

md W

f?i t t i i i g s :i?o:t* an unkno-wii p e r i o d o f t i m e

v z l v e anz. i t s fi-1;1; i rigs i m s appmx

I

6 weeks

6 io

c o n t a c t the valve and its

The operaking se:r-vicc: time on t,be ~

Visual examination o f -LA? valve d i s c l a s e d n o obvi.ous d e f e c t s .

i t :fa::;siili),jected t o severml tifries cperating pressure

(15 pslg)

ne1 and fouiid tc:) f i m e t i o n s:2:;7'.~-1"ai",'~,cwi-tha-1.1 )~ri..~y1; k a k a g e .

T'nerefore,

by VPP per~on-

Tile v a l v e m,s

scbseyu.errthy placed i n s tack. t o be u s e d e s an entlzrgency yeplacement


Vrsual- o b s e r v a t i o n of t h e Ti-i-Lings r e v e a l e d t h a t several- components ha? r u p t u r e s F i n n i n g i h e cofflpkte l e n g t h of the wal I s .

The fiss:clres were normal.

t o s t r e s s e s induced d u r i n g iiis’ial.l.ati_cin. FTgi-i=e 88 and Tab1.e XXLV show and d e s c r i b e t h e d e f e c t s noted.

Metal1.ograplii.c examination oi’ -the fi~tA,inp;s r e -

v e a l e d t h e cracks ’io be i n t e r g r a n u l a r i n n a t u r e .

Dezinc iiicati’.on apparent1y

occurrea a l o n g t h e i n s i d e edges oi” t h e f i s s u r e s , as evi deiiced by copper-ric’n deposits which l.i.ned t h e € i s s u r e s . (See Fig,

89.) Copper deposits were slso

e v i d e n t i.n s e v e r a l g r a i n b o u n d a r i e s rad.i.atin,g outward froa i:ie

Y’l-aw.

c o r r o s i v e a t - h c k w a s n o t e d on t h e o u t s i d e of t h e i n i . e t imton, Fig. A i t h o i i g h all. evidence i n d i c a t e s ’chat f a i l u r e was by selectiv:,

General

00. i li<A?j3--

g r a n u l a r d e z i n c i f i c a i t o n , t h e s t r e s s e s indLced d u r i n s i..nsi;al..l.ation were believed

to have provided. a s t r o n g d i r e c t i o n a l d r i v i n g force.

‘illie use o f stock Mone1

f i - t t i n g s , because of i t s iiicreased c o r r o s i o n r e s i s t a n c e , was recommended for

use i n the enviromient d e s c r i b e 6 .

The a s s o c i a t e d Monel v a l v e was found t o be i_n good o p e r z t i n g contii-tion,

appeared s a t i s f a c t , o r y , an.d can c o i ~ t i n i i et o be used f o r the merit i.oried s e r v i c e conditions.

‘This fail.ii.re s e r v e s t o yoini; o u t the n e c e s s i - t y f o r consta.o.t v i g i l a n c e i n s e l e c t i n g m a t e r i d s and components f o r a h i g h l y c o r r o s i v e p r o c e s s scheme. T h i s i n c l u d e s t h e s e l e c t i o n of p i p i n g a n d . j o i n i n g cou.pl.es which should, i f at

a l l p o s s i b l e , match t h e cotniponeilts i n c o r ~ - o s i o n - r e s i s t a n tp r o p e r t i e s . F l u o r i n e D i s p o s a l System

Excess f l u o r i n e an& ni-trogen from t h e VPP have been d i s p o s e d of by co-

c u r r e n t c o n t a c - i w i t h a n aqueous KOH solu-tioii

F i g s , 79 and 91.)

iil

a gas-disposal u n i t .

The KOH s o l i l t i o n w a s p r e p a r e d i n a c a u s - t i c surge tank,

shown i n F i g s . ‘79 and 92, t o a c o n c e n t r a t i o n of 2--lO$

disposal. unit.

(see

KOH and pumped t o

the

The c a u s t i c s o l u t i o n w a s t h e n sprayed i n t o t h e d i s p o s a l u n i t

as t h e e x c e s s process g a s e s e n t e r e d t h e vessel.

