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Contract No. W-7405-eng-26

Reactor D i v i s i o n

EXPERIENCE W I T H SODIUM FLUOROBORATE CIRCULATION I N AN MSRE-SCALE FACILITY

A. N. Smith 0TI CE This report was prepared as a n account of work sponsored by the United States Government. Neither the United States nor the United States Atomic Energy Commission, nor any of their employees, nor any of their contractors, subcontractors, or their employees, makes any warranty, express or implied, or assumes any legal liability or responsibiiity for the accuracy, completeness or usefulnew of any information, apparatus product or process disclosed, or represents that its UP: would not infringe privately owned rights.

N- 1

SEPTEMBER 1972

NOTICE This document c o n t a i n s i n f o r m a t i o n of a p r e l i m i n a r y n a t u r e and was p r e p a r e d p r i m a r i l y f o r i n t e r n a l use a t t h e Oak Ridge N a t i o n a l Laboratory. It i s s u b j e c t t o r e v i s i o n or c o r r e c t i o n and t h e r e f o r e does not r e p r e s e n t a f i n a l r e p o r t .

OAK RIDGE NATIONAL LABORATORY O a k Ridge, Tennessee 37830 o p e r a t e d by UNION CARBIDE CORPORATION for the U.S. ATOMIC ENERGY COMMISSION

iii

CONTENTS Page .

........................................................ 1. INTRODUCTION ................................................ 2 . TEST OBJECTIVES ............................................. 3 . SUMMARY OF TEST RESULTS ..................................... 3.1 General ............................................... 3.2 Funping C h a r a c t e r i s t i c s ............................... 3.3 Control of t h e S a l t Composition .......................

ABSTRACT

3.4

C o n t r o l l e d Deposition of Corrosion Products

...................................... 3.6 Miscellaneous Observations ............................ 4 . DESCRIPTION OF TEST FACILITY ................................ 4.1 General ............................................... 4.2 S a l t Piping and Components ............................ 4.3 S a l t Sampling Device .................................. 4.4 Heating and C o n t r o l l e d V e n t i l a t i o n .................... 4.5 Gas System Design ..................................... 4.6 BF3 Disposal .......................................... 4.7 Instrument and Controls ............................... 5 . TEST PROCEDURES, OBSERVATIONS, AND CONCLUSIONS FOR THE PRINCIPAL TESTS ........................................... 5 . 1 Pumping C h a r a c t e r i s t i c s ............................... 5.2 Control of t h e S a l t Composition ....................... O f f - G a s System

5.3 5.4

Operation of t h e BF3 p a r t i a l p r e s s u r e c o n t r o l system

............................... 5 . 2 . 2 Methods f o r monitoring s a l t composition ........ 5 . 2 . 3 E v a l u a t i o n of t h e t h e r m a l c o n d u c t i v i t y method .. Corrosion Product D e p o s i t i o n .......................... O f f - G a s System Flow R e s t r i c t i o n s ...................... 5 . 4 . 1 Plugging e x p e r i e n c e ............................ 5h . 2 5.4.3 5.4.4

5 5 .

...........

3.5 Analysis and C o r r e c t i o n of R e s t r i c t i o n s on t h e

5.2.1

.................................. D i s c u s s i o n and e v a l u a t i o n of t e s t r e s u l t s ...... Off-gas tests

General conclusions from o f f -gas t e s t s

.........

6 6 7 7 â&#x20AC;&#x2DC;7 12

14 14 18 18 19 19 26

31. 36 40

48 53 54 56 71 77

6 . CHRONOLOGY. PERTINENT OBSERVATIONS. AND OTHER TESTS ......... 6 . 1 Chronology ............................................ 6.2

6.3 6.4 6.5 6.6 6.7 6.8 6.9 6.10

.............................. Pretreatment and T r a n s f e r of S a l t Charges ............. Freeze Valve Operation ................................ Eubbler Tube Operation ................................ Experience w i t h S a l t Level Instruments ................ Back D i f f u s i o n a t t h e Pump S h a f t ...................... A S a l t Leak t o t h e Atmosphere ......................... Experience w i t h Handling BF3 .......................... Corrosion Experience .................................. Analyses of S a l t Samples

............................................ 6.12 Valves i n BF3 S e r v i c e ................................. 7 . RECOMMENDATIONS FOR FURTHER DEVELOPMENT WORK ................ 6.11 Green S a l t

106

106 107 107 107 108

Corrosion Froduct Deposition

7.3 7.4 7.5 7.6 7.7 7.8

S a l t Level Instruments

................................ R e s t r i c t i o n s ...........................

Control of S a l t Coxposition

...........................

Intermixing of hlclten S a l t s

...........................

................................ EF3 Eiecycle System .................................... ACXNOWGEDGME~S ................................................. S o l i d Phase T r a n s i t i o n

...................................................... BIBLIOC-RAmY ....................................................

REFEREXES

105

..........................

7.2

APPENDIX A

93 95 96 98 99 103

106

I m p u r i t i e s in t h e S a l t

SELECTED XYSICAL A N CHEMICAL PROPERTIES OF PROCESS IATERIALS

................................ APPFJDIX B . REFERENCE DRAWINGS ................................. APPENDIX C . MATERIAL SPECIFICATIONS ............................ APPENDIX D . DERIVATION OF EQUATION FOR CALCULATION OF BF3 PARTIAL PRESSURE ................................. APPENDIX E . FREEZE-THAW STRESS TEST ............................

................................

7.1

O f f - G a s System

79 79 83 84 88

108

108 109

110 110

113 121 122

123 125

EXPERIENCE W I T H SODIUM F'LUOROBORATE CIRCULATION I N AN MSRE-SCALE FACILITY A. N . Smith

ABSTRACT A e u t e c t i c mixture of sodium f l u o r o b o r a t e and sodium f l u o r i d e w a s c i r c u l a t e d i s o t h e r m a l l y at a rate of about 800 gpm f o r 11,567 h r i n a 4-in.-IFS Inconel t e s t l o o p as p a r t of t h e program t o e v a l u a t e t h e f l u o r o b o r a t e s a l t f o r use as a secondary c o o l a n t f o r t h e Molten-Salt Breeder Reactor. Except f o r b r i e f p e r i o d s a t 900, 1150, and 1275OF, t h e b u l k s a l t temperature w a s c o n t r o l l e d a t 1025째F. The o b j e c t i v e of t h e experiment w a s t o o b t a i n g e n e r a l experience i n t h e handling and c i r c u l a t i o n of t h e f l u o r o b o r a t e s a l t s , w i t h emphasis on t h e pumping c h a r a c t e r i s t i c s and on t h e d e s i g n and o p e r a t i o n of t h e gas system as it r e l a t e d t o h a n d l i n g BFs and c o n t r o l l i n g t h e s a l t composition. The t e s t r e s u l t s indicat.ed (1)t h a t water t e s t d a t a may be used t o p r e d i c t t h e performance of m o l t e n - s a l t pumps w i t h t h e f l u o r o b o r a t e salt, ( 2 ) t h a t reliable performance may be o b t a i n e d from systems handling BF3 g a s i f p r e c a u t i o n s are t a k e n t o exclude water and waterr e l a t e d i m p u r i t i e s , ( 3 ) t h a t c o n t r o l of t h e s a l t composition should not be a problem, and ( 4 ) t h a t t h e thermal c o n d u c t i v i t y of t h e gas phase above t h e s a l t s u r f a c e may be used as an i n d i c a t o r f o r monitoring t h e s a l t composition. P r e l i m i n a r y t e s t s w e r e made t o examine t h e feas i b i l i t y of p r o t e c t i n g r e a c t o r h e a t - t r a n s f e r s u r f a c e s by p r e f e r e n t i a l d e p o s i t i o n of c o r r o s i o n products i n a c o l d t r a p . F u r t h e r work i s recommended i n t h i s a r e a . The t e s t work i n d i c a t e d t h a t flow r e s t r i c t i o n s i n t h e o f f - g a s l i n e can be e l i m i c a t e d by p r e t r e a t m e n t of t h e salt t o remove v o l a t i l e i m p u r i t i e s and by t h e u s e of a hot-mist t r a p and a c o l d f i l t e r i n t h e o f f - g a s l i n e a t t h e pump bowl o u t l e t . A d d i t i o n a l work i s needed t o improve our understanding of t h e e f f e c t s of cross-mixing between t h e f l u o r o b o r a t e s a l t and t h e r e a c t o r f u e l s a l t and t h e n a t u r e and p r o p e r t i e s of t h e a c i d i m p u r i t i e s i n t h e fluoroborate salt. Key words: r e a c t o r s , secondary c o o l a n t s , sodium f l u o r o b o r a t e , f u s e d salts, boron t r i f l u o r i d e , c o o l a n t l o o p s , Molten-Salt Reactor Experiment, m o l t e n - s a l t pumps.

2 1. INTRODLCTION

A s c u r r e n t l y conceived, m o l t e n - s a l t b r e e d e r r e a c t o r (MSBR) systems

r e q u i r e t h e c i r c u l a t i o n of a secondary coolant s a l t t o t r a n s f e r t h e nuc l e a r h e a t from t h e f u e l s a l t t o t h e steam g e n e r a t o r i n t h e power conv e r s i o n (Rankine c y c l e ) system (see F i g . 1). A mixture of l i t h i u m and b e r y l l i u m f l u o r i d e s w a s used as t h e secondary c o o l a n t i n t h e Molten-Salt Reactor Experiment (MSRE), and t h e performance of t h i s s a l t i n d i c a t e s t h a t it i s s u i t a b l e f o r bISBR u s e .

main disadvantages of i t s use are

h i g h c o s t (about $12/lb) and r e l a t i v e l y h i g h m e l t i n g p o i n t (850°F). Another material, a sodium fluoroborate-sodium f l u o r i d e e u t e c t i c mixture

[ NaBF, -NaF (92-8 mole (about

4% of

$)I,

h a s evoked i n t e r e s t because it c o s t s less

t h e c o s t of t h e Li-Be s a l t ) and because i t s m e l t i n g p o i n t

(725’F) i s low enough t o minimize t h e p r o b a b i l i t y of s a l t f r e e z i n g i n t h e steam g e n e r a t 0 r s . l

A n e x t e n s i v e program h a s been under way a t ORNL t o q u a l i f y t h e f l u o r o b o r a t e s a l t f o r use as t h e secondary c o o l a n t for MSBR s e r v i c e .

a d d i t i o n t o s t u d i e s of b a s i c phjrsical p r o p e r t i e s , e n g i n e e r i n g p r o p e r t i e s , and materials c o m p a t i b i l i t y , t h e program o r i g i n a l l y c a l l e d f o r t e s t i n g t h e f l u o r o b o r a t e s a l t mixture i n t h e FSRE c o o l a n t system under r e a c t o r opera5ing c o n d i t i o n s .

To h e l p us determine d e s i g n and o p e r a t i o n a l changes

t h a t would b e needed at t h e bERE f o r t h e c o o l a n t t e s t , it w a s decided t o make a p r e l i m i n a r y t e s t i n an e x i s t i n g i s o t h e r m a l pump t e s t s t a n d , which

w a s capable of o p e r a t i n g a t t h e flow rate t o 1200°F) of t h e EERE.

and temperature (1000

This r e p o r t d e s c r i k e s t h i s p r e l i m i n a r y t e s t .

Conceptual work s t a r t e d i n June Mach

(850 gpm)

1967; i n i t i a l

loop operation s t a r t e d i n

1968, and t h e t e s t work extended through June 1970. After t h e

p r e l i m i n a r y t e s t w a s under way, a program change r e s u l t e d i n t h e c a n c e l l a t i o n of p l a m t o use t h e f l u o r o b o r a t e s a l t i n t h e MSRE c o o l a n t system. Consequently, t h e work r e p o r t e d h e r e r e p r e s e n t s t h e c u r r e n t t o t a l exper i e n c e w i t h t h e c i r c u l a t i o n of fluoro-Porate s a l t i n an MSRE-scale facility.

ORNL-DWG

68-4192

<Fa

VENT

-COOLING

HOLD UP

PRESSURE

COOLANT SALT PUMP

STEAM GENERATING UNIT NO. 1

DRAIN TANK

TEMP POINT

'-L FREEZE VALVE PROPORTIONAL FLOW VALVE

TO CHEMICAL -PROCESSING

GAS SEPARATOR

-FUEL

__ COOLANT

__--STEAM

**STEAM GENERATING UNIT NO 2 m STEAM GENERATING UNIT NO 3 xu** STEAM GENtRATlNG UNIT NO 4

F i g . 1.

F) @ @

F) 3>

1000 1300 1300 1 1 50 850 1150 1 1 50 1150 850 I 1 50

FLOW

POINT

200 f13/sec

200 50 75 75 75 0-20 16 2 16.2 10

Flow diagram for 2000-MW(e) s t a t i o n .

(3 @)

0 @ @ @

e) @ @)

TEMP 'F

850 850 600 1000 1000 700 950

1250 600 @I 100

FLOW

75 f t % e c 10 2 56 x 106Ib/ hr 2 56x lo6 126x

lo6

126~10~ 4 f t 3/sec 4

420,000 f13/rmn 420,000

TEST OBJECTIVES

When t h e f l u o r o b o r a t e * s a l t i s h e a t e d above i t s m e l t i n g p o i n t , it -.t

+ BF,.

The de-

g r e e of d i s s o c i a t i o n and t h e r e s u l t i n g p a r t i a l p r e s s u r e of BF,

over t h e

d i s s o c i a t e s i n accordance w i t h t h e e q u a t i o n NaBF4

NaF

melt i s a f u n c t i o n of t h e temperature (see Appendix A, S e c t . A.2). 1025째F t h e e q u i l i b r i u m BF,

decomposition p r e s s u r e i s

1 . 4 p s i a ; a t l150째F,

which i s t h e d e s i g n temperature a t t h e c o o l a n t pump i n l e t f o r t h e MSBR, t h e BF3 decomposition p r e s s u r e i s

4.9 p s i a o r o n e - t h i r d of atmosphere.

By way of c o n t r a s t t h e Li-Be c o o l a n t s a l t a t 1025째F has a vapor p r e s s u r e of about

4 x

psia.

I n a system such as t h e MSRE c o o l a n t system,

which o p e r a t e d a t a t o t a l o v e r p r e s s u r e of 20 p s i a , t h e pump bowl gas space and t h e a s s o c i a t e d o f f - g a s stream would Tontain from depending on t h e temperature a t t h e s a l t - g a s i n t e r f a c e .

7 to

25% BF,

This r a t h e r

s i g n i f i c a n t p a r t i a l p r e s s u r e of BF, suggested t h e p o s s i b i l i t y of problems i n t h e c o n t r o l of s a l t composit,ion, i n pump o p e r a t i o n , and i n t h e operat i o n of t h e cover-gas system.

I n a d d i t i o n , so f a r as we know, t h i s w a s

t h e f i r s t a t t e m p t t o c i r c u l a t e molten f l u o r o b o r a t e s a l t i n l a r g e - s c a l e equipment, and it appeared l i k e l y t h a t some unforeseen problem might a r i s e . Therefore, t h e o r i g i n a l o b j e c t i v e s of t h e sodium f l u o r o b o r a t e c i r c u l a t i n g

t e s t l o o p can be summarized as i'ollows: 1. Examine t h e pumping c h a r a c t e r i s t i c s . w i t h similar d a t a f o r t h e Li-Se s a l t .

Compare head-flow d a t a

Determine minimum o v e r p r e s s u r e s

n e c e s s a r y t o suppress c a v i t a t i o n . 2.

Determine what problems might be i n v o l v e d i n monitoring and con-

t r o l l i n g t h e composition of t'ne s a l t .

Accumulate e x p e r i e n c e i n t h e o p e r a t i o n of a f l u o r o b o r a t e c i r c u -

l a t i o n system.

I n p a r t i c u l a r , make o b s e r v a t i o n s on freeze v a l v e opera-

t i o n , s a l t sampling, and t h e handling and c o n t r o l of g a s e s c o n t a i n i n g BF,.

I n g e n e r a l , make n o t e of anything t h a t might be u s e f u l i n t h e de-

s i g n or o p e r a t i o n of a f l u o r o b o r a t e system.

*Unless otherwise i n d i c a t e d , t h e terms f l u o r o b o r a t e or sodium f l u o r o b o r a t e w i l l be used h e r e i n t o d e s i g n a t e t h e NaBF4-NaF (92-8 mole $) e u t e c t i c mixture.

5 W

A f t e r t h e t e s t work w a s under way, two o t h e r items assumed s u f f i c i e n t importance t o warrant d e s i g n a t i o n as a major o b j e c t i v e .

Examine t h e p o s s i b i l i t y of p r e v e n t i n g u n d e s i r a b l e accumulations

of c o r r o s i o n products (such as on h e a t exchanger s u r f a c e s ) by providing f o r p r e f e r e n t i a l deposition i n a cold t r a p .

Determine t h e n a t u r e of m i s t s and vapors discharged from t h e

pump bowl vapor space i n t o t h e o f f - g a s l i n e .

Develop s e p a r a t o r s , t r a p s ,

f i l t e r s , or o t h e r d e v i c e s t h a t w i l l manage t h e s e materials s o as t o minimize flow r e s t r i c t i o n s and f o u l i n g of c o n t r o l v a l v e t r i m i n t h e o f f - g a s system.

SUMJMARY OF TEST RESULTS

3.1 General The t e s t work produced no evidence of any e n g i n e e r i n g problem t h a t would preclude t h e u s e of NaBF,-NaF e u t e c t i c as a secondary c o o l a n t f o r m o l t e n - s a l t r e a c t o r systems.