F l u o r i n e i n t h e waste g a s e s

fomied potassium f l u o r i d e i n water solution accord.i~ngt o


c

-.

rn

a h

p1

B

0 rl

rl

e,

rack not shown i n photo)

Outlet Nut

Outlet Front Ferrule

Ferrule

Outlet Back

Ferrule

Nut

I n l e t Front Fersule

â&#x20AC;&#x2122;

a

d

!I

rn

(d

k

6

rl

* Inlet

cl .d

d

5I I n l e t Union

1.75

m

-

1


- 176 Table XXIV.

-

Defects Found i n Leaded Yellow Brass F i t t i n g s Subjected t o F and u!?6

2

P a r t Name

Location

Defect

*

Union

I n l e t s i d e of valve

W a l l f r a c t u r e through threaded end covered by hex nut. Fracture extended through hex body and p a r t of opposite threaded end.

Hex Nut

I n l e t s i d e of valve

W a l l fracture ferrule.

Front F e r r u l e

I n l e t s i d e of valve

W a l l fracture ferrule.

Back F e r r u l e

I n l e t s i d e of valve

Crack

Union

*All

Fig. 88).

* *

running e n t i r e l e n g t h of running e n t i r e l e n g t h of

* partially

through w a l l .

W a l l f r a c t u r e p a r t i a l l y through threaded end covered by hex nut. (Not shown i n Fig. 88 because o f photo o r i e n t a t i o n . )

f r a c t u r e s and cracks were e s s e n t i a l l y i n l i n e with one another (see


- l.77 -

c


Fig, 90. VPP Leaded, Y e l l o w Brass T n l e t Uiiion Showing Ceneral Corrosive E t c h a n t : NH40H-H 0 -R, 0. 1OOX. 2 2 2

Attack.


- 179 UNCL.ASSlF8 ED G R h I I ~ - l A - O W G 49175

FV-150 DISPOSAL U N I T

GAS Material:

Shells

-

~ n hlonel, . diad sheet

Heads --

in. Idonel, flanged o i d dished

Serrice Conditions:

Excess F, with N, froln ptocesal~;gpassed w t h 2-10% KOti ~n tower ot 0.5 c f m a concentrotion of 2% KOH, 5-15?, KF.

co-current c o w

I"

toct

Dircl-torged ot

""5000 I,(. -8000 hr

Clrculating Not cii:ulating

35-55'C o c c ~ s ~ o n oc1x c u r s i o n ~to IOO'C 0.1 in. i1,O

Temperature Pressure Virrrol Inspection Interior

F

C o u l d not be inspected at t l i i s time. Exterior

Shell

- Covered w i t h sn adherent green deposit. VI S I bl

K O r i INLET TOTAL

OF

SIX

N07ZLES. 1 5 - 1 n OC

No ,defects

e. Covered w t h on adherent green deposit. fects visible. Welds - A l l oppeored to be i n good condition.

Heed -

..

I '7

No de-

Vidigoge Inspection

...................

Distance'

Stl FL. .L

C!rcumferentiil Series'

~

Series

I

0.119

0.118

N o 1--2

9

0.124 0.126

0.125

0.127

0.118 0.11R

0.125 24

39 54

0.118 0.119

0.125

0.125

0 130 0.129 0.178

0.125

0 125 0.127

0.126

0.130 0.129 0.127

0.126 0.128

0 127

0.130

0.127

67

0.127 0.129 0 I29

a4

0.128 0.129 0.120

0.128 0.128

0.150

0.128

99

I.

Wall Thickness i n Inches' ~.~...~...~ ............................. SHEI. L SHELL HEAD Inter-KOH N o z z l e F, Inlet-Impingement series

0.I29

0.125 0.126 0 127

No. 2 - 3 0.128

0.128 0.126

No.

3-4

0.124

0.128

Ser i e I 3

0.126 0.125 0.127 0.126 0.127 0.127 0.128

0.128

0.123 0.128

0.128 0.129

Dished Top

0.182 0.184

0.184 0.186 0.183 0.182 Flanged Side

0.185 0.184 0.189

0.190 0.189 0.186

No. 4--5 0.129

0.128

No. 5-6

0.124 0.125

0.129

Dirtonce, v e r t i c a l l y down, i n inches storting U I top liead to shell weld - - reference only to shell

c l i c u m f w m t i o l Femes. Peodings taken ot O O a m

-

120", mtoted 20' for each S U C L ~ S S I Ygroup. ~ 3. Readings at 1 in. tntewnlP starting 13 in. below the liead to shell weld 180" from F 2 Inlet. 4. A l l reodings, +0.002 in.

2.

Fig. 91. R e s u l t s of Visual and Vidigage I n s p e c t i o n on VPP Gas Disposal Unit.


UNCLASSIFIED ORNL-LR-3WG 49476

VIDIGAGE R E A D i N G S T A K E h ALONG :HESE IIXES

Materiol:

Shells beodr

-

%,,:n.

J

@,onel, rolled sheei

\

FROkT

in. Monei, ::anged and d:rhed

RACK

Service Conditions: Continually &-b2 full o i 2-10s KOH with present. (One area sublec: to agitation) Circulating Not circulating Temperature Pressure

-5000 -8000

F-

hr hr

25-55OC Atmospheric

Visual Inspection

Interior Could not be inspected

01

t h i s time.

Exterior Shel:

- One end covered

361n

wtth an odllerent green deposit. N o defects noted.

Heads - Both heads covered with an adherent green deparlt. Welds A l l beads appeored to be tn good condition.

-

-

_1

No defects ncted.

24 i n

94 i n

Vidigage Insection

WELDS

P

LLU

Wall Thickness in Inches? ~

DI stance'

Front Serb er

Remarks

0.195 0.196

3.190

3.188

10 14 13 22

0.187

0.187/ 0.190-

26 30 34

Longi tvdi na: w e l d here

ci. I W

Bottom

i.

2.

Remarks

0. I94

3. :a9

TO?

Bock Series

/ weld h e r e

Longi tu61no1

0.196 0.195 0.195 0.194 5.194

Distance, I n inches, circumferentiolly from top of sheii. A l l readings, ?C..002 1 2 .

FV-152

SURGE TANK

Fig. 92. Results o f Vlsual End Viaigage Inspection on V?? Surge Tank.

~

3


- 181 -


1

i : -

I

-%

I I

\

I

-.

i

I

Unclassified Y-32029

, /

*" I

.

\

h,

~ i g .93. cross S e c t i o n s of Gas i)isposal Unit I n l e t Pipe ( 8 ) ~hotomacrograph ShowFng Severe P i t t i n g Attack. 15X. ( b ) P o r t i o n of F i g . 9 3 showtng t y p i c a l surface a t base of p i t . 5OOX, Etchant: Acctie-nitrlc-jriydrs@hlortc acid.


- 183

-

The formation of hydrogen fluoride seems p o s s i b l e

from t h e I-eacLions of

fluorine rnonoxi.de or f l u o r i n e with t h e u v a i l s ? d l e :*rater of solutio?:! p r e s e n t

~

Iiivestigatxors have reported the h y d r o l y s i s r e a c t i o n of F,0

F20

f

H20

>

o2

2

-c 2 m

to be very slow a t o r d i n a r y t e m p c r s t u r e c '0u.t a steam-E',O r e a c t i o n occurs so


- 184

-

hydrogen f l u o r i d e c o r r o s i o n h i g h l y a c c e l e r a t e d by t h e p r e s e n c e or oxygeri. Al.so,

a t p a r t i c u . l a i - c o n c e n t r a t i o n s o f hyarogen f L n o r i d e i n watzr, cl-ose t o

t h e a z e o t r o p i c composition

rates on Monel of

(33

145 m i l s / y r

wi;

$),

one i n v a s t L s a t o r has r e p o r t e d c o - r r o s i o n

a t I.2O"C. 'ref

6 ' )

It niay be tlisi; e i . t h e r or

b o t h oâ&#x201A;Ź t h e s e r e a c t i o n s may be r e s p o n s i b l e f o r t h z 1ocal.i x e d a t t a c k d e s c r i b e d . C o n s l d c r i n g -{;'neeasy replacement of t h e gas-in1.e-i; n o z z l e and the major

c o r r o s i o n problems remai.Iiing t o be s o l v e d i n t h e VPP, no development w c r l i

has been p l a n n e d toward :finding an. impi-oved r n h L e r i a l or const,mcti.on.