3.2

Pumping C h a r a c t e r i s t i c s

The r e s u l t s of h y d r a u l i c performance and c a v i t a t i o n t e s t s i n d i c a t e t h a t head-flow and c a v i t a t i o n c h a r a c t e r i s t i c s u s i n g f l u o r o b o r a t e s a l t should be p r e d i c t a b l e from water t e s t data t a k e n w i t h s i m i l a r pumps. C a v i t a t i o n i n c e p t i o n p r e s s u r e s f o r a f l u s h i n g b a t c h of salt were

16% h i g h e r t h a n s i m i l a r data f o r a c l e a n b a t c h of s a l t . This e f f e c t w a s a t t r i b u t e d t o an i n c r e a s e i n BF, p a r t i a l p r e s s u r e r e s u l t i n g from contamin a t i o n of t h e f l u s h i n g s a l t by t h e r e s i d u a l MSRE-type (Li-Be-U-Th) s a l t remaining i n t h e l o o p from p r i o r t e s t work.

3.3

Control of t h e S a l t Composition

E f f o r t s t o e v a l u a t e methods for composition c o n t r o l w e r e hampered by our i n a b i l i t y t o determine t h e composition of t h e s a l t w i t h s u f f i c i e n t accuracy and p r e c i s i o n .

However, a f t e r due c o n s i d e r a t i o n of t h e

6 t e s t data, we b e l i e v e t h a t t h e composition of +,he s a l t remained e s s e n t i a l l y

c o n s t a n t over t h e 11,000-hr p e r i o d of c i r c u l a t i o n , and we f u r t h e r conclude from t h i s t h a t t h e use of a BF, overpressure system w a s s u c c e s s f u l as a composition c o n t r o i method.

O f t e c h n i q u e s c o n s i d e r e d f o r monitoring t h e

s a l t composition, t h e t e s t work i n d i c a t e d t h a t t h e o f f - g a s thermal conduct i v i t y method i s f e a s i b l e and t h a t chemical a n a l y s i s of s a l t samples by use of c w r e n t l y a v a i l a b l e techniques i s u n s a t i s f a c t o r y .

3.4

C c n t r o l l e d Deposition of Corrosion Products

Data w e r e o b t a i n e d on t h e r e l a t i v e s i z e and chemical composition of d e p o s i t s formed on a "cold fir,ger" which w a s i n s e r t e d beneath t h e s u r f a c e of t h e s a l t pool i n t h e pump bowl.

The u l t i m a t e o b j e c t i v e w a s t o d e t e r -

mine i f c o l d t r a p p i n g could be used

ir?_

r e a c t o r secondary c o o l a n t systems

t o c o n t r o l c o r r o s i o n p r o d x t c o z c e n t r a t i o n s and thus t o i n h i b i t t h e f o r mation o f ' h a r x P d deposi5s o ~ C,ke : steam g e n e r a t o r h e a t t r a n s f e r s u r f a c e s . However, t h e t e s t r e s u l t s were t o o meager t o permit any meaningful conc 1 ~i osn s

. 3.5

Analysis acd C o r r e c t i o n of' R e s t r i c t i o n s on t h e Gff-Gas System

Ir_itial o p e r a t i o n s w e r e c h a r a c t e r i z e d by flow r e s t r i c t i o n s i n t h e

%-e t r o - i d e w a s t r a c e d t o a mixture of materiais ( s a l t

off-gas l i c e . x i s t s , ac:ds,

metal r o r r o s i c n p r o d u c t s ) c a r r i e d from t h e pump bowl by

a purge-gas stream and d e p o s i t e d i n u c d e s i r a b l e p l a c e s by condensation and/or g r a v i t y .

Test r e s f i t s Cndicate t h e problem can b e c o n t r o l l e d by

a p r o p e r l y designed system of t r a p s acd f i l t e r s i n t h e o f f - g a s l i n e a t t h e pm1p bowl outle',

Also t h e problem may b e a m e l i o r a t e d by p r e t r e a t -

ment of t h e s a l t t o minimize i n p u r i t i s s and by d e s i g n i n g t h e pump s o as t o minimize formation of s a l t m i s t i n t h e p m p bowl gas space.

3.6 Miscellaneous Observations Handling and c i r c u l a . t i o n of t h e f l u o r o k o r a t e salt, were accomplished without d i f f i c u l t y u s i n g r o u t i n e m o l t e n - s a l t h a n d l i n g t e c h n i q u e s .

7 W

i n c i d e n t i n v o l v i n g leakage of s a l t t o t h e atmosphere dramatized t h e e s s e n t i a l l a c k of secondary e f f e c t s . l e a k - t i g h t system f o r handling BF,

The importance of providing a c l e a n ,

was confirmed.

The performance of t h e

s a l t freeze v a l v e and of v a r i o u s i n s t r u m e n t s f o r measuring p r e s s u r e and flow i n b o t h t h e s a l t and g a s systems appeared t o be r e l i a b l e and adequate.

DESCRIPTION OF TEST FACILITY

4 . 1 General The t e s t work w a s done i n an e x i s t i n g f a c i l i t y t h a t w a s modified t o

meet t h e requirements of t h e f l u o r o b o r a t e t e s t . structed i n

The f a c i l i t y w a s con-

1956 and w a s o p e r a t e d f o r many thousands of hours c i r c u l a t i n g

NaK i n o r d e r t o o b t a i n performance d a t a on model PKP pumps f o r t h e A i r c r a f t Reactor T e s t (ART).

I n 1962 t h e f a c i l i t y w a s r e a s s i g n e d t o t h e

Molten-Salt Reactor Program and between 1962 and 1966 w a s o p e r a t e d f o r more t h a n 17,000 h r i n t h e c i r c u l a t i o n of m o l t e n - f l u o r i d e s a l t s of t h e t y p e (Li-Be-U-Th)

used i n t h e MSRE.

Changes made p r i o r t o t h e s t a r t of

t h e f l u o r o b o r a t e t e s t i n c l u d e d p r o v i s i o n s t o o b t a i n s a l t samples, r e v i s i o n s t o t h e purge- and o f f - g a s systems t o provide proper equipment f o r handling BF,

gas, r e v i s i o n t o t h e d r a i n l i n e f r e e z e v a l v e t o b e t t e r

simulate t h e MSRE i n s t a l l a t i o n , and r e v i s i o n s t o t h e containment and v e n t i l a t i o n systems t o i n s u r e proper containment and d i s p o s a l of any vapors t h a t might a c c i d e n t a l l y l e a k from t h e l o o p .

lems that

As a r e s u l t of prob-

a r o s e d u r i n g t h e course of t h e f l u o r o b o r a t e t e s t work, t h e

BF3 feed system w a s modified, and miscellaneous r e v i s i o n s were made i n t h e purge- and o f f - g a s systems p r i m a r i l y t o cope w i t h flow r e s t r i c t i o n problems.

For d e s i g n d e t a i l s of t h e complete f a c i l i t y see t h e drawings

l i s t e d i n Appendix B.

4.2

S a l t P i p i n g and Components

The s a l t p i p i n g i s shown i n s i m p l i f i e d o u t l i n e i n F i g . 2 . and p i p i n g w e r e f a b r i c a t e d from I n c o n e l . except f o r about W

4ft

The p i p e s i z e w a s

The pump

4 in.

of 3 1 / 2 - i n . IPS a t t h e pump d i s c h a r g e .

IPS

The pump

ORNL OWG 7 2 - 2 0 7 3

, 200 hp MOTOR

PKP PUMP.

-4-in. I P S

VENTUR METER, SALT FLOW THROTTLE VALJE -VEPIITURI T4RCIAT PMD'C49. VENTJRI IYLE' PUC!!J4A -

DQAIN LINE

@ R A I N TANK 8 $t3

?ig. 2. Sirnplifieci schematic o f f l u o r o b o r a t e c i r c u l a t i o n loop.

9 w a s l o c a t e d a t t h e p o i n t of m a x i m u m e l e v a t i o n .

From t h e pump d i s c h a r g e

t h e s a l t flowed i n o r d e r through an upper h o r i z o n t a l s e c t i o n , a v e r t i c a l l y o r i e n t e d 180" r e t u r n bend, a lower h o r i z o n t a l s e c t i o n , a v e n t u r i

From t h e v a l v e , which w a s a t t h e p o i n t

element, and a t h r o t t l e v a l v e .

of minimum e l e v a t i o n , t h e flow proceeded d i r e c t l y upward about 3 f t t o t h e pump s u c t i o n .

Each h o r i z o n t a l s e c t i o n w a s about

p i t c h e d s l i g h t l y t o f a c i l i t a t e d r a i n i n g of t h e l o o p .

f t long and w a s

An 8 - f t 3 I n c o n e l

d r a i n t a n k s e r v e d as s t o r a g e space f o r t h e s a l t i n v e n t o r y when t h e fac i l i t y w a s not i n operation.

A 3/4-in.-IPS

d r a i n l i n e connected t h e

d i p l e g i n t h e d r a i n t a n k t o t h e bottom of t h e t h r o t t l e v a l v e housing i n t h e loop.

T r a n s f e r of s a l t w a s accomplished by means of gas p r e s s u r e ,

and a freeze v a l v e (see S e c t i o n t a n k from t h e l o o p .

6 . 4 ) w a s provided t o i s o l a t e t h e d r a i n

Table 1 l i s t s p r i n c i p a l d a t a r e l a t i n g t o l o o p geome-

try. The pump, d e s i g n a t e d as model PKP, i s a f o r e r u n n e r of t h e pumps used i n t h e MSRE f u e l and c o o l a n t systems.

It i s a c e n t r i f u g a l sump pump with

i n t e g r a l pump t a n k and v e r t i c a l s h a f t ( F i g . t e s t work t h e pump speed w a s 1800 rpm.

3 ) . During t h e f l u o r o b o r a t e

The upper e x t e r i o r s u r f a c e of t h e

i m p e l l e r i s equipped w i t h r i b s which f u n c t i o n t o c o n t r o l t h e rate of leakage ( f o u n t a i n f l o w ) from t h e v o l u t e i n t o t h e pump t a n k by way of t h e upper s h a f t seal.2

Baffles and a t h e r m a l s h i e l d s e r v e t o p r o t e c t t h e b e a r i n g

c a v i t y from excess t e m p e r a t u r e .

A f o r c e d - c i r c u l a t i o n o i l system l u b r i c a t e s

t h e b e a r i n g s and cools t h e thermal s h i e l d . The shaft o i l seal i s a m e t a l - g r a p h i t e r o t a t i n g mechanical seal.

t h a t l e a k s p a s t t h e seal d r a i n s i n t o a c a t c h b a s i n ( F i g .

4).

Of1

A top hat or

dam i s provided t o minimize t h e tendency f o r leakage o i l t o flow down t h e

pump s h a f t t o t h e pump bowl.

A continuous flow of i n e r t gas (helium or

argon) serves as a s h a f t purge. i n t o two streams.

A t t h e s h a f t annulus t h e flow i s s p l i t

One stream, equal t o about

90% of t h e t o t a l , flows down

t h e s h a f t i n t o t h e pump bowl vapor space, s e r v i n g t o i n h i b i t back d i f f u s i o n of pump bowl vapors.

The remaining p o r t i o n of t h e purge gas flows up t h e

s h a f t over t h e r o t a t i n g seal and through t h e o i l c a t c h b a s i n .

The p i p i n g

i s arranged s o t h a t most of t h e accumulated o i l i s f o r c e d o u t of t h e c a t c h

b a s i n w i t h t h e gas stream and i n t o an o i l c a t c h tank f u r t h e r downstream.

ORNL-LR-DWG

243578

LOW T E M P E R A T U R E ROTARY A S S E M B L Y

INCHES

MECHANICAL SHAFT SEAL CATCH B A S I N

---

THERMAL BARRIER-.

P U M P TANK

MAXIMUM PERMISSIBLE LEVELU P P E R I M P E L L E R CASING N O R M A L OPERATING L E V E L

MINIMUM PUMPING LEVEL

INLET

Fig. 3.

FK? ?-map c r o s s s e c t i o n .

ORNL DWG 72-2075

FLOW CONTROL

Fig.

â&#x20AC;&#x2122;

4. Schematic

diagram of shaft purge system on PKP pump.

12 The gas p r e s s u r e i n t h e b e a r i n g c a v i t y i s c o n t r o l l e d a t 1.150 2 p s i above

t h e pump bowl p r e s s u r e s o t h a t o i l seal leakage flows i n t o t h e c a t c h basin.

Table 1. D e s c r i p t i v e d a t a on f l u o r o b o r a t e c i r c u l a t i o n l o o p

Total

Circulating loop

Pump tank

S a l t volume, f t 3

4.1

0.5

4.6

S a l t mass, l b

476

534

Gas volume," ft3

1.2

S u r f a c e area of wetted metal, f t 2 .

Free s u r f a c e of s a l t , f t 2

4 3

Length of p i p i n g , f t

54 3 40

Linear v e l o c i t y of s a l t a t 800 gpm, f p s

7.7 x io5

T y p i c a l Reynolds number a t 1025 "F ~~~~

a Assuming s a l t l e v e l a t 2 i n . above v o l u t e midplane.

4.3

S a l t Sampling Device

S a l t samples were o b t a i n e d by dipping a copper bucket i n t o t h e s a l t ir,

t h e pump bowl.

Although t h e pump bowl i n v e n t o r y w a s n o t i n t h e main

c i r c u l a t i n g stream, t h e leakage through t h e pump s h a f t l a b y r i n t h (fount a i n flow) w a s e s t i m a t e d t o be enough t o cause a complete i n t e r c h a n g e with t h e c i r c u l a t i n g i n v e n t o r y e v e r y 2 min, and s o t h e s a l t samples were assumed t o be r e p r e s e n t a t i v e of t h e material i n t h e c i r c u l a t i n g stream. The sample t u b e s were hydrogen f i r e d b e f o r e use t o remove oxide s c a l e , and a s p e c i a l p i p e housing w a s provided t o prevent c o n t a c t w i t h a i r bef o r e and d u r i n g t h e sampling p r o c e s s . foll.ows:

The sample device ( F i g .

The sampling procedure w a s as

5 ) was screwed o n t o t h e p i p e n i p p l e

on t h e pump bowl sample a c c e s s p i p e .

The sample u n i t b a l l v a l v e w a s

opened, and t h e sample u n i t and n i p p l e were purged and evacuated t o remove w e t a i r and t h e n were p r e s s u r i z e d t o about 2 p s i above t h e pump I

. ORNL DWG 72-?076

7 --

SAMPLE STICK,

_---V4-in - O D Cu TUBE

ENDS OF TUBES SEALED OFF

I 3/8-1n-OD Cu TUBE

g3? X 1/2-m

SLOT

4'n.

2'/2 in

SAMPLE VOLUME 3 cm3 SAMPLE WEIGHT 5 G g

.-.-

?EFLON SLIDING SEAL

PURGE %

Yf Fig. 5 .

PROTECTIVE HOUSING

PUMP TANK BALL VALVE

Salt sampling d e v i c e .

14 bowl p r e s s u r e .

The pump bowl b a l l v a l v e was t h e n opened and t h e sample

t u b e i n s e r t e d u n t i l t h e bucket bottomed i n t h e pump t a n k . s e r t i o n p e r i o d of 10 t o

A f t e r an i n -

1 5 s e c , t h e sample bucket w a s withdrawn i n t o t h e

p r o t e c t i v e housing, and t h e pump t a n k b a l l v a l v e w a s c l o s e d . cooldown p e r i o d of a t least

After a

1.5 min, t h e sample bucket w a s removed from

i t s p r o t e c t i v e p i p e housing, c u t l o o s e from t h e 1 / 4 - i n . copper t u b e ext e n s i o n r o d , and p l a c e d i n a sample j a r t h a t had been f l u s h e d w i t h argon t o remove excess w e t a i r .

4 . 4 Heating and C o n t r o l l e d V e n t i l a t i o n

The l o o p w a s h e a t e d w i t h Calrod h e a t e r s a p p l i e d t o b a r e p i p e and ceramic h e a t e r s i n s t a l l e d on t h e pump t a n k , d r a i n t a n k , and a i r c o o l i n g The h e a t e r i n p u t w a s c o n t r o l l e d by manually a d j u s t e d V a r i a c s .

shrouds.

The c i r c u l a t i n g s a l t was cooled by u s i n g t h e s u c t i o n of t h e v e n t i l a t i o n blower t o d r a w a c o n t r o l l e d flow of a i r through a n n u l i formed on p o r t i o n s of each h o r i z o n t a l s e c t i o n of t h e p i p i n g ( F i g . 6 ) .

Except for t h e t o p

p o r t i o n o f t h e pump, t h e l o o p proper w a s completely e n c l o s e d i n s h e e t

metal.

The blower w a s used t o maintain a s l i g h t n e g a t i v e p r e s s u r e i n

t h e e n c l o s u r e , s o t h a t any gas leakage from t h e l o o p would be d i l u t e d w i t h a i r and d i s c h a r g e d from t h e s t a c k on t h e r o o f .

The l o o p o p e r a t i n g

temperature w a s maintained by b a l a n c i n g t h e power s u p p l i e d by t h e pump and by t h e r e s i s t a n c e h e a t e r s a g a i n s t t h e power removed by loss t o t h e s u r r o w d i n g s and by t h e c o o l i n g a i r .

4.5

Gas System Design

Gas i n p u t w a s c o n s t a n t and w a s made up of t h r e e s e p a r a t e streams

(Fig.

7):

(1) t h e s h a f t purge, normally about 950 c$/min

of helium,

whose f u n c t i o n w a s t o i n h i b i t d i f f u s i o n of pump bowl vapors i n t o t h e b e a r i n g c a v i t y ; ( 2 ) t h e instrument l i n e purge, about 230 c$/min

helium, which maintained a continuous sweep of purge g a s through t h e l i n e t h a t w a s used t o s e n s e pump bowl p r e s s u r e and a l s o s e r v e d as t h e vapor phase t a p f o r t h e s a l t l e v e l i n d i c a t o r ; and ( 3 ) t h e mixed-gas

ORFUL-DWG 7 2 - 2 0 7 7

Fig.

Loop v e n t i l a t i o n and t e m p e r a t u r e c o n t r o l .

ORNL-DWG 72-2078

@--------? I

TO STACK

SHAFT PURGE, 950cm3/min

LOWER SHAFT SEAL PURGE FLOW, t00cm3/min,

O T, --

PUMP BOWL PRESSURECONTROLVALVE PUMP BOWL

FROM PUMP BOWL PRESSURE TRANSMITTERPUMP BOWL SALT LEVEL

@ CONSTANT A P FLOW CONTROLLER

BF3. 50cm5/min (BASED ON 1025.F SALT TEMPERATURE)

Fig. 7. loop.

Simplified diagram of gas system, NaBF4 circulation t e s t , PIP

f e e d , about 370 cn?/min of helium p l u s BF,

, which

provided t h e n e c e s s a r y

BF, f e e d t o t h e pump bowl and a l s o s e r v e d as t h e h i g h s i d e t a p f o r t h e s a l t l e v e l i n d i c a t o r . The BF, flow r e q u i r e d f o r 1025째F o p e r a t i o n w a s 50

When t h e l o o p w a s o p e r a t e d a t o t h e r s a l t t e m p e r a t u r e s , t h e BF,

cn? /min.

flow w a s v a r i e d a c c o r d i n g l y , and t h e helium was a d j u s t e d t o keep t h e t o t a l mixed-gas flow a t

370

crr?/min.

There were two e f f l u e n t gas streams from t h e system.

s m a l l f r a c t i o n of t h e s h a f t purge, about 100 c$/min,

One w a s a

which flowed up

t h e s h a f t and s e r v e d t o keep o i l leakage swept out of t h e pump.

flow was controlled a t a constant value.

This

The o t h e r e f f l u e n t , t h e main

off-gas stream, c o n s i s t e d o f t h e remainder of t h e s h a f t purge and t h e o t h e r gas flows t h a t e n t e r e d t h e pump bowl vapor s p a c e .

The flow rate

i n t h e main o f f - g a s stream w a s dependent on t h e pump bowl p r e s s u r e cont r o l . v a l v e , which o p e r a t e d t o keep t h e pump bowl g a s o v e r p r e s s u r e a t t h e desired set p o i n t .

Since t h e o t h e r gas flows were c o n s t a n t , when t h e

system w a s a t s t e a d y s t a t e t h e o f f - g a s flow w a s c o n s t a n t and e q u a l t o t h e t o t a l i n p u t minus t h e lower seal purge f l o w . B a l l v a l v e s with packed s t e m seals were used i n t h e s a l t sample a c c e s s l i n e t o permit passage of t h e sample t u b e s and t h e c o l d - f i n g e r assembly.

The experimental t r a p s and f i l t e r s i n t h e o f f - g a s l i n e a l s o

were equipped w i t h b a l l - t y p e i s o l a t i o n v a l v e s because t h e s t r a i g h t through flow p a t h minimized t h e tendency for s a l t p a r t i c l e s and o t h e r contaminants t o c o l l e c t i n t h e v a l v e s .

Otherwise, t h e gas system w a s

equipped with globe-type v a l v e s t h a t had packed s t e m seals i n e x i s t i n g

areas and with some f e w e x c e p t i o n s demountable bellows stem seals i n newly i n s t a l l e d areas.

Check v a l v e s and r e l i e f v a l v e s were of t h e

s p r i n g - l o a d e d poppet t y p e .

Body m a t e r i a l w a s brass and t r i m w a s brass

or Teflon, a l t h o u g h i n some c a s e s s t a i n l e s s s t e e l v a l v e s were s u b s t i t u t e d because of a v a i l a b i l i t y .

End connections were 1/4-in.-OD t u b i n g or

1/4 i n .

IPS, except where l a r g e r s i z e s were d i c t a t e d by s p e c i f i c o p e r a t i n g r e q u i r e ments. models.

A l l v a l v e s w e r e s e l e c t e d from e x i s t i n g , commercially a v a i l a b l e

4.6, BF,

Disposal

The loop w a s o p e r a t e d f o r t h e most p a r t w i t h t h e s a l t temperature

at 1025째F and t h e t o t a l overpressure a t 38.7 p s i a .

A t lO25"F, t h e BF,

p a r t i a l p r e s s u r e i s 1.35 p s i , and so t h e BF, c o n c e n t r a t i o n i n t h e o f f gas stream was about

3.5% by volume.

A f t e r p a s s i n g through t h e l o o p

p r e s s u r e c o n t r o l valve, t h e o f f - g a s stream w a s passed through a mineralo i l bubbler t o i n h i b i t back d i f f u s i o n of m o i s t u r e .

The gas stream w a s

t h e n vented i n t o t h e 1 2 - i n . s u c t i o n l i n e t o t h e s t a c k blower.

The o f f -

1 . 5 l i t e r s / n i n , and t h e blower flow w a s 2500 cfm; s o t h e c o n c e n t r a t i o n of BF, i n t h e s t a c k w a s (1.5/28.3)(0.035/2500), or 0.7 gas flow rate w a s

ppm.

D i l u t i o n Icy t h e atmosphere probably reduced t h e c o n c e n t r a t i o n by a

f a c t o r of 100, s o t h i s method of d i s p o s i n g of t h e BF,

k e p t t h e atmospheric

c o n c e n t r a t i o n w e l l below t h e continuous exposure l i m i t of 1 ppm.

4.7

Instrument and Controls

Approximately 32 sheathed Chronel-Alumel thermocouples were provided on t h e s a l t system t o monitor t h e s a l t t e m p e r a t u r e .

One thermocouple w e l l

w a s immersed i n t h e s a l t i n t h e pump bowl and a n o t h e r w a s i n s t a l l e d i n t h e d r a b tank; a l l o t h e r thermocouples were s t r a p p e d t o s u r f a c e s of p i p i n g

and components.

S a l t p r e s s u r e w a s measured by p r e s s u r e t r a n s m i t t e r s (FT),

which use a f l e x i b l e t h i n - m e t a l diaphragm and an NaK-filled t r a n s m i s s i o n l i n e t o r e l a y p r e s s u r e impulses t o a remote r e c e i v e r .

S a l t flow w a s i n d i -

c a t e d by t h e OP a c r o s s a f u l l - f l o w .Jenturi, and t h e AP was measured by t h e d i f f e r e n c e i n r e a d i n g between a FT a t t h e v e n t u r i i n l e t and a n o t h e r a t t h e venturi t h r o a t .

S a l t flow could b e v a r i e d ketween 400 and 1000 gpm by ad-

justing t h e t h r o t t l e valve.

A metal kellows w a s used f o r t h e s t e m seal on

t h e s a l t v a l v e , and an actomatic g a s - p r e s s u r i z i n g system w a s connected t o a chamber surrounding t h e bellows t o i n s u r e t h a t t h e d i f f e r e n c e i n p r e s -

sure a c r o s s t h e bellows w a s always c o n t r o l l e d w i t h i n a c c e p t a b l e l i m i t s . Spark plug probes were provided i n t h e pump bowl and d r a i n t a n k f o r s i n g l e p o i n t i n d i c a t i o n of s a l t l e v e l .

A gas bubbler t u b e , mentioned e a r l i e r ,

w a s provided i n t h e pump bowl f o r continuous s a l t l e v e l i n d i c a t i o n over a range of

10.75 i n .

A high-frequency conductance probe w a s used v e r y

b r i e f l y f o r s a l t l e v e l i n d i c a t i o n (see S e c t . 6 . 6 ) .

P r e s s u r e gages w i t h s i l v e r - s o l d e r e d phosphor-bronze Bourdon t u b e s

were used f o r gas l i n e s c o n t a i n i n g BF,. BF,

The p r e s s u r e t r a n s m i t t e r s f o r

flow and s a l t l e v e l had w e t t e d p a r t s of s t a i n l e s s s t e e l o r T e f l o n .

The 0- t o 50-psig pump bowl p r e s s u r e t r a n s m i t t e r had a h e l i c a l element. C a p i l l a r i e s were used f o r gas flow elements.

The c a p i l l a r y f o r t h e BF,

flow element (FE-B9) w a s 0.031.i n . i n i n s i d e diameter by 45 i n . long, and t h e c a l i b r a t e d BF, s c a l e (16 i n . %O)

flow rate a t 40 p s i g metering p r e s s u r e and

w a s 330 c$/min.

The BF,

8076

c a l i b r a t i o n s were done

using a w e t t e s t meter f i l l e d w i t h mineral o i l .

Constant AP flow con-

t r o l l e r s were used f o r c o n t r o l of gas flow, w i t h t h e i n p u t flows r e f e r enced t o t h e 40-psig supply p r e s s u r e and t h e lower seal purge r e f e r e n c e d t o atmosphere.

Off-gas letdown w a s c o n t r o l l e d by a pneumatic c o n t r o l

v a l v e w i t h s t a i n l e s s s t e e l body and t r i m , gasketed bellows stem s e a l , and a Cv of 0.01. The t h e r m a l c o n d u c t i v i t y c e l l w a s c o n s t r u c t e d of tungsten-rhenium elements, brass element block, and s i l v e r - s o l d e r e d s t a i n l e s s s t e e l t u b i n g leads.

The c e l l temperature w a s c o n t r o l l e d a t 100째C, and sample and r e f -

erence gas flows were 100 c$/min.

The o f f - g a s sample t a k e - o f f p o i n t w a s

j u s t upstream of t h e p r e s s u r e c o n t r o l v a l v e , s o t h e r e w a s a t i m e l a g of 1 t o 2 min between changes a t t h e pump bowl o u t l e t and c e l l r e s p o n s e .

Figures 8 t o 10 show t h e main c o n t r o l p a n e l , t h e EF,

supply c u b i c l e ,

and t h e o f f - g a s c u b i c l e .

TEST PROCEDURES, OBSERVATIONS, AND CONCLUSIONS FOR THE PRINCIPAL TESTS

5.1

Pumping C h a r a c t e r i s t i c s

The t e s t w a s designed t o o b t a i n head-flow and c a v i t a t i o n i n c e p t i o n d a t a and, by comparing t h e s e d a t a w i t h w a t e r and l i q u i d - m e t a l data f o r t h e same pump, t o l e n d assurance t o the assumption t h a t w a t e r t e s t data may be used to p r e d i c t t h e performance of similar pumps when handling f l u o r o b o r a t e salts.3

A b r i e f d i s c u s s i o n of t h e t e s t s i s g i v e n below;

f o r f u r t h e r information see Refs.

3 and 4.

Fig.

8. Main control panel, fluoroborate c i r c u l a t i o n (PKP) t e s t .

Fig.

BF3 supply cubicle.

The t e s t s were made a t a pump speed of 1800 rpm and a t v a r i o u s s a l t temperatures i n t h e range 900 t o 1300째F.

For t h e head-flow t e s t s t h e

procedure w a s t o a d j u s t t h e s a l t temperature t o t h e d e s i r e d p o i n t and t h e n t o vary t h e s a l t flow by a d j u s t i n g t h e p o s i t i o n of t h e loop t h r o t t l e The procedure f o r t h e c a v i t a t i o n i n c e p t i o n t e s t s w a s t o a d j u s t

valve.

t h e s a l t temperature t o t h e d e s i r e d p o i n t and, with flow c o n s t a n t a t

750

gpm, t o reduce t h e gas overpressure i n f i x e d decrements u n t i l t h e drop i n discharge head p e r u n i t decrease i n p r e s s u r e showed a d i s p r o p o r t i o n a t e change. The h y d r a u l i c performance data are compared w i t h H 2 0 and NaK data i n F i g . 11. The e x c e l l e n t agreement between r e s u l t s from a l l sources c r e a t e s confidence t h a t t h e head-flow c h a r a c t e r i s t i c s of t h e PKP pump could w e l l have been adequately p r e d i c t e d , based on t h e r e s u l t s of a v a i l a b l e H,O and NaK t e s t s .

As a c o r o l l a r y , we can conclude t h a t t h e performance of s i m i -

l a r pwnps, such as t h e MSFB c o o l a n t s a l t pump, could be adequately p r e d i c t e d based on water t e s t r e s u l t s . C a v i t a t i o n d a t a f o r t h e c l e a n charge* of s a l t i n d i c a t e d t h a t t h e i n c e p t i o n of c a v i t a t i o n f o r f l u o r o b o r a t e s a l t can be c o r r e l a t e d on t h e basis of NPSH ( n e t p o s i t i v e s u c t i o n head) and vapor p r e s s u r e (see F i g . 12).

Data f o r t h e f l u s h charge of salt showed c a v i t a t i o n p r e s s u r e s from

7 t o 16% h i g h e r t h a n t h o s e f o r t h e c l e a n charge.

This e f f e c t i s a t t r i -

b u t e d t o t h e f a c t t h a t t h e f l u s h i n g charge contained t h e r e s i d u e of a molten s a l t ( d e s i g n a t e d BULT-4) t h a t had been used i n t h e previous t e s t work i n t h e f a c i l i t y . c i l i t y was that a

16%

The t o t a l charge of f l u s h s a l t i n t o t h e t e s t fa-

689 l b , and t h e e s t i m a t e d r e s i d u e of f u e l s a l t w a s 26 l b ; so r i s e i n p a r t i a l p r e s s u r e a t 1150째F r e s u l t e d from adding about

by weight of f u e l t o t h e c o o l a n t .

Tables 2 and 3 p r e s e n t data on t h e

compositions of t h e s a l t charges.

%e term " c l e a n charge" i s used t o d e s i g n a t e t h e mixture of s a l t t h a t r e s u l t e d when t h e new b a t c h of NaBF4 w a s added t o t h e h e e l ( e s t i mated t o b e about 1-7l b ) of f l u s h s a l t which remained i n t h e system after d r a i n i n g out t h e f l u s h i n g charge.

i20

I 0 FLUOROBORATE AT 9 0 0 째 F

FLUOROBORATE AT1150"F --t

+ .

-NJK (1200째F)

SPEED i795 rpm

400

800

600

4000

FLOW (9Pm)

Fig. 11. Comparison of PKP pump characteristics with sodium f l u o r o borate, MaK, and water.

0 RN L- OWG- 72- 2079

35 SALT FLOW: 750 gpm PUMP SPEED: 4800 rpm

NPSH AT CAVITATION INCEPTION

---. CAVITATION INCEPTION CLEAN CHARGE

._ 0 20

..0.. v)

3 v)

P a

45 it

SEE APPENDIX D

I - t - CALCULATED

0 900

1000

4100

1200

4300

SALT TEMPERATURE (OF)

Fig. 12. C a v i t a t i o n d a t a f o r PKP pump w i t h NaBF4-NaF e u t e c t i c s a l t . ( a ) Pump NPSH requirements ( R e f . 3 ) ; (b) vapor p r e s s u r e of sodium f l u o r o borate (eutectic) ( R e f . 5 ) .

26 Composition of salts c i r c u l a t e d i n F'KP-1 l o o p

Table 2 .

Composition ( w t

BULT-4 s a l t

formerly i n loop"

F l u o r o b o r a t e s a l t f l u s h charge' Fluoroborate s a l t c l e a n chargeb

9.7

5.8 5.1 20.0 59.3 0.20 0.18 0.26 0.24 21.2 9 . 3 66.9 0.05 0.02 0.02 0.10 20.9 9.3 68.0

a F i g u r e s for BULT-4 salt are c a l c u l a t e d (LiF-BeF, -ThF4 -UF4 = 65-30-4-1mole %). bFigures for f l u o r o b o r a t e salts are averages of a l l samples analyzed d u r i n g t h e e n t i r e t e s t program.

Table 3.

R e l a t i v e amounts of f u e l s a l t c o n s t i t u e n t s i n f l u o r o b o r a t e charges

S a l t mixture

Method of determination

Moles p e r 1000 moles N a

Flush charge

Calculated"

0.9

3 00

Flush charge

Chemical a n a l y s i s

1.0

1.o

Clean charge

Chemical a n a l y s i s

32 8

0.08

0.4

a Based on G89 lb f l u s h sa1.t and an e s t i m a t e d h e e l o f 26 lb.

5.2

BULT-4

Control of t h e S a l t Composition

It i s d e s i r a b l e t o keep t h e s a l t a t or n e a r t h e e u t e c t i c (NaBF4-NaF 92-8 mole %) composition i n o r d e r t o t a k e advantage of t h e minimum m e l t i n g point* (Appendix A, F i g . A.l).

The h i g h BF,

p a r t i a l pressure, t o -

g e t h e r w i t h t h e continuous flow o f purge gas through t h e pump bowl vapor *Melting p o i n t as used h e r e i n r e f e r s t o t h e a p p r o p r i a t e p o i n t on t h e liquidus curve.

space, provides a mechanism f o r l o s s of BF,

and a change i n t h e composition

The o b j e c t i v e of t h i s phase of t h e t e s t l o o p work w a s t o de-

of t h e s a l t .

termine t h e problems t h a t might be a s s o c i a t e d w i t h composition c o n t r o l .

p r e l i m i n a r y survey r e v e a l e d t h e following key p o i n t s .

1. Loss of BF3 would s h i f t t h e composition i n t h e d i r e c t i o n of lower NaBF4 c o n t e n t .

The r e s u l t a n t i n c r e a s e i n m e l t i n g p o i n t would i n c r e a s e t h e

p r o b a b i l i t y of p r e c i p i t a t i n g NaF i n t h e c o o l e r areas of t h e system, such as i n t h e steam g e n e r a t o r t u b e s .

The suggested s o l u t i o n w a s t o f e e d BF3

gas i n t o t h e pump bowl gas space a t a rate such t h a t t h e p a r t i a l p r e s s u r 5 of BFa, based on BF3 flow and t o t a l gas flow, i s e q u a l t o t h e e q u i l i b r i u m BFs p r e s s u r e of t h e s a l t , based on t h e d e s i r e d s a l t composition and on t h e temperature of t h e s a l t a t t h e s a l t - g a s i n t e r f a c e . 2.

If a BF3 f e e d system i s used and t h e feed rate i s t o o high, t h e

composition would be s h i f t e d i n t h e d i r e c t i o n of i n c r e a s e d NaBF4 c o n t e n t . On t h i s s i d e of t h e e u t e c t i c , t h e r i s e i n m e l t i n g p o i n t i s l i m i t e d t o a moderate 27"F, b u t t h e i n c r e a s e i n BF3 p a r t i a l p r e s s u r e might be i n t o l e r s For example, a t l150째F t h e BF3 p a r t i a l p r e s s u r e would i n c r e a s e from

ble.

5 t o 30 p s i a 3.

i f t h e NaBF4 f r a c t i o n i n c r e a s e d from 92 t o

98.5 mole '$.

Rates of change i n t h e s a l t composition are l i k e l y t o be rela-

t i v e l y low, because t h e amount of BF,

i n t h e s a l t i s very l a r g e compared

w i t h t h e rate a t which t h e BF3 would normally be added or removed by the gas stream.

i s removed a t t h e m a x i m u m rate, t h a t i s , no

Thus, i f BF,

attempt i s made t o add BF3 t o t h e system (and i g n o r i n g t h e decrease f n p a r t i a l p r e s s u r e w i t h composition), t h e t i m e ( i n days) r e q u i r e d t o produce a change of 1% i n mole f r a c t i o n would b e 2 . 4 x

(Wo/F)(Pt /P b ) ,

where Wo i s o r i g i n a l weight of s a l t ( l b ) assuming a 92-8 mole i s t o t a l gas flow (cfm), P

t o t a l gas p r e s s u r e ( p s i a )

'$ mix, F

i s p a r t i a l p r e s s u r e of B F ~ ( p s i a ) , and pt i s Assuming a BF3 p a r t i a l p r e s s u r e of

psia

( s a l t temperature = 1150째F) and a t o t a l p r e s s u r e of 25 p s i a , t h e above e x p r e s s i o n was a p p l i e d t o t h r e e d i f f e r e n t systems w i t h t h e r e s u l t s g i v e n below.

Inventory Ob)

System

MSRE coolant system

700 5,000

MSBR c o o l a n t system

5OO,OOO

NaBF, t e s t f a c i l i t y

Flow (Cf-4

Time r e q u i r e d f o r 1 mole % change (days 1

1.7

0.05 0.05 2

We n o t e t h a t even f o r a r e l a t i v e l y small system such as t h e t e s t f a c i l i t y , almost two days would be r e q u i r e d t o produce t h e i n d i c a t e d change.

In the

MSBR system, even i f t h e e s t i m a t e d i n v e n t o r y i s h i g h by a f a c t o r of 10, t h e e l a p s e d t i m e would s t i l l b e t h r e e days.

W e a l s o n o t e t h a t t h e times

r e q u i r e d t o reduce t h e NaBF4 mole f r a c t i o n would a c t u a l l y be l o n g e r t h a n i n d i c a t e d s i n c e t h e BF, of BF,,

p a r t i a l p r e s s u r e , and hence t h e rate of removal

would d e c r e a s e as t h e NaBF,

f r a c t i o n decreased.

If w e look at

t h e c a s e where t h e s a l t composition i s being s h i f t e d upward because of t h e a d d i t i o n of an excess of BF,,

w e note t h a t t h e rate of change of s a l t

composition i s p r o p o r t i o n a l t o t h e d i f f e r e n c e between t h e BF,

partial

p r e s s u r e of t h e salt and t h e EF3 p a r t i a l p r e s s u r e based on t h e gas flows. I n o r d e r t o have a r a t e of i n c r e a s e of NaEF4 f r a c t i o n numerically e q u a l t o t h e m a x i m u m rat.e of d e c r e a s e p o s t u l a t e d i n t h e example above, it would ‘ce necessary t o assume a 10%

e r r o r i n t h e c o n t r o l of t h e BF,

some a p p r o p r i a t e com‘cination of e r r o r s i n t h e BF,

gas flow or

and helium f l o w s .

W e

c o n s i d e r e r r o r s of t h i s magnitude t o be v e r y u n l i k e l y i n a p r o p e r l y i n s t r 7 m e n t e d system and hence conclude t h a t rates of change of NaBF, f r a c t i o n i c t h e upward d i r e c t i o n w i l l b e no g r e a t e r t h a n , and are l i k e l y t o be somewhat l e s s C,han, t h e m a x i m u m rates of change of NaBF,

fraction

t h a t could be expected i n t h e downward d i r e c t i o n .

Assuming s t e a d y - s t a t e c o n d i t i o n s , t h e s a l t w i l l e v e n t u a l l y ad-

j u s t t o a cornposition whose BF3 p a r t i a l p r e s s u r e i s e q u a l t o t h e BF, p a r t i a l p r e s s u r e based on t h e g a s flows.

Therefore, i f w e m a i n t a i n proper

c o n t r o l of t h e s a l t temperature, t h e n c o n t r o l of t h e s a l t composition i s l i m i t e d only by t h e accuracy w i t h which w e can c o n t r o l t h e BF3 p a r t i a l p r e s s u r e of t h e cover gas.

I n an a c t u a l system, where t h e r e would b e

f i n i t e l i m i t s of e r r o r i n t h e c o n t r o l of s a l t temperatures and gas flows, it would probably ‘ce b e s t t o c o n t r o l t h e BF3 p a r t i a l p r e s s u r e w i t h a deliberate b i a s on t h e h i g h s i d e .

The r a t i o n a l e i s t h a t it i s un-

l i k e l y t h a t we w i l l be able t o c o n t r o l p r e c i s e l y a t t h e e u t e c t i c p o i n t ;

t h e r e f o r e we should t r y t o i n s u r e t h a t t h e normal d e v i a t i o n i s on t h e s i d e of i n c r e a s e d NaBF4 f r a c t i o n i n o r d e r t o g a i n t h e advantage of t h e lower i n c r e m e n t a l i n c r e a s e i n m e l t i n g p o i n t .

By r e f e r e n c e t o Fig. A . l

i n Appendix A, we n o t e t h a t t h e m e l t i n g p o i n t i n c r e a s e s an average of

$ between 92 and 90 mole '$ NaBF, , whereas t h e i n c r e a s e between 92 and 100 mole $ NaBF4 i s only 5.4"F/mole %. I n o r d e r t o examine t h e

23"F/mole

f e a s i b i l i t y of o p e r a t i n g with a b i a s i n BF,

p a r t i a l pressure, consider

a system i n which t h e mole f r a c t i o n of NaBF,

i s f and t h e temperature

of t h e s a l t a t t h e s a l t - g a s i n t e r f a c e i s 1150째F; a t o t a l g a s flow of Ft scfm i s flowing p a s t t h e s a l t - g a s i n t e r f a c e i n t h e pump bowl; t h e gas flow i s made up of a mixture of Fh scfm of helium and F scfm of BF,; b t h e gas p r e s s u r e i n t h e pump bowl i s maintained a t a v a l u e of Pt p s i a ; t h e p a r t i a l p r e s s u r e of BF,

i s Pb p s i a ; ( Pb)g r e p r e s e n t s t h e p a r t i a l

p r e s s u r e of BF3 based on gas flows,

and ( P ) r e p r e s e n t s t h e p a r t i a l p r e s s u r e of BF, based on t h e composition b s and temperature of t h e s a l t (see Appendix D ) :

(Pb), = ( 0 . 4 2 5 f ) / ( 1

f ) a t 1150째F

W e would l i k e t o know how t h e s a l t composition i s a f f e c t e d when we s e t

t h e gas flows s o t h a t t h e y correspond t o a v a l u e of ( P ) t h a t i s b g s l i g h t l y h i g h e r t h a n t h e i d e a l v a l u e f o r (Pb),. W e f i r s t set ( P ) (P )

bff

, then

and f i n a l l y we d i f f e r e n t i a t e we s o l v e f o r f i n terms of F b' t o determine how f i s a f f e c t e d by a change i n Fb: b s

If we assume t h a t Pt and Fh are c o n s t a n t a t 30 p s i a and 0.5 scfm, respec-

tively,* then 30Fb f =

30.425Fb

0.21

and 6.30 ( a f / a F b ) T = -(30.425Fb + 0.21)' If we assume a v a l u e of

5 p s i f o r t h e BF, p a r t i a l p r e s s u r e (Appendix

A, Fig. A.2, e u t e c t i c composition a t l150째F), we can estimate $he i d e a l v a l u e f o r Fb by n o t i n g t h a t t h e r a t i o of gas flows i s e q u a l t o t h e r a t i o of p a r t i a l p r e s s u r e s :

from which F-

0.1

and ( a f / a F ) = 0.6 f o r Fb = 0.1. W e conclude from t h i s t h a t a r e a s o n a b l e b T b i a s i n t h e BF, flow w i l l r e s u l t i n an a c c e p t a b l e s h i f t i n t h e s a l t composition.

For example, i f t h e S i a s i s 10% (aFb = 0.01), t h e composition

s h i f t , af, i s 0.006. I n o t h e r words, i f t h e BF, flow i s a d j u s t e d t o 10% h i g h e r t h a n t h e i d e a l v a l u e , assuming an i n i t i a l s a l t composition of 92

$ NaBF4, and t h e m e l t i n g p o i n t a t t h i s composition i s e s t i m a t e d t o be about 3'F

mole

NaBF,,

t h e composition w i l l s h i f t e v e n t u a l l y t o 92.6 mole

above t h e e u t e c t i c m e l t i n g p o i n t .

I n o r d e r t o d e s i g n a r e l i a b l e system f o r c o n t r o l l i n g t h e s a l t

composition by means of a BF:, overpressure, one must have r e l i a b l e i n formation r e g a r d i n g t h e BF,

p a r t i a l p r e s s u r e of t h e s a l t a t c o n c e n t r a t i o n s

and temperatures of i n t e r e s t . A and D and Refs. 2 and

Data have been p u b l i s h e d (see Appendices

5 ) t h a t provide mathematical s t a t e m e n t s r e l a t i n g

s a l t composition and temperature and BF, p a r t i a l p r e s s u r e , and t h e s e

*It i s estimated t h a t t h e s e v a l u e s are t y p i c a l of t h o s e t h a t might b e used i n an MSBR secondary c o o l a n t system.

r e l a t i o n s h i p s have been used i n t h e remarks under items 1 through

4 above.

However, t e s t work t h a t w a s performed t o i n v e s t i g a t e t h e pumping charact e r i s t i c s of t h e s a l t ( s e e S e c t . 5.1) i n d i c a t e d t h a t t h e BF,

p a r t i a l pres-

sure of t h e salt can b e a l t e r e d s i g n i f i c a n t l y by t h e presence of contaminants.

The r e s u l t s of t h o s e t e s t s i n d i c a t e d t h a t t h e p r e s s u r e of i n c i p i e n t

c a v i t a t i o n w a s about

16% h i g h e r f o r t h e f l u s h charge t h a n for t h e c l e a n

charge, and t h i s e f f e c t w a s a t t r i b u t e d t o t h e r e s i d u e , o r h e e l , t h a t r e mained i n t h e l o o p a f t e r d r a i n i n g out t h e o l d charge of BULT-4 s a l t .

W e

do not know t h a t t h e r e i s a one-to-one r e l a t i o n s h i p between c a v i t a t i o n p a r t i a l p r e s s u r e of t h e s a l t , b u t we assume t h a t t h e

p r e s s u r e and t h e BF,

r e l a t i o n s h i p i s d i r e c t and t h e r e f o r e t h e BF,

p a r t i a l p r e s s u r e of t h e f l u s h

charge must have been h i g h e r t h a n t h a t of t h e c l e a n charge. .

e f f e c t were p r e s e n t b u t not known, t h e BF,

If such an

p a r t i a l p r e s s u r e of t h e gas

f e e d would be i n a d v e r t e n t l y a d j u s t e d t o a v a l u e lower t h a n r e q u i r e d , and,

as i n d i c a t e d i n t h e d i s c u s s i o n s above, t h e NaBF4 f r a c t i o n of t h e s a l t would be reduced due t o t r a n s f e r of BF,

out of t h e s a l t .

Therefore, t h e

composition c o n t r o l system must be a b l e t o recognize t h e presence of contaminants and t h e n a t u r e and e x t e n t OP t h e i r e f f e c t on t h e BF,

partial

p r e s s u r e of t h e s a l t . I n summary,the consequences of a change i n s a l t composition can be s e r i o u s , b u t t h e k i n e t i c s of t h e system are such t h a t r a p i d change i s h i g h l y improbable.

W e should be a b l e t o u s e an a p p l i e d o v e r p r e s s u r e of

BF, t o c o n t r o l t h e composition w i t h i n d e s i r e d l i m i t s , provided we have available a s u i t a b l y a c c u r a t e method â&#x201A;Źor measuring t h e s a l t composition and t h e n e c e s s a r y d a t a r e l a t i n g t h e BF:, p a r t i a l p r e s s u r e of t h e s a l t b o t h

as a f u n c t i o n of t h e r a t i o of t h e primary c o n s t i t u e n t s , NaBF4 and NaF, and as a f u n c t i o n of probable contaminants, such as f u e l s a l t and c o r r o s i o n products.

The t e s t work c o n s i s t e d i n (1) o b t a i n i n g o p e r a t i n g

e x p e r i e n c e w i t h t h e BF, p a r t i a l p r e s s u r e c o n t r o l system and ( 2 ) e v a l u a t i n g s e v e r a l proposed methods f o r monitoring t h e composition of t h e

salt.

5.2.1 Operation of t h e BF, p a r t i a l p r e s s u r e c o n t r o l system The d a t a f u r n i s h e d by Cantor e t a1.5 were used t o make a p l o t of W

BF,

p a r t i a l p r e s s u r e v s s a l t temperature w i t h s a l t composition as a

parameter (Appendix A, F i g . A.2, and Appendix D )

The s a l t composition

w a s assumed t o be a t t h e e u t e c t i c p o i n t , NaBF4-NaF (92-8 mole $), and

t h e t a r g e t v a l u e o r c o n t r o l p o i n t f o r BF,

p a r t i a l pressure was obtained

from t h e p l o t by i n t e r p o l a t i n g a t t h e s p e c i f i e d s a l t temperature. t a r g e t v a l u e f o r t h e BF,

The

gas flow r a t e w a s t h e n calcul.ated by e q u a t i n g

t h e flow r a t i o t o t h e p r e s s u r e r a t i o :

where F i s t h e r e q u i r e d BF, gas flow, F i s t h e t o t a l gas flow, Pb i s b t t h e t a r g e t value f o r BF, p a r t i a l p r e s s u r e , and Pt i s t h e t o t a l gas p r e s -

sure a t t h e s u r f a c e of t h e s a l t . A g e n e r a l d e s c r i p t i o n of t h e gas system i s g i v e n i n S e c t i o n s 4.5 through

4.7.

H e l i u m w a s f e d i n t o t h e pump bowl i n t h r e e s e p a r a t e streams:

t h e s h a f t purge, which w a s h e l d c o n s t a n t a t 850 c$/min t o t h e pump s h a f t w a s 950 c$/min,

b u t 100 c$/min

( t h e t o t a l flow

w a s s p l i t o f f as t h e

lower seal purge stream); t h e p r e s s u r e t r a n s m i t t e r purge, which w a s h e l d c o n s t a n t a t 230 c$/min; t h e BF, tube.

and t h e mixed-gas helium, which w a s mixed w i t h

gas and f e d i n t o t h e pump bowl by way of t h e s a l t l e v e l bubbler The t o t a l flow t o t h e b u b k l e r t u b e , t h a t i s , helium p l u s BF,

h e l d c o n s t a n t a t 370 crr?/min, Ft, w a s constant at

, was

s o t h e t o t a l gas flow i n t o t h e pump bowl,

1450 c$/min.

The flow rate of helium t o t h e b u b b l e r

t u b e w a s o b t a i n e d by s u b t r a c t i n g t h e t a r g e t v a l u e f o r t h e BF,

gas flow

rate, Fb, from 370. The s e t p o i n t f o r t h e t o t a l p r e s s u r e , Pt, w a s somewhat a r b i t r a r y as long as a margin w a s provided above t h e p o i n t of c a v i t a t i o n i n c e p t i o n i n t h e pump.

T e s t d a t a (see S e c t . 5 . 1 ) i n d i c a t e d t h a t

a t t h e m a x i m u m a n t i c i p a t e d s a l t temperature of 1300째F t h e p r e s s u r e of i n c i p i e n t c a v i t a t i o n f o r t h e c l e a n charge w a s about

p s i g , and 5 p s i

w a s added t o t h i s f i g u r e t o o b t a i n a s e t p o i n t of 24 p s i g f o r Pt.

This

s e t t i n g provided a comfortable margin of 20 p s i when o p e r a t i n g a t t h e normal s a l t temperature of 1025째F.

It might b e noted t h a t t h e r e i s an

i n c e n t i v e t o o p e r a t e a t a h i g h t o t a l p r e s s u r e due t o t h e i n v e r s e e f f e c t on t h e BF, than

gas flow r a t e .

Also, t h e p r e s s u r e w a s set a t 24 p s i g , r a t h e r

23 o r 25, Secause 24 p s i g i s almost e x a c t l y e q u a l t o 2000 mm Hg

a b s o l u t e , and c a l c u l a t i o n s i n v o l v i n g m e t r i c u n i t s w e r e s i m p l i f i e d .

33 W

1025째F t h e i n d i c a t e d v a l u e f o r Pb i s 1.35 p s i a .

38.7 p s i a f o r Pt, and 1450 c$/min as t h e t a r g e t v a l u e f o r t h e BF,

for F

gas flow.

Using t h i s v a l u e f o r P b' we o b t a i n a v a l u e of 50 c$/min Except f o r b r i e f p e r i o d s ( l e s s

t h a n 10% of t o t a l c i r c u l a t i n g t i m e ) , when t h e s a l t w a s c i r c u l a t e d a t t e m p e r a t u r e s o t h e r t h a n lO25OF, and b r i e f s p e c i a l t e s t s t h a t r e q u i r e d varying t h e BFa flow, t h e t a r g e t v a l u e f o r c o n t r o l of t h e BF3 gas flow w a s h e l d c o n s t a n t at 50 c$ /min.

W e were unable t o e v a l u a t e t h e e f f e c t i v e n e s s of t h e BF,

p a r t i a l pres-

sure c o n t r o l system on t h e b a s i s of i t s u l t i m a t e o b j e c t i v e , t h a t f s , eont r o l of t h e s a l t composition, because we d i d not have an adequate method f o r measuring t h e s a l t composition (see S e c t . 5 . 2 . 2 ) .

Therefore, obser-

v a t i o n s concerning p a r t i a l p r e s s u r e c o n t r o l w i l l b e l i m i t e d t o some comments r e l a t i v e t o t h e accuracy of t h e gas flows ( Fb and Fh ) and t h e system overpressure ( P t ) and t o t h e mechanical r e l i a b i l i t y of t h e system. Zrne t h r e e gas streams t h a t made up t h e t o t a l flow of helium i n t o t h e system w e r e monitored e i t h e r w i t h c a p i l l a r y flow elements or ro5ameters.

The

c a l i b r a t i o n s of t h e flow instruments were checked b e f o r e , during, and

after t h e o p e r a t i o n of t h e f a c i l i t y u s i n g a bubble meter and a w e t t e s t meter.

Since t h e s e t e s t i n s t r u m e n t s are a c c u r a t e t o w i t h i n l%, we feel

t h a t t h e l i m i t of e r r o r i n t h e helium flow rate w a s of t h e same o r d e r ,

W e used t h e w e t t e s t meter, f i l l e d w i t h mineral o i l i n s t e a d of water, t o c a l i b r a t e t h e BF,

flow element u s i n g BF,

gas.

However, due t o t h e l i m i t a -

t i o n s of t h e w e t t e s t meter, we were unable t o o b t a i n r e a d i n g s below 200 c$/min,

and we could not use t h e bubble meter f o r flows between 0

and 200 c$/min

because of t h e s t r o n g a f f i n i t y between BFa and water.

a n a l t e r n a t i v e , w e c a l i b r a t e d t h e BF,

flow element w i t h argon u s i n g t h e

bubble meter and t h e n used t h e argon curve as a guide t o e x t r a p o l z 5 e t h e BF3 flow curve i n t o t h e low-flow r e g i o n , a t t e m p t i n g t o maintain t h e same r e l a k i v e s e p a r a t i o n between t h e curves ( i n t h e r e g i o n between 200 and 400 cm3/min, t h e BF,

flow w a s about 20% h i g h e r t h a n t h e argon flow f o r t h e

same s c a l e r e a d i n g ) .

Because of t h i s d i f f i c u l t y w i t h t h e c a l i b r a t i o n , t h e

BF, flow r e a d i n g s probably have a h i g h e r e r r o r l i m i t t h a n t h e helium r e a d i n g s , b u t w e f e e l t h a t an estimate of t h e BF3 flow e r r o r could conservat i v e l y b e p l a c e d a t less t h a n -C20$.

An attempt w a s made t o check t h e

accuracy of t h e BF3 flow s e t t i n g by comparison w i t h BF3 c y l i n d e r usage,

34 The following data on BF3 c y l i n d e r usage w e r e e x t r a c t e d from t h e o p e r a t i n g log :

Date Cylinder

On l i n e

Off line

1-6-69 4-28-69 8-15-69

4-28-69 8-15-69 1-27-70

3 4

The flow s e t t i n g f o r BF,

Salt circulating time (hr)

Cy1inder p r e s sure bop (Psi)

2323 2194 2463

1450 1300

1610

w a s h e l d c o n s t a n t a t 50 c S / m i n d u r i n g t h e

p e r i o d s covered by t h e above o p e r a t i n g data.

The BF3 c y l i n d e r data were

used t o estimate a n average BF, flow r a t e as follows:

where Fc = EF3 flow rate, dp/dt = average rate of drop i n c y l i n d e r p r e s s u r e , dN/dp = estimated mass of EF3 p e r p s i of c y l i n d e r p r e s s u r e ,

= s p e c i f i c volume of EF3 g a s .

Tne average v a l u e f o r dp/dt f o r a l l t h r e e c y l i n d e r s w a s 0.0104 p s i / min.

The s p e c i f i c volume of EF3 (Appendix A, S e c t .

A.4) i s 5.6 f t 3 / l b m .

The estimated mass of BF3 p e r c y l i n d e r ( t h e c y l i n d e r weights were not checked) w a s assumed t o b e somewhere between

59 and 62 l b m / p s i . The

lower f i g u r e w a s o b t a i n e d by d i v i d i n g t h e t o t a l mass of BFs,

as s t a t e d

on t h e purchase o r d e r , by t h e t o t a l number of c y l i n d e r s r e c e i v e d , t h a t

i s , 1000/17. The h i g h e r v a l u e w a s t h e nominal mass p e r c y l i n d e r as s t a t e d on t h e purchase o r d e r .

The corresponding v a l u e s f o r dM/dp,

and 0.0365 l b m / p s i , were o b t a i n e d by d i v i d i n g by t h e average p r e s s u r e f o r a f u l l c y l i n d e r .

1600 p s i g , which w a s

By i n s e r t i n g t h e i n d i c a t e d

v a l u e s i n t o t h e e q u a t i o n f o r Fc, w e g e t v a l u e s of t h e BF3 flow rate, or 20 and

0.0384

60 and 63 cm3/min f o r

26% above t h e t a r g e t v a l u e of 50 c$/min.

â&#x20AC;&#x2DC; J

35 W

This r e l a t i v e l y poor agreement between t h e BF, by t h e flow element and t h e BF,

flow r a t e as i n d i c a t e d

flow rate as i n d i c a t e d by t h e c y l i n d e r

d a t a may have been due t o t h e cumulative e f f e c t of s m a l l e r r o r s i n t h e

estimates f o r dp/dt and dM/dp and i n t h e t e c h n i q u e used f o r t h e c a l i b r a t i o n of t h e BF, a c t u a l l y been

c a p i l l a r y flow element.

If t h e BF,

flow rate had

63 cr?/min i n s t e a d of t h e i n t e n d e d 50 c$/min,

t h e n we

could p r e d i c t , u s i n g t h e method d e s c r i b e d i n S e c t i o n 5.2, t h a t t h e s a l t composition should have been s h i f t e d from 92 mole NaBF,

NaBF, t o 93.5 mole

and, o t h e r t h i n g s b e i n g e q u a l , t h i s would have caused a 25% i n -

c r e a s e i n t h e BF,

p a r t i a l pressure.

If t h e BF,

p a r t i a l p r e s s u r e had

a c t u a l l y s h i f t e d t h i s much, t h e r e should have been a s i g n i f i c a n t change i n t h e r e a d i n g on t h e thermal c o n d u c t i v i t y c e l l t h a t w a s b e i n g used t o monitor t h e o f f - g a s steam. clude t h a t t h e BF,

Since no such change w a s observed, we con-

flow as c a l c u l a t e d from t h e c y l i n d e r usage data w a s

probably i n e r r o r on t h e h i g h s i d e . I n a d d i t i o n t o t h e c o n t r o l of t h e gas flows, performance of t h e BF, p a r t i a l p r e s s u r e c o n t r o l system r e q u i r e s r e l i a b l e c o n t r o l of t h e t o t a l system o v e r p r e s s u r e ( P )

An e r r o r i n t h e i n d i c a t i o n of t o t a l p r e s s u r e

w i l l cause a n e r r o r i n t h e c a l c u l a t i o n of t h e BF,

gas flow s e t t i n g , and

t h e s a l t composition would t h u s not be c o n t r o l l e d a t t h e d e s f r e d p o i n t .

A s an example, suppose t h a t t h e s a l t composition and temperature a r e p a r t i a l p r e s s u r e ( P ) i s 5 p s i , and 25 p s i a has been b s e l e c t e d as t h e set p o i n t f o r t o t a l o v e r p r e s s u r e ( P ) Since Fb/Ft = such that; t h e BF,

Pb/Pt flow.

= 5/25 = 0 . 2 , t h e

s e t p o i n t f o r BF, flow i s 20% of t h e t o t a l gas

Suppose, however, t h a t t h e p r e s s u r e i n d i c a t o r i s i n e r r o r , such

t h a t t h e t o t a l o v e r p r e s s u r e i s a c t u a l l y 20 p s i a . p r e s s u r e of BF,

Since t h e p a r t i a l

5 p s i , t h i s means t h a t t h e composition of t h e gas

phase, and l i k e w i s e t h e composition of t h e o f f - g a s stream, i s 25% BF,.

A s a r e s u l t , we are f e e d i n g a 20% mixture and removing a 25% mixture, and t h e s a l t w i l l b e d e p l e t e d i n NaBF4 u n t i l t h e composition of t h e o f f - g a s stream i s reduced t o 20%.

During t h e o p e r a t i o n of t h e f a c i l i t y ,

t h e p r e s s u r e i n s t r u m e n t s were c a l i b r a t e d a g a i n s t a master gage such t h a t t h e e r r o r l i m i t i n t o t a l p r e s s u r e i n d i c a t i o n could b e c o n s e r v a t i v e l y e s t i m a t e d t o be less t h a n 50.5 p s i .

Using t h e normal o p e r a t i n g c o n d i t i o n s

of 1.35 p s i f o r Pb and 38.7 p s i a f o r P

tâ&#x20AC;&#x2122;

t h e r a t i o of BF,

flow i s c a l c u l a t e d t o be 1.35/38.7 o r 3.49%.

flow t o t o t a l

If we assume t h a t t h e

t o t a l p r e s s u r e w a s low by 0.5 p s i , o r 38.2 p s i a , w e can c a l c u l a t e t h a t t h e gas phase, and t h e off-gas stream, w a s a c t u a l l y 1.35/38.2 o r 3.5476, and BF, would have been removed from t h e s a l t u n t i l t h e p a r t i a l p r e s s u r e

of BF3 over t h e s a l t w a s reduced t o (0.0349)(38.2) or 1.33 p s i . r e d u c t i o n of 0.02 p s i i n BF,

This

p a r t i a l p r e s s u r e would have corresponded

t o a r e d u c t i o n of t h e NaBF4 mole f r a c t i o n of t h e s a l t from 92 t o 91.9%. W e conclude from t h i s t h a t t h e t o t a l p r e s s u r e i n d i c a t i o n d u r i n g t h e op-

e r a t i o n of t h e f a c i l i t y w a s a c c u r a t e enough t h a t a n e g l i g i b l e r e d u c t i o n i n s a l t composition would have occurred even i f t h e p r e s s u r e i n d i c a t i o n had been low by t h e m a x i m u m e s t i m a t e d l i m i t of e r r o r . From a mechanical s t a n d p o i n t , t h e o p e r a t i o n of t h e BF, p r e s s u r e c o n t r o l system w a s e s s e n t i a l l y t r o u b l e free.

partial

As one would ex-

p e c t , no problems a t a l l w e r e encountered w i t h t h o s e p o r t i o n s of t h e system t h a t contained only helium.

The BF,

flow c o n t r o l system o p e r a t e d

adequately, although t h e r e were o c c a s i o n a l p e r i o d s of n o i s e o r hash on t h e BF3 flow r e c o r d e r , i n d i c a t i n g t h a t t h e flow c o n t r o l l e r w a s responding sluggishly.

We a t t r i b u t e d t h i s t r o u b l e t o accumulation i n t h e c o n t r o l l e r

o r i f i c e of t h e t y p i c a l f l u i d t h a t r e s u l t s when m o i s t u r e ( o r moist a i r ) i s i n t r o d u c e d i n t o a system c o n t a i n i n g BF,.

The p r e s s u r e t r a n s m i t t e r

t h a t w a s used t o i n d i c a t e t h e t o t a l system o v e r p r e s s u r e performed q u i t e satisfactorily.

A s noted i n the design d e s c r i p t i o n , a continuous helium

purge stream w a s maintained i c t h e t r a n s m i t t e r l i n e i n o r d e r t o minimize t h e c o n c e n t r a t i o n of BF,

i n t h e v i c i n i t y of t h e t r a n s m i t t e r diaphragm.

No t e s t s were made, however, t o oâ&#x20AC;&#x2122;.3tain a d i r e c t measure of t h e e f f e c t i v e ness of t h i s purge stream. 5.2.2

Methods f o r monitoring s a l t composition Four methods were considered f o r monitoring t h e composition of t h e

salt. 1. Chemical a n a l y s e s of s a l t samples.

I n t h i s method t h e b a s i c

c o n s t i t u e n t s are determined from chemical a n a l y s e s , and t h e n t h e mole

A p r e l i m i n a r y mathemtitical a n a l y s i s i n d i c a t e d t h a t t h e l i m i t s of e r r o r of t h e chemical f r a c t i o n i s i n f e r r e d from s t o i c h i o m e t r i c r a t i o s .

37 a n a l y s e s were t o o g r e a t t o permit u s e of t h i s method.

This c o n c l u s i o n

w a s v e r i f i e d by a p l o t o f t h e mole f r a c t i o n as c a l c u l a t e d from a n a l y s e s of a l a r g e number of s a l t samples t a k e n d u r i n g o p e r a t i o n of t h e t e s t f a c i l i t y (see F i g . 1.3). 2.

Change i n h e a t t r a n s f e r c o e f f i c i e n t due t o a s a l t d e p o s i t .

h e a t t r a n s f e r s u r f a c e i n t h e s a l t stream would be c o n t r o l l e d a t a t e m p e r a t u r e s l i g h t l y above t h e normal l i q u i d u s t e m p e r a t u r e .

A change i n

composition would r e s u l t i n a d e p o s i t on t h e c o o l s u r f a c e t h a t could be d e t e c t e d by a change i n h e a t t r a n s f e r c o e f f i c i e n t .

It w a s concluded

t h a t p r e f e r e n t i a l d e p o s i t i o n of c o r r o s i o n p r o d u c t s would make t h i s method d i f f i c u l t t o i n t e r p r e t .

D i f f e r e n t i a l thermal a n a l y s i s .

I n t h i s method t h e composition

i s i n f e r r e d from a n a l y s i s of temperature p r o f i l e s o b t a i n e d by moving a

s a l t sample through c a r e f u l . l y c o n t r o l l e d freeze and thaw c y c l e s .

Al-

though t h i s method may be a p p l i c a b l e , it w a s not e v a l u a t e d because it r e q u i r e d s p e c i a l i z e d sampling t e c h n i q u e s t h a t were o u t s i d e t h e c a p a b i l i t y of t h e t e s t f a c i l i t y .

Thermal c o n d u c t i v i t y of o f f - g a s stream.

t o c o n t a i n t h e e q u i l i b r i u m c o n c e n t r a t i o n of BF,

The o f f - g a s i s assumed f o r t h e given s a l t t e m -

p e r a t u r e and c o r n p ~ s i t i o n . ~ ~The off'-gas stream i s monitored c o n t i n u o u s l y by a t h e r m a l c o n d u c t i v i t y c e l l ( F i g . BF3.

14), which

i s c a l i b r a t e d i n percent

i s c a l c u l a t e d u s i n g t h e t h e r m a l conduc-

The p a r t i a l p r e s s u r e of BF,

t i v i t y c e l l r e a d i n g and t h e t o t a l o v e r p r e s s u r e as i n d i c a t e d by a p r e s s u r e transmitter.

This v a l u e for BF,

p a r t i a l p r e s s u r e i s t h e n compared with

t h e t h e o r e t i c a l v a l u e f o r t h e e u t e c t i c composition as c a l c u l a t e d from an e q u a t i o n of t h e f o l l o w i n g form (Appendix D ) : In P =

16.837 - 24,540 T '

where P i s p a r t i a l p r e s s u r e o f BF,

( p s i ) and T i s temperature ( OR).

The t h e r m a l c o n d u c t i v i t y c e l l i n c o r p o r a t e s a Wheatstone b r i d g e , w i t h one l e g c o n t a i n i n g a c o n d u c t i v i t y element t h a t i s exposed t o a r e f e r e n c e gas.

"he second l e g h a s a similar element t h a t i s normally exposed t o

t h e sample gas, and t h e o u t p u t v o l t a g e i s a f u n c t i o n of t h e d i f f e r e n c e i n t h e r m a l c o n d u c t i v i t y between t h e r e f e r e n c e and sample g a s e s .

A zero

ORNL-DWG 69-5494

CALCULATED FROM 0

RATIO OF B TO No RATIO

OF F TO B

EQUATION 2 . + 2 6 * (B/No)

4/{[0.569*

(F/B)]-3}

80 0

F i g . 13.

20 40 60 CIRCULATING TIME (days)

io0

Mole f r a c t i o n XaBF4 c a l c u l a t e d from s a l t sample a n a l y s e s .

OR\-

DWG 7 2 - 2 0 8 0

100 Crn3/rnI"

S'APOR

SPACE = -I i t 3 . I

Ts =

AREA OF SALT

SURFACE = - 3 f t 2

Fig. tion.

SAL'

IEMPERATLJRE

= S N C COVPOSITION

14. Schematic diagram of monitoring system f o r

s a l t composi-

40 o r background r e a d i n g i s obtained by t e m p o r a r i l y exposing b o t h l e g s t o t h e reference gas.

I n t h e t e s t f a c i l i t y , t h e r e f e r e n c e gas w a s helium

and t h e sample gas c o n s i s t e d of a mixture of BF3 and helium, with t h e BF,

c o n c e n t r a t i o n normally between 0 and 5 v o l

The a p p l i c a b i l i t y of

t h e thermal c o n d u c t i v i t y method depends on t h e r e b e i n g a s i g n i f i c a n t d i f f e r e n c e between t h e tnerrnal c o n d u c t i v i t i e s of t h e r e f e r e n c e and sample gases and on a p r e d i c t a b l e r e l a t i o n s h i p between t h e thermal c o n d u c t i v i t y and composition of t h e sample g a s . Evaluation of t h e thermal c o n d u c t i v i t y method

5.2.3

I n o r d e r t o examine t h e a p p l i c a b i l i t y of t h e thermal c o n d u c t i v i t y method f o r monitoring t h e s a l t composition, we must c o n s i d e r a t least four questions.

1. Is t h e SF, p a r t i a l p r e s s u r e a r e l i a b l e i n d i c a t o r of t h e s a l t composition? 2.

Is t h e o f f - g a s stream i n eqGilibrilun with t h e s a l t ?

Is t h e thermal conductivit;; o f t h e gas a r e l i a b l e measure of

t h e EF3 p a r t i a l p r e s s c r e ?

Is t h e v a r i a t i o n of' W3 p a r t i a l p r e s s m e w i t h s a l t composition

reasonable wken compared w i t ! e r r o r s t h a t might i e expected i n t h e measurement of s a l t temperature, t o t a l overpressure, and BF,

concentration?

X i t F A r e g a r d t o t k e i'irst q z e s t i o n , experimental work2 h a s keen p e r -

formed t o determine th-e v a r i a t i o n -retween s a l t composition, s a l t t e m p e r a t u r e , and

press-;re

T!lese

r e l a t i o n s h i p s maJ- n o t be r e l i a b l e ,

kowever, i f contaminazts zre p r e s e x t i n t h e s a l t .

W e know from e x p e r i -

ence during t h e c a v i t a t i o n t e s t s (see S e c t . 5.1) t h a t r e l a t i v e l y s m a l l amounts of f u e l s a l t added t o t k e f l u o r o l - o r a t e s a l t can cause changes which- imply t h a t t h e 8F3 p a r t i a l p r e s s u r e has 'seen s i g n i f i c a n t l y a f f e c t e d .

For example, t h e c a v i t a t i o n p r e s s u r e oi' t h e contaminated s a l t a t 1150째F i s t h e same as t h a t of t h e c l e a n s a l t a t 1210째F. Unfortunately, t h e r m a l

c o n d u c t i v i t y c e l l data f'ron; t h e f l u s h s a l t o p e r a t i n g p e r i o d are i n s u f f i c i e n t t o determine whether t h e r e w a s a d e t e c t a - z l e change i n t h e t h e r m a l c o n d u c t i v i t y of t h e o f f - g a s stream.

A d d i t i o n a l experimental work i s

needed t o show t h e v a r i a t i o n of EF3 p a r t i a l p r e s s u r e as a f u n c t i o n of t h e c o n c e n t r a t i o n of any contaminant t h a t might be p r e s e n t o r t h a t might be

41 W

expected t o l e a k i n t o t h e f l u o r o b o r a t e s a l t .

Depending on t h e r e s u l t s

of t h i s work, we may need (1) t o develop procedures f o r p u r i f y i n g t h e f l u o r o b o r a t e s a l t ; ( 2 ) t o a r r a n g e t h e d e s i g n t o prevent e n t r y of t h e contaminants i n t o t h e s a l t ; ( 3 ) t o provide a monitoring system whereby

we can monitor, and a d j u s t f o r , t h e contaminant l e v e l ; or ( 4 ) t h e e f f e c t s may be minor enough s o t h a t no a c t i o n i s n e c e s s a r y . Q u e s t i o n 2 has t o do w i t h t h e problem of a s s u r i n g o u r s e l v e s t h a t t h e gas sample w e are looking a t i s t r u l y r e p r e s e n t a t i v e of t h e e q u i l i b r i u m p a r t i a l p r e s s u r e of BF3 a t t h e s u r f a c e of t h e s a l t .

I n t h e test f a c i l i t y ,

helium and BF3 were added continuously t o t h e system a t c o n t r o l l e d flow

rates; t h e s h a f t purge and p r e s s u r e t r a n s m i t t e r purge streams were vented d i r e c t l y i n t o t h e pump bowl vapor space, while t h e BF3 and mixed-gas helium were i n t r o d u c e d a f e w inches below t h e s u r f a c e of t h e s a l t f n t h e pump bowl.

An e q u i v a l e n t amount of off-gas

(1450 c$/min)

w a s vented

continuously by t h e p r e s s u r e c o n t r o l v a l v e s o as t o h o l d t h e system p r e s sure c o n s t a n t .

The stream t h a t w a s monitored by t h e thermal c o n d x t i v i t y

c e l l w a s a 100-cm3/min sample flow t a k e n from t h e o f f - g a s l i n e a t a p o i n t about 25 f t dGwnstream from t h e pump bowl, t h a t i s , j u s t upstream of t h e pressure control valve.

If t h e p a r t i a l p r e s s u r e of t h e BF3 i n t h e gas

f e e d were e q u a l t o t h e e q u i l i b r i u m p a r t i a l p r e s s u r e of BF3 over t h e s a l t , t h e n t h e r e should be no n e t t r a n s f e r of BF3 between t h e vapor space and t h e s a l t , and t h e o f f - g a s stream should r e p r e s e n t t h e composition of t h e

salt.

If t h e p a r t i a l p r e s s u r e of t h e

BF, i n t h e gas f e e d were not e q u a l

t o t h e e q u i l i b r i u m p a r t i a l p r e s s u r e of t h e BF3 over t h e s a l t , t h e n t h e r e would t e n d t o b e a t r a n s f e r of BF, between t h e s a l t and t h e vapor space. The d i r e c t i o n and rate of t h i s t r a n s f e r would depend on c o n c e n t r a t i o n d i f f e r e n c e , s u r f a c e area, temperature, gas r e s i d e n c e t i m e , etx., and it would b e t h e o r e t i c a l l y p o s s i b l e f o r t h e o f f - g a s stream t o r e p r e s e n t t h e gas f e e d composition, t h e salt composition, o r some i n t e r m e d i a t e v a l u e . Conditions i n t h e t e s t f a c i l i t y were f a v o r a b l e t o t h e i d e a l s i t u a t i o n ; t h a t i s , it appeared probable t h a t t h e gas space, and hence t h e o f f - g a s

stream, would t e n d t o b e i n e q u i l i b r i u m w i t h t h e s a l t .

For example, t h e

r e s i d e n c e t i m e f o r t h e gas was long (20 min), t h e c o n t a c t s u r f a c e w a s 2

r e l a t i v e l y l a r g e ( 3 f t ), and t h e r e w a s a good exchange of f l u i d (es;imated a t 15 gpm or one l o o p volume every 2 min) between t h e main l o o p

and t h e pump bowl s a l t pool.

S e v e r a l experiments were r u n i n a n attempt

t o determine i f t h e composition of t h e thermal c o n d u c t i v i t y c e l l sample

stream w a s r e p r e s e n t a t i v e of t h e gas composition t h a t would b e p r e d i c t e d from t h e s a l t composition and temperature.

These t e s t s are d e s c r i b e d

below, and t e s t results are summarized i n Table

I n a l l cases t h e test

p e r i o d w a s s h o r t (<8 h r ) , and it w a s assumed t h a t t h e s a l t composition w a s a t t h e e u t e c t i c and remained e s s e n t i a l l y c o n s t a n t . 1. Change i n s a l t temperature.

s a l t temperature c o n s t a n t , t h e BF,

With gas flow, t o t a l p r e s s u r e , and

c o n c e n t r a t i o n of t h e o f f - g a s stream

w a s determined from t h e thermal c o n d u c t i v i t y c e l l r e a d i n g .

The s a l t t e m -

p e r a t u r e w a s t h e n changed, and t h e c o n c e n t r a t i o n w a s a g a i n determined from t h e t h e r m a l c o n d u c t i v i t y c e l l . with t h e calculated values. intervals:

The measured v a l u e s were compared

The t e s t w a s performed over two temperature

9lO t o 1025°F and 1025 t o 1150°F. The agreement was only

f a i r i n t h e f i r s t c a s e and v e r y good i n t h e second case.

Change i n t o t a l p r e s s u r e .

With gas feed (1450 c$/min)

and

s a l t temperature (lo25OF) c o n s t a n t , t h e t o t a l p r e s s u r e w a s l e v e l e d out

a t 30 p s i a , and a t h e r m a l c o n d u c t i v i t y c e l l r e a d i n g w a s o b t a i n e d a t t h i s condition.

The t o t a l p r e s s u r e w a s t h e n i n c r e a s e d from 30 t o

p s i a i n about 12 m l r by c l o s i n g t h e p r e s s u r e c o n t r o l v a l v e .

The thermal

c o n d u c t i v i t y c e l l r e a d i a g w a s agair_ recorded a f t e r t h e system had l e v e l e d out a t t h e h i g h e r p r e s s u r e . r a t i o Pb/Pt,

Since nothing w a s done t o change Pb, t h e

and hence t h e EF3 c o n c e n t r a t i o n f r a c t i o n , would b e expected

t o d e c r e a s e ‘cy a l’actor of 2/3 i n o r d e r t o compensate f o r t h e f a c t o r of 3/2 by which t h e p r e s s u r e i n c r e a s e d .

Also, i f t h e t h e r m a l c o n d u c t i v i t y

c e l l were p r o p e r l y r e s p o n s i v e t o t h e change i n BF, c o n c e n t r a t i o n , i t s r e a d i n g should show a corresponding d e c r e a s e .

The thermal c o n d u c t i v i t y

c e l l responded as expected, showing a drop from

Change i n gas flow.

If t h e BF,

0.9 t o 0 . 6 M V .

c o n c e n t r a t i o n i n t h e vapor phase

over t h e s a l t were dependent on F /F o r i f t h e r e were a t i m e l a g i n 7: t’ r e t u r n i n g t o e q u i l i b r i u m , t h e n t h e thermal c o n d u c t i v i t y c e l l should show

a response t o a change i n t h e BF3/He flow r a t i o .

With a l l c o n d i t i o n s

c o n s t a n t , a r e a d i n g of BF, c o n c e n t r a t i o n w a s o b t a i n e d on t h e thermal conductivity c e l l .

Sudden changes were t h e n made i n t h e gas flow r a t i o .

I n one c a s e t h e BF, gas flow w a s i n c r e a s e d enough t o t r i p l e t h e normal

Table 4 . Effect of changes i n loop operating v a r i a b l e s on methods of estimating BF, p a r t i a l pressure ~~

Variable conditions Date of Test

Const ant conditions

Start

Variable

Finish

Salt tenperatwe

(OF)

8-30-68 9-26-68 6-6-69 8-30-68

Total pressnre

(psis)

44.7 44.7

Salt temperature, "F

910

1025

S a l t temperature, "F

1025

1150

T o t a l pressure, p s i a

29.7

44.7

io25

Gas flow r a t i o Gas flow r a t i o

0.04

0'17

910

G a s flow ratio (F~/F~)

0.043 0.043 0.033

Change i n thermal conductivity c e l l reading (Mv)

0.32

1.95

Change i n BF,

a.7 +3.8

p a r t i a l pressure ( p s i ) Thermal conductivity ~ cellb

~ G

+1 .o

+3.5

0.3

+5.8 -1.8

0.04

0.0

1025

44.7 44.7

10-15-68

Gas flow r a t i o with BF3 e n t e r i n g vapor space

0.04

0.10

1025

44.7

+3.7

10-16-68

Gas flow r a t i o with BF, e n t e r i n g vapor space

0.04

0.13

1025

44.7

+4.0

8-30-68

a S a l t temperature:

P, = exp(lh.83

bGas composition and pressure: 'Gas

feed flow r a t i o :

- (24,540/T, OR) =

psi.

(thermal conductivity c e l l readirLg) ( c a l i t r a t i o s f a c t o r ) ( t o t a l p r e s s s r e ) .

Pb = ( t o t a l p r e s s u r e ) (Fb/Ft)

~~ o

c o n c e n t r a t i o n ; i n a n o t h e r t e s t , t h e flow w a s c u t o f f completely.

The

flow v a r i a t i o n t e s t s w e r e t h e n r e p e a t e d w i t h t h e BF3 flow admitted d i r e c t l y t o t h e pump bowl vapor phase r a t h e r t h a n under t h e s a l t s u r f a c e .

No response w a s noted on t h e t h e r m a l c o n d u c t i v i t y c e l l during any of t h e flow v a r i a t i o n t e s t s .

It w a s concluded from t h e s e t e s t s t h a t t h e o f f - g a s stream from t h e t e s t f a c i l i t y w a s a r e l i a b l e i n d i c a t o r of t h e composition of t h e gas i n t h e pump bowl vapor space, and i n c a s e s where t h e BF, p a r t i a l p r e s s u r e based on t h e composition of t h e g a s f e e d w a s d i f f e r e n t from t h e BF, p a r t i a l p r e s s u r e based on t h e s a l t cornposition and temperature, t h e n t h e vapor space composition tended t o b e t h a t d i c t a t e d by t h e s a l t composition and t e m p e r a t u r e .

Reactor systems u s i n g pumps of similar d e s i g n and

s i m i l a r o p e r a t i n g c o n d i t i o n s should perform i n a s i m i l a r manner.

I n using

a sample p o i n t t h a t i s remote from t h e pump bowl o u t l e t , however, precautions must be taken t o insure t h a t t h e composition of the gas i s not i n a d v e r t e n t l y changed d u r i n g i t s passage from t h e pump bowl o u t l e t t o t h e thermal c o n d u c t i v i t y c e l l . Question

3 concerns a weakness i n t h e u s e of t h e thermal c o n d u c t i v i t y

c e l l as an i n d i c a t o r of BF,

concentration.

If t h e t h e r m a l c o n d u c t i v i t y

c e l l i s working p r o p e r l y , it w i l l respond t o any change i n t h e t h e r m a l c o n d u c t i v i t y of t h e gas whether t h a t change has been caused by a change i n t h e c o n c e n t r a t i o c of t n e SF3 o r by t h e a d d i t i o n or removal of some o t h e r material.

I n t h e des$-

and o p e r a t i o n of t h e system, t h e r e f o r e ,

precaEtions must Le t a k e n t o exclude, or t o d e t e c t and account f o r , any materials t h a t might g i v e a false s i g n a l .

Experimental work i s needed

t o i n v e s t i g a t e t h e v a r i a t i o n i n thermal c o n d u c t i v i t y c e l l r e a d i n g as a f u n c t i o n of t h e c o n c e n t r a t i o n of probable contaminants.

The f o u r t h q u e s t i o n i s concerned w i t h probable e r r o r s i n t h e measurement o f s a l t temperature and g a s p r e s s u r e and t h e e f f e c t such e r r o r l i m i t s might have on t h e u s e f u l n e s s of t h e thermal c o n d u c t i v i t y c e l l method.

W e s t a r t by r e f e r r i n g t o t h e g e n e r a l e q u a t i o n f o r BF, decompo-

s i t i o n p r e s s u r e , which i n c l u d e s t h e e f f e c t s of composition change as

w e l l as temperature change (Appendix D ) :

45 W

where Pb i s p a r t i a l p r e s s u r e of BF,

T i s temperature (

( p s i ) , f i s mole f r a c t i o n NaBF4, and

D i f f e r e n t i a t i n g a l t e r n a t e l y with r e s p e c t t o compo-

O R ) .

s i t i o n and temperature, w e g e t

Assuming v a l u e s of 1025 and 1150°F f o r s a l t temperature and 0.91, 0.92, and 0.93 f o r mole f r a c t i o n NaBF4, t h e c a l c u l a t e d v a l u e s f o r p a r t i a l p r e s s u r e and for r a t e of change of p a r t i a l p r e s s u r e a r e as shown i n Table 5 .

A t 1150°F a change i n composition from 0.92 ( t h e d e s i r e d v a l u e ) t o 0.91 would cause a change i n p a r t i a l p r e s s u r e of about 0.6 p s i .

The tempera-

ture e r r o r r e q u i r e d t o cause an apparent change of t h e same magnitude

or zbout 13°F.

would be 0.60/0.047,

measurement i s O . 5 % , o r about 6°F. g r e a t e r t h a n 0 . 5 mole

The expected accuracy of temperature

From t h i s we conclude t h a t changes

should not be masked by temperature e r r o r .

The apparent rate of change of BF, p a r t i a l p r e s s u r e as a f u n c t i o n of t o t a l p r e s s u r e i s numerically e q u a l t o t h e c o n c e n t r a t i o n f r a c t i o n

($ BF3/100), assuming c o n s t a n t gas flows: Pb = from which "b'

/ dPt=

F /F = Pb/Pt b t

Assuming a t o t a l p r e s s u r e of 24 p s i g , t h e c o n c e n t r a t i o n f r a c t i o n a t

1150°F (Pb

4.93 p s i ) would

4.93/38.7, or 0.13.

The e r r o r i n t o t a l

p r e s s u r e r e a d i n g r e q u i r e d t o cause an apparent change of 1 mole composition would t h e r e f o r e be: dPb/df -=a= 0*67 5 . 1 psi/mole %

Table

T, S a l t temperature ( OF) ~~

1025

1150

V a r i a t i o n o f BF, p a r t i a l p r e s s u r e with composition and temperature

f , Mole

fraction NaBF4

Rate of change of p a r t i a l pressure

'b? BF3 partial p r e s sure (Psi)

eT, E r r o r i n temperature r e q u i r e d t o produce a n a p p a r e n t composition change of 1 mole $J ( OF)

apb/a f (psi/mole $)

aPb/aT (PSI/ OR)

0.24 0.18

0.018

0.92

1.58 1.36

0.015

0.91

1.20

0.15

0.013

0.93 0.92

3 .(I9

4.93

0.87 0.67

0.91

4.33,

0.53

0.054 0.047 0.041

11.5 16 14

0 -93

I n P'0 = h ( -n +) 14.395

- 24, $40

psi,

47 W

38.7 p s i a , we should be a b l e t o r e a d p r e s s u r e w i t h i n 0.5 p s i , s o e r r o r

i n measurement of t o t a l p r e s s u r e should not be an important f a c t o r . The accuracy of t h e t h e r m a l c o n d u c t i v i t y c e l l readout should not be an important f a c t o r i n t h e d i s c u s s i o n because t h e r e a d i n g i s only relat i v e , t h a t i s , t h e instrument compares t h e c o n d u c t i v i t y of t h e gas mixture w i t h t h a t of a r e f e r e n c e gas, and p r o v i s i o n can be made f o r c o n t i n u a l c a l i b r a t i o n checks using mixtures of BF, and helium of known composition. There should l i k e w i s e be no problem i n d e s i g n i n g a thermal c o n d u c t i v i t y system t h a t w i l l have t h e d e s i r e d degree of s e n s i t i v i t y , t h a t i s , one t h a t will be a b l e t o see s m a l l enough changes i n s a l t composition.

For

example, i n t h e t e s t f a c i l i t y , t h e s e n s i t i v i t y of t h e thermal c o n d u c t i v i t y

4.3% BF, p e r m i l l i v o l t , t h a t i s , f o r a given reading, R, i n mV, t h e c o n c e n t r a t i o n , C, i n % BF3, w a s e q u a l t o 4.3R. If we l e t t h e concenc e l l was

t r a t i o n f r a c t i o n e q u a l f c , and n o t i n g t h a t f c = Pb/Pt, f c = C/100 = 4.3R/100 = Pb/Pt

then:

Solving f o r R i n terms of P and d i f f e r e n t i a t i n g , we o b t a i n t h e rate of b change of t h e thermal c o n d u c t i v i t y c e l l r e a d i n g as a f u n c t i o n of t h e BF, p a r t i a l pressure :

R = 23.25Pb/Pt

dR/dPb = 23.25/Pt m V / p s i

The rate of change of t h e r m a l c o n d u c t i v i t y c e l l r e a d i n g as a f u n c t i o n of s a l t composition can be o b t a i n e d by m u l t i p l y i n g by dPb/df, t h a t i s , t h e

rate of change of BF, p a r t i a l p r e s s u r e as a f u n c t i o n of salt composition: dR/df = (dPb/df)(dR/dPb) mV/mole

â&#x20AC;&#x2122;$

For t h e t e s t f a c i l i t y , where P w a s 38.7 p s i a , t h e change i n r e a d i n g as t a f u n c t i o n of BF3 p a r t i a l p r e s s u r e w a s 23.25/38.7, or 0.6 mV/psi. From Table 5, we n o t e t h a t a t 1025Â°F and f = 0.92, dPb/df has a v a l u e of 0.18; s o f o r t h i s c o n d i t i o n t h e v a l u e of dR/df W

(0.6)(0.18)

= 0.11 mV/mole

48 The smallest change i n thermal c o n d u c t i v i t y c e l l r e a d i n g t h a t could be considered s i g n i f i c a n t w a s about 0.05 mV, which w a s e q u i v a l e n t t o a change of about 0.5 mole

The u n i t i n s t a l l e d a t t h e t e s t f a c i l i t y ,

however, w a s an old-fashioned u n i t , and improved c e l l s are now a v a i l a b l e w i t h s e n s i t i v i t i e s t h a t are h i g h e r by a t least a f a c t o r of 10.

It might

b e noted t h a t t h e rate of change i n p a r t i a l p r e s s u r e as a f u n c t i o n of s a l t composition i n c r e a s e s as t h e s a l t temperature i n c r e a s e s , s o t h a t

t h e t e s t f a c i l i t y u n i t would probably have been adequately s e n s i t i v e for

For example, t h e MSBR i s expected t o o p e r a t e a t a s a l t temperature of 1150째F and a t o t a l overpressure of 30 p s i a . A t t h e s e conan MSBR system.

d i t i o n s , t h e v a l u e of dR/df f o r t h e t e s t f a c i l i t y u n i t would b e mole

and a change i n t h e s a l t composition of 0.13 mole

been d i s c e r n i b l e .

0 . 4 mV/

'$ should have

It might a l s o be noted t h a t t h e t e s t f a c i l i t y u n i t w a s

monitoring a mixture of helium and BF3, and t h e s e n s i t i v i t y of t h e u n i t w a s d i r e c t l y r e l z t e d t o t h e d i f f e r e n c e i n thermal c o n d u c t i v i t y c e l l

s i g n i f i c a n t l y , or it could rule out a l t o g e t h e r t h e use of t h e thermal c o n d u c t i v i t y method. I n summarjr, we conclude t h a t f o r systems which are similar i n des i g n and o p e r a t i n g c o n d i t i o n s t o t h e t e s t f a c i l i t y , we should be able t o monitor t h e composition of a c i r c u l a t i n g f l u o r o b o r a t e s a l t system by u s i n g a thermal c o n d u c t i v i t y c e l l t o monitor t h e g a s stream t h a t i s flowing from t h e vapor space which i s i n c o n t a c t w i t h t h e s a l t s u r f a c e .

5.3

Corrosion Product Deposition

During extended p e r i o d s of s a l t c i r c u l a t i o n , one or more of t h e products of c o r r o s i o n are l i k e l y t o r e a c h t h e s a t u r a t i o n c o n c e n t r a t i o n corresponding t o t h e minimum temperature of t h e system.

Continued op-

e r a t i o n would t h e n r e s u l t i n p r e c i p i t a t i o n on t h e steam g e n e r a t o r t u b e s ( t h e c o o l e s t s u r f a c e i n t h e i n t e r m e d i a t e system) w i t h r e s u l t a n t l o s s i n heat t r a n s f e r capability.

It i s proposed t o p r o t e c t v i t a l h e a t t r a n s f e r

s u r f a c e s from t h i s f o u l i n g by providing f o r p r e f e r e n t i a l d e p o s i t i o n of c o r r o s i o n products i n a c o l d t r a p whose temperature would be maintained

49 a s u i t a b l e amount below t h a t o f t h e h e a t exchanger.

This s e c t i o n d e s c r i b e s

some t e s t s t h a t were run t o develop i n f o r m a t i o n on t h e n a t u r e and k i n e t i c s of formation of c o l d s u r f a c e d e p o s i t s .

A c o l d f i n g e r was f a b r i c a t e d from a p i e c e of n i c k e l rod, 5/8 i n . OD by 1 1/2 i n . l o n g ( F i g . 15).

An a t t e m p t w a s made t o enhance t h e h e a t

t r a n s f e r p r o p e r t i e s by m i l l i n g a series of c i r c u m f e r e n t i a l grooves on t h e e x t e r i o r s u r f a c e and by forming t h e i n t e r i o r space i n f i v e o p e r a t i o n s w i t h

a 1 / 8 - i n . -diam d r i l l .

The o p e r a t i n g temperature w a s sensed by 0.040-in.

diam Inconel-sheathed thermocouples i n s e r t e d i n f o u r 0.055-in.-diam v e r t i -

c a l , e q u a l l y spaced h o l e s l o c a t e d s o t h a t t h e o u t e r edge of each h o l e w a s about 0.045 i n . away from t h e s u r f a c e of t h e t e s t p i e c e ( F i g . 3/8-in.-OD

16). A

n i c k e l t u b e w a s welded t o t h e t e s t p i e c e , and t h i s , i n combi-

n a t i o n w i t h a c e n t r a l 1 / 8 - i n . -OD t u b e , provided a r e e n t r a n t - t y p e a r r a n g e ment f o r i n t r o d u c t i o n and removal of t h e c o o l a n t , a mixture of argon and d i s t i l l e d water.

Other t u b e s and f i t t i @ s were provided s o t h a t t h e assem-

bled u n i t would be able t o s a t i s f y t h e containment and m o b i l i t y c r i t e r i a

(Fig.

1 7 ) . A c a t c h pan (small metal d i s k ) w a s a t t a c h e d t o t h e bottom of

t h e c o l d f i n g e r i n t h e hope t h a t it would r e t a i n p i e c e s which might become detached from t h e s u r f a c e of t h e t e s t p i e c e .

During a t e s t , t h e u n i t w a s

a t t a c h e d t o t h e s a l t sample a c c e s s nozzle on t h e pump bowl, t h e sample b a l l v a l v e w a s opened, and t h e i n n e r -Lube w a s i n s e r t e d u n t i l t h e lower half of t h e t e s t p i e c e w a s submerged under t h e s a l t s u r f a c e .

Movement of

t h e c o l d f i n g e r w a s through a Teflon seal above t h e b a l l v a l v e .

A f t e r the

t e s t p i e c e w a s i n p o s i t i o n , t h e c o o l a n t flow w a s s t a r t e d , and t h e t o t a l and r e l a t i v e flows of argon and d i s t i l l e d w a t e r were a d j u s t e d t o o b t a i n t h e d e s i r e d temperature.

A s a r e s u l t of e x p e r i e n c e d u r i n g shakedown t e s t s ,

two r e v i s i o n s were made:

(1)two of t h e f o u r thermocouples w e r e e l i m i n a t e d

because space l i m i t a t i o n s made o p e r a t i o n w i t h t h e l a r g e r number impossible, and ( 2 ) t h e c a t c h pan w a s e l i m i n a t e d because of c l e a r a n c e problems between

it and i n t e r n a l hardware i n t h e pump bowl. A t o t a l of f i v e t e s t s were r u n w i t h t h e c o l d f i n g e r t o i n v e s t i g a t e t h e e f f e c t of w a l l t e m p e r a t u r e on t h e amount and t y p e of d e p o s i t o b t a i n e d . Each t e s t p e r i o d was

6 hr.

I n a d d i t i o n , two tests were run with a 2 - h r

t e s t p e r i o d t o check t h e e f f e c t of t i m e . i n Tables 6 and

The t e s t results are summarized

Some d e p o s i t w a s o b t a i n e d i n a l l t h e 6-hr t e s t s ; none

ORNL Dlt 72-2001

0.378-m. DlAM X

hih DEEP 4 HOLES ON

OMO-n MAM

. .

NO. 54 1OOSSh.)

ON 04eo-in

o 30 to.izese1

ORILL l t i n DEEP. t HOLE

Fig. 15.

Cold-finger d e t a i l , fluoroborate c i r c u l a t i o n t e s t , PKF

loop.

Fig. 16.

Cold f i n g e r showing connecting tubing and thermocouples.

Fig. 17.

Cold-finger assembly.

53 w a s o b t a i n e d i n t h e 2-hr t e s t s .

A l l d e p o s i t s w e r e b r i g h t green, and t h e

amount v a r i e d from v e r y t h i n i s o l a t e d s p o t s t o a uniform c o a t i n g over t h e 1 1/2-in.2 surface.

No d a t a were o b t a i n e d on t h e weight o f material

deposited; however, t h e t o t a l amount of material i n t h e h e a v i e s t d e p o s i t

i s e s t i m a t e d t o have been <O.5

Chemical a n a l y s e s i n d i c a t e d t h a t as

t h e w a l l temperature of t h e c o l d f i n g e r w a s i n c r e a s e d , t h e q u a n t i t y o f chromium i n t h e t r a p p e d sample i n c r e a s e d r e l a t i v e t o t h e o t h e r c o n s t i t u ents.

A rough atomic balance can b e achieved i f one assumes t h a t t h e

d e p o s i t s c o n s i s t e d of a small amount of N+CrFE, mixed w i t h l a r g e amounts

of NaBF, and NaF. The d a t a from t h e c o l d - f i n g e r t e s t s are t o o meager t o permit any f i n a l conclusions.

The r e s u l t s , however, are s u f f i c i e n t l y promising t o

i n d i c a t e t h a t removal of c o r r o s i o n products by c o l d t r a p p i n g i s p o s s i b l e and t h a t f u r t h e r development e f f o r t i s j u s t i f i e d .

Table 6.

Summary of c o l d - f i n g e r t e s t s

S a l t c i r c u l a t i n g temperature, 1 0 2 5 " ~

Test No.

1 2

3 4 5 6 7

Date of test

Wall temperature ( OF)

750

4 -2 3-69 4-29-69 5-7-69 5-9-69 6-13-69 6-20-69 6-20-69

850 950

890 860 944 929

5.4

Test duration (hr)

Deposit

6 6 6 6 6

Yes

Yes, two s m a l l areas Yes, t h i n Y e s , heavy

O f f - G a s System Flow R e s t r i c t i o n s

A p r o f i l e o f t h e o f f - g a s l i n e i s shown i n F i g .

18. The l e n g t h and

l a y o u t of t h e l i n e were f o r t u i t o u s , and t h e p r o f i l e i s shown p r i m a r i l y t o i l l u s t r a t e t h e r a t h e r l e n g t h y and t o r t u o u s flow p a t h between t h e pump

54 bowl o u t l e t and t h e s u c t i o n l i n e of t h e v e n t i l a t i o n blower.

During most

of t h e l o o p o p e r a t i o n s t h e o f f - g a s flow w a s 1500 c$(STP)/min, pump bowl p r e s s u r e w a s 24 p s i g .

and t h e

The gas temperature a t t h e pump bowl

e x i t w a s c l o s e t o t h e s a l t temperature (normally lO25"F), b u t t h e gas quickly cooled t o room temperature i n t h e unheated o f f - g a s l i n e .

Down-

stream of t h e p r e s s u r e c o n t r o l v a l v e , t h e p r e s s u r e w a s e s s e n t i a l l y atmospheric. Table 7.

Test

No.

Analyses of d e p o s i t s from c o l d - f i n g e r t e s t s

Wall temperature

( OF) Weight

25.4

5.07

59.0

1.54

750 850

24.4

4.28

1.61

890

24.0

6.26

57.3 46.5

1.52

2.76 4.18 8.38

0.031 0.009

0.090

Atomic zbundance r e l a t i v e t o Fe

3c 3e

5.4.1

17 1.7 le

1-13

124

Plugging experience Continuicg d i f f i c u l t > - w a s experienced w i t h flow r e s t r i c t i o n s i n t h e

off-gas system.

The p r i n c i p a l t r o ? & l e s p o t s were (1) j u s t downstream of

t h e pump bowl, ( 2 ) t h e p r e s s u r e c o n t r o l v a l v e , and ( 3 ) t h e extreme end

of t h e o f f - g a s p i p e at t h e p o i n t where t h e o f f - g a s stream w a s vented i n t o t h e 1 2 - i 2 . s u c t i o n l i n e t o t h e v e n t i l a t i o n blower. The r e s t r i c t i o n s a t t h e pump bowl o u t l e t were due t o s a l t m i s t t h a t

w a s g e n e r a t e d i n t h e pump bowl and c a r r i e d out by t h e o f f - g a s .

When t h e

gas stream cooled below t h e f r e e z i n g p o i n t of t h e s a l t (725"F), t h e m i s t p a r t i c l e s f r o z e and some f r a c t i o n of them agglomerated and s e t t l e d out on t h e pipe w a l l .

Eventually t h e flow became blocked.

ORNL-DWG 7 2 - 2 0 8 2

* INDICATES

90' CHANGE I N HORIZONTAL DIRECTION. TOTAL LENGTH OF OFF-GAS LINE FROM PUMP BOWL TO BLOWER SUCTION L I N E = 67 f t

@ PUMP BOWL OFF-GAS OUTLET @ YORK MESH FILTER @ 50-p METALLIC FILTER @ PUMP BOWL PRESSURE CONTROL VALVE 3/8-~n

@ @ @

SUCK-BACK TRAP MINERAL OIL BUBBLER FORWARD BLOW TRAP

OD __

TUBING

0 0

> 0

0 5 z c

W 1 W

0 I

F i g . 18.

20 25 30 35 HORIZONTAL DEVELOPED LENGTH ( f t )

P r o f i l e o f f l u o r o b o r a t e (PKF) l o o p off-gas l i n e .

R e s t r i c t i o n s at t h e c o n t r o l v a l v e w e r e a s c r i b e d t o two t h i n g s :

(1)

t h o s e m i s t p a r t i c l e s t h a t d i d n o t s e t t l e out i n t h e p i p e were c a r r i e d downstream and d e p o s i t e d i n t h e v a l v e 13:;

i n e r t i a l f o r c e and ( 2 ) a v i s -

cous f l u i d w a s c a r r i e d out of t h e pump bowl by t h e o f f - g a s stream and condensed out i n t h e c o n t r o l v a l v e and o t h e r p l a c e s i n t h e o f f - g a s l i n e s . During t h e i n i t i a l o p e r a t i o n of t h e l o o p w i t h t h e f l u s h i n g s a l t , t h e emission rate of t h e f l u i d w a s v e r y high, and an e s t i m a t e d 50 d r a i n e d from t h e l i n e downstream of t h e c o n t r o l v a l v e .

CI#

was

With continued

o p e r a t i o n , however, t h e r a t e dropped o f f c o n s i d e r a b l y and l e v e l e d o f f

a t about 6 t 3 mg/hr ( e q u i v a l e n t t o about 1 g p e r 15,000 l i t e r s of gas o r 0.07 m g / l i t e r )

The r e s t r i c t i o n s t h a t occurred a t t h e extreme end of t h e o f f - g a s l i n e were attrib3:ted

t o a slow b u i l d u p of materials r e s u l t i n g from a re-

a c t i o n between BF, and w a t e r .

The E3F3 w a s normally p r e s e n t i n t h e off-

gas stream a t akout 3 . 7 $ V;; volume, and t h e w a t e r c o n t e n t o?' t h e b u i l d i n g atnosphere w a s proba'cly alocit 1% ly volume. arout 2 t o

4 in.

The p l u g s normally occurred

from t h e end of t h e 3 / 8 - i n . l i n e ( F i g .

19). We assume

t n a t t l e m o i s t u e d i f f u s e d up t:-e s m a l l l i n e t o t h i s p o i n t , where it comt i z e d w i t h t h e 2F3 coming downstream and t n e r e a c t i o n product w a s gradu-

a l l y deposited.

A t o t a l of s i x plugs were formed.

The t i m e of formation

( s a l t c i r c u l a t i o n t i m e ? w a s not c o c s i s t e n t , varying f'rom s i x weeks t o s i x x o c t h s , as shown i c T a t l e 1. Tze identit:; of t h e plug material i s su'cject t o s p e c u l a t i o n s i n c e cnemical ar,al.,-ses were not made.

The p r i n c i p a l r e a c t i o n product* f'rom

conbination of' EF, and water i s thought t o ?.e EF, .2K,O,

which presumably

would not be a s o l i d a t t h e c o n d i t i o n s (atmospheric p r e s s u r e and room t e m p e r a t u r e ) under which t h e plugs were formed.

5.4.2

Off-gas t e s t s

I n December lgC8, t h e o f f - g a s l i n e a t t h e pump bowl o u t l e t w a s modif i e d t o provide f o r t h e i n s t a l l a t i o n of experimental equipment t o e v a l u a t e

methods of coping w i t h s a l t m i s t and o t h e r contaminants i n t h e o f f - g a s

*Private communications, R . F. Apple t o A. N . Smith, Nov. 22,

< I

1971.

Fig. 19. Radiograph of t y p i c a l plug (formed 9-11-68) t h a t formed at extreme end of off-gas line. Nal3F1, circulation t e s t , PKF loop.

stream.

The following i s a d e s c r i p t i o n o f t h e t e s t s t h a t were performed

from December April

1970.

19, 1568, u n t i l t h e f i n a l shutdown

o r the facility in

During t h e d i s c u s s i o n , r e f e r e n c e may b e made t o F i g s . 20 t o

23 f o r design d e t a i l s and o t h e r p e r t i n e n t information r e l a t i v e t o t h e o f f - g a s l i n e and t h e v a r i o u s t r a p s and f i l t e r s used during t h e t e s t s ; t o F i g s . 24 t o 2c1 f o r t h e p a r t i c u l a r o r d e r i n which t h e v a r i o u s components were arrayed; and t o Table 9 f o r a c h r o n o l o g i c a l summary and f o r data on c o l l e c t i o n rates f o r s a l t m i s t s and condensed l i q u i d .

Connections be-

tween components were made w i t h 3/8-in. -OD ( 5 / 1 6 - i n . - I D ) t u b i n g , t u r n s

were made u s i n g long r a d i u s bends, and t h e t o t a l l e n g t h of i n t e r c o n n e c t i n g t u b i n g between t h e pump bowl nozzle and t h e f i n a l component i n t h e t e s t s e c t i o n w a s never more t h a n

Table

2%.

Record of flow r e s t r i c t i o n s

a t e x t r e n e end of o-t'f-gas l i n e ~

Salt circulation tine (hr)

Tot a1 elapsed time (hr)

9-11-e ?> 12-16- i l

1350

3200

1270

2 300

1-29 -69

1060

8-22-;9

980 41; 0

11-25-69

1720

2230

2-18-79

1100

2000

Date ok,served

4870

For t h e i n i t i a l s e r i e s of t e s t s , a Calrod h e a t e r w a s i n s t a l l e d on t h e o f f - g a s l i n e a t t h e p o i n t of connection w i t h t h e pump bowl ( F i g . 2 0 ) . The arrangelnent w a s such t h a t , with no power t o t h e h e a t e r , and w i t h t h e system o p e r a t i n g a t normal s t e a w - s t a t e c o n d i t i o n ( b u l k s a l t temperature of 1025째F and o f f - g a s flow of 1 . 5 l i t e r s / m i n ) , t h e temperature of t h e 1 / 2 - i n . - I D off-gas l i n e dropped f'rom 755째F a t t h e pump bowl t o 400째F at a p o i n t 3 1/2 i n . away from t h e pump bowl, and it i s estimated t h a t t h e

ORNL-DWG 72-2083

2 % - i n . D l A M X 3 - i n . HIGH EXIT PLENUM T Y P I C A L T E M P E RATU R E P R O F I L E WITH CALRDD HEATER TURNED OFF D E T A I L OF P U M P B O W L O F F - G A S N O Z Z L E - T E S T S

-FIVE

-I

-i--

IoTO

E A C H 0 . 0 2 0 - i n . P L A T E S W I T H FOUR E A C H 3/32- X 3/32- in. N O T C H E S

FOUR EACH 0 . 0 2 0 - i n . P L A T E S W I T H FOUR E A C H % - i n . D I A M H O L E S H O L E C E N T E R S T O B E 9/32in. F R O M P L A T E CENTER

?-OUT

BAFFLE PLATE DETAIL-TEST 110 ONLY IN V E R T I C A L H O T - M I S T T R A P D E T A I L - T E S T S I I a T O IIc

L 0

in.+

OUT

12 in.

-I$

2-in.PIPE I

NOTES I . COLD E L E M E N T NOT USED I N A L L TESTS. 2. E L E M E N T D l A M - 1.8 in. 3. E L E M E N T A R E A - O . 0 ( 8 f t 2 4. FLOW R A T E - 3 scfrn/ft2 AT 1.5 liters/rnin ( S T P )

I I

( F R O Z E N SALT FILTER (COLD E L E M E N T ) EN SALT DEMISTER (HOT E L E M E N T ) HEATER AND I N S U L A T I O N H O R I Z O N T A L HOT-MIST

TRAP DETAIL-TESTS

I I I a TO I I I d

F i g . 20. Details o f off-gas n o z z l e and hot-mist t r a p s f o r NaBF4 c i r c u l a t i n g t e s t , PKP l o o p .

O R N L- D W G 7 2 - 2 0 8 4

ID TUBING

L I N E A R V E L O C I T Y O F G A S AT -1.5 l i t e r s / r n i n ( S T P ) AND 2 4 p s i g WAS 0.018 f p s A N D RESIDENCE T I M E WAS i l O s e c

GLASS P I P E 3 1 n ID BY 2 4 - i n . LONG--,

ASSUMING SPHERICAL ? A R T I C L E S O F s p g r = 2.0, A SETTLiNG R A T E O F 0.018 f p s I N H E L I U M CORRESPONDS TO A PARTICLE SIZE OF 9 p . THEREFORE, PARTICLES 2 fop SHOULD REMAIN IN T H E S E T T L I N G TANK

' I __ D E T A I L O F S E T T L I N G TANK ( S T )

1 UNIT 1

IMPACT ,/' S E R F A C E \\>

u .

1-1

I-2

i N SERVICE

I1-13-69

I '-22-69

TO 1 - 2 2 - 6 9 TO 2- 9-69

L;,i

"L"

6 in.

42 in.

I 3/8 in.

D E T A I L O F IMPACTOR U N I T S - T E S T

1 I I "9"

F i g . 21. S e t t l i n g t z n k and i n p a c t o r u n i t s , t e s t s I a and I b , PJaBFb c i r c u l a t i o r i t e s t , PK? loop.

72-2085

ELEMENT MODEL

F-fa F--fb F-fc

FM204 NEVACLOG

FM225

Flin204

FM225

FM204

N O T E : A L L E L E M E N T S WERE S T A I N L E S S S T E E L

-1 X 3 i n . GLASS P I P E L , " REDUCERS

ORNL-DWG

F I L T E R DIAM--1.75 AREAO.Ot7 f t '

in FLOW

= 3.f scfrn/ft'

AT 1.5 l i t e r s ( S T P ) / m i n

NOTES 1 . F I L T E R E L E M E N T S T Y P E F M A R E M A D E BY H U Y C K M E T A L S , I N C M F R ' S REMOVAL RATINGS WYEN FILTERING G A S E S . F M - 2 2 5 9 8 % L E S S T H A N f . 4 ~ (OO%LESS TWAN 5 p F M - 2 0 4 100% L E S S T H A N 0 1 p 2 NEVA-CLOG FILTER M A T E R I A L I S BY M U L T I - M E T A L WIRE CLOTH, I N C , AND CONSISTS O F T W O P E R F O R A T E D S H E E T S F A S T E N E D T O G E T H E R W I T H A E O U T A 1/64 n S P A C I N G B E T W E E N T H E M , A N 0 A R R A N G E D SO T H A T T H E P E R F O R A T O N S l'u O N E S H E E T ARE NOT I N L I V E WITH THOSE OF T H E O T H E R . T H E PERFORATIONS A R E 0 0 4 4 in. D l A M O N 0 -13 in. C E N T E R S , E Q U I V A L E N T TO 10% O P E N A R E A F I L T E R T Y P E F-4

F LT ,IE ,R

E L E M E N T TYPE G

B y P A L L T R I N I T Y MICRO CORP., GLASS P I P E 3 in. I D BY 8 in. L O N G

SINTERED STAINLESS STEEL, 2 . 7 5 in. D l A M X 6 In. LONG, F I L T E R A R E A - 0 . 3 6 ft', MFR'S REMOVAL ~% f . 8 , ~ R A T I N G 9 8 % 0 . 7 f~O O F L O W = 0.15 s c f m / f t 2 A T 1.5 l i t e r s ( S T P ) / r n i n

FILTER T Y P E

F i g . 22.

PKP loop.

F-2

FILTER E L E M E N T T Y P E 2232 Bv HOKE, INC., S I N T E R E D STAINLESS STEEL, FILTER AREA 0 0 0 6 f t ' MFR'S RATING 5 - 9 p

FLOW = 8.8 s c f m / f t ' AT j.5 l i l e r s ( S T P ) / r n i n

FILTER TYPE F-3

F i l t e r s used during off-gas t e s t s i n NaBF4 c i r c u l a t i o n t e s t ,

ORNL-DWG

72-2086

3/8-in. OD TUBING

-7 I1

E-

LINEAR VELOCITY OF GAS AT 1.5 liters/min ( S T P ) AND 2 4 p s i g WAS 0.076 f p s AND RESIDENCE TIME IN 1 1 in. COLD SECTION WAS 12 sec

GLASS P I P E 1 in. ID BY 18in. LONG-

4. ,WET-ICE

BATH

11 in.

2 in.

WET-ICE COLD TRAP ( C T - W I )

I 2 in. i

1 J

-3 in.*

'/z-in.-OD

LINEAR VELOCITY OF GAS AT 1.5 liters/min ( S T P ) AND 2 4 p s i g WAS 0.75 f p s AND RESIDENCE T I M E WAS 2.5 sec

SS TUBING

DRY - I C E - T R I C H LO R0 ET HYCE N E BATH

D R Y - I C E COLD TRAP ( C T - D I )

F i g . 23. Cold t r a p s u s e d d u r i n g off-gas system t e s t s , NaBF4 c i r c u l a t i o n t e s t , PKP loop.

ORNL-DWG

72-2087

I -

TEST I o 12-19-68

TO 1-13-69

W E T - I C E COLD T R A P (CT-WI)

SETTLING TANK ( S T ) /

I-

[HEATER

FILTER (F-1 b)

IMPACTOR (1-1, 1 - 2 )

T E S T Lb (-(3-69

IMPACTOR 1-1 TO ( - 2 2 - 6 9

TEST I b

IMPACTOR 1-2 TO 2 - 9 - 6 9

(-22-69

I FILTER (F-ib)

T E S T IC 2 - 9 - 6 9 TO 3 - 7 - 6 9

F i g . 24. Arrangement o f off-gas t e s t equipment, t e s t s I a t o NaBF4 c i r c u l a t i o n t e s t , PKF l o o p .

64 ORNL-DWG

HMT-VI

-Th

72-2088

TEST E O 3-25-69

TO 5 - 4 3 - 6 9

NOTE: H M T - V I WAS E Q U I P P E D WITH DISK AND DONUT BAFFLE ARRANGEMENT

P U M P BOWL -ICE COLD T R A P (CT - W 1)

F-

TEST I I b

HMT-V2

5-26-69 NOTE

TO 6 - 2 6 - 6 9

ti k i T - V 2 W A S E Q U I P P E D W I T H 14.39 W I R E M E S H (YORK M E S H ) COMPACTED I N 2 L I N E A R in. G I V I N G A VOID FRACTION

93%

-ICE COLD TRAP (CT-WI)

6-26-69

TO 1 0 - 3 0 - 6 9

PUMP BOWL WET-ICE

COLD T R A P

F i g . 2 5 . Arrangement of off-gas t e s t equipment, t e s t s I I a t o I I c , NaBF4 c i r c u l a t i o n t e s t , PKP l o o p .

O R N L - DWG 7 2 - 2 0 8 9

I ABOVE SALT MELTING POINT

! BELOW SALT

I. I

MELTING POINT

3OOOF

\HOT-MIST TRAP HORIZONTAL MODEL WET-ICE COLD TRAP (CT-WI)

\ TEST

PUMP B O W L

TIME PERIOD

HOT M I S T TRAP

HOT ELEMENT

COLD ELEMENT

1110

11-7-69

TO I f - 2 4 - 6 9

HMT-Hf

FM-225

lIIb

12-5-69

TO 12-23-69

HMT-H2

NEVACLOG

NONE USED

IIIc

4-20-70

TO 3

- 4 -70

HMT-H3

FM-225

LIIe

3-24-70

TO 4 - 1 3 - 7 0

HMT-H3

FM-225

. NONE USED

Fig. 26. Arrangement of off-gas t e s t equipment, t e s t s IIIa t o I I I c , NaBFt, c i r c u l a t i o n t e s t , PKP loop.

Chronological summary of tests and data collection r a t e s for salt mists and condensed l i q u i d

!Cable 9.

Collection data

late

Test

Cumulative circulating time (b)

12-19-68

1-13-69

622

1 1 3 bg

1-15-69

Component

Total time on stream (b)

Total weight collected (9)

Average

rate (gb)

Test f a c i l i t y s t a r t e d up after mdipying off-gas l i n e t o investigate off-gas emissions; c o l l e c t i o n equipment i n cludes settling tang (ST), wet i c e cold t r a p ( ~ - w I ) , and filter (Fl-a)

- -

Remarks

S e t t l i n g tank, wet I c e cold t r a p , and f i l t e r removed Prom system lmpactor u m t {' 1 - i r a n d r i i t e r (ri-oj

670

ST CT-WI Fl-8

622 622 622

6: 8

1-1 Fl-b

210 210

97 14

1-2

430

Fl-b

- 0.10 0.007

s L

0.013

0.46

0.07

s s

0.012

1070

0.004

Pressure drop at pmp bowl o u t l e t I s 6.5 psi; r e s t r i c t i o n cleared by increasing temperature of off-gas l i n e at pump bowl o u t l e t

1-224 1-22-69

830

1-30-69

lox)

Impactor unit, 1-1 removed Impactor u n i t 1-2 I n s t a l l e d

Pressure drop a t pump bowl o u t l e t is 4.5 psi; r e s t r i c t i o n cleared by increasing temperature of off-gas l i n e at pump bovl o u t l e t

2-9-69

1250

Impactor unit 1-2 removed because of r e s t r i c t i o n i n inlet line

3-6-69

1870

Pressure drop a t pump bowl o u t l e t is 8.0 psi; r e s t r i c t i o n

3-7-69

1900

cleared by heating off-gas line Test f a c i l i t y shut down t o i n s t a l l hubmist t r a p Test f a c i l i t y s t a r t e d up after i n s t a l l a t i o n of v e r t i c a l hot-mist t r a p s v i t h I n t e r n a l disk-donut b a f f l e s (HMP-Vl); c o l l e c t i o n e q u i p n t includes s i n t e r e d metal f i l t e r F-2, absolute filter Fl-c, and wet i c e cold t r a p CT-WI

3-25-69

- --.

4-21-69

650

Removed f l l t e r Fl-c

Fl-C

650

0.02

0.0003

5-2-69

900

Replaced sintered metal filter F-2 v i t h s i n t e r e d metal a l t e r F-3; r e i n s t a l l e d f i l t e r Fl-c

F-2

900

0.008

Test f a c i l i t y shut down t o change hot-mist t r a p

m-v1

1145

9 5.1 0

0.008 0.02 0

s s s

5-13-69

ll45

F- 3

Fl-C

6-26-69

1910

6-26 -69

TIC

10-30-69

11-24-69

4610

12-23-69

410

3-4-70

840

Test f a c i l i t y shut dovn t o change hot-mist t r a p

F-3 CT-WI

765

15.1 6.4

0.02 0.009

740

50 12

0.02 0.005

0.013

Test f a c i l i t y shut down t o i n s t a l l horizontal hot-mist trap

Fl-C

q-w1

2700 2700

Test f a c i l i t y shut down t o change hot-mist t r a p

IBlT-81 F- 3 CT-WI

410 320

410

2.5

0.008

s s

3.3

0.008

5.3

cn cn

Test f a c i l i t y shut dam t o change hot-mist t r a p

HMT-H2 F-3 CT-WI

430 430 430

HMP-H3 F-3 m-WI

lo00 1000 lo00

m-WI m-DI

1.8 1.8

0.004

S S

2.5

0.006

0.004

Test f a c i l i t y s t a r t e d up Vith t h i r d horizontal hot-mist t r a p (HMC-H3); sane collection equipnent

1840

Test f a c i l i t y shut d a m t o change hot-mist t r a p and prepare f o r water inJection test

0.03

0.4 5.6

O.OOO4 0.006

s L

215 200

1.8

0.008

0.24

0.012

L L

m-WI

265

2.7

0.01

CT-DI

265

0.85

0.003

Test f a c i l i t y s t a r t e d up t o run water i n j e c t i o n test; hot-mist t r a p I s same as in test I I I c ; collection equipment includes wet I c e cold t r a p m-WI and dry i c e cold t r a p CT-DI

3-24-70

4-2-70

0.006

Test f a c i l i t y st&ed up with second horizontal hot-mist t r a p (m-m); same collection e q u i p n t

1-20-70

IIIC

Test f a c i l i t y s t a r t e d up v i t h first horizontal hot-mist t r a p (W-Hl);collection equipment includes sintered m e t a l f i l t e r F-3 and w e t i c e cold t r a p CT-WI

12-5-69

IIIb

1145

Test f a c i l i t y s t a r t e d up with v e r t i c a l hot-mist t r a p with single h a f f l e p l a t e at inlet; collection equipment includes f i l t e r Fl-c and wet i c e cold t r a p a-WI

11-7-69

IIIa

CT-WI Test f a c i l i t y s t a r t e d up with v e r t i c a l hot-mist t r a p with wire screen demister (HMP-V2); c o l l e c t i o n equipment includes sintered metal f i l t e r F-3 and wet i c e cold t r a p m-WI

5-26-69

IIb

245 2C5

2055

Check t r a p weights

4-2-70

2056

Injected 10 g %O

4-13-70

2320

Test f a c i l i t y shut dovn