Prrocess G a s Lines S e c t i o n s of Monel p i p e a n d copper t u b i n g n e a r t h e

VPP a b s o r b e r s , cherni-

ea1 traps, and c o l d t r a p s were removed from t h e process gas p'iping s y s t e m

M-64 and

a-fteT Run

s e n t t o BMI for c o r r o s i o n anslyses, A schematic drawing

shoT,rLng the l o c a t i o n 01 -these s e c t i o n s i s preserited. i.n F i g .

94, and a &scrip-

'tioil o f t h e p i p i n g and t h e i.naividual. p r o c e s s environments can be found i n Table X X V .

The w a l l t h i c k n e s s e s of t h e s e c t i o n s w-ere measured b y BMI and no i-ndica-

Lion o f s i g n i f i c a t i t riietal l o s s e s were found.

The metallographi-c e x a m i n a t i o n s

conducted on t h e specimens d i s c l o s e d no s e r i o u s c o r r o s i v e a t t a c k .

A l m o s t all

of' t h e speci.mens showed i s o l a t e d p i t t i . n g b u t the pits were less tlmn one g r a i n d.eep.

S l i g h t i r i d i c a t i o n o f s e l e c t i v e a t t a c k a t t h e g r a i n bouridari e s was

o b s e r v e d on specfmens 1-1, 1-2, 1.-3, 2, and 3 which were l o c a t e d close t o the

a b s o r b e r s and t h e f i r s t c o l d t r a p , ,

However, t h e i n t e r g r a r i u l a r a t t a c k was

never' d e e p e r t h a n one g r a i n , and f o r t h e most p a r t , was l k s s t h a n 1 m i l deep.

6%.

Z. F r i e n d , "Nickel-Copper A l l o y s , 'l C o r r o s i o n Handbook ( e d , bj Sons, New York,-i91TE--Ll--

H. If. U h 1 i g ) p . 273, John Wiley and


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ORKL-2832 Metals, Ceramics, a n d Mzterials TID-1! 500 (l.6th c d I

614-68. 69.

'-7.0

71. 72.

'73.

:74. 75. 76. 77. '78. 79.

80. 81. 82. 83-85.

86. 8'7. 88. 89. 90.

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11.2 . A. H. Sne 11 113. s. 3. Staj-nker 114. J. A. Swarto u i 115. E. H. Ta yl-or 116. A. M. $72i n b e rg 117. M. E . Whatley 1.1.8. c . L. Whi h e r s h 119. C. E . Wj ntcrs

- 1.88 -

120.

E . L. Youngblood

123.

S. 11. Kocn:ig ( c o n s u l t a n t )

1.21. A . A . B u r r ( c o n s u l t a n t ) 122. J. L. Greg2 ( c o n s u l t a n t )

I?)!-. C. S. Smii;Ii ( c o n s u l . t a n t ) 1P5 P:. Srnol.inchowski ( c o n s u l t a n t )

126. E . E . StansIJury ( c o n s u l t e n - i ) 127. 11. A . W i l h e l r ( c o n s u l t a n t )

l?8. D. E. Baker, GE I I a n f o r d 129. 5. E . Bigel-ow, 4EC, OAL) 133-131. D. Cope, AEC, OK0 1.32. 0. E. ~w)-ex-, B r a 1-33 Ersel Eh-ans, GE HanPord 134. F . W. Fhk, R M I +

135. 136. 1.37. 138. 139.

s.

W. J. M. 140. R . l.)+l.

1 42. l.jL3-719.

Lawroski

, AI%C,

P. D. M i l l e r , B r a

S e e f e l d z , AI!L Simmons, AEC, Waslii.ngton J. Steindler, ANL K. S t e u n e n b e r g , ALrL D. K . Sl,eveins, AEC, Wzchington R . C . Vogel, Am Given dlstrri.huti.on as shown in TID-)I500 (16th ed.. ) under Metals, Ceramics, and Mzterials Ca.tegory (75 c o p i e s - 0â&#x20AC;?s)

ORNL-2832  

http://www.energyfromthorium.com/pdf/ORNL-2832.pdf

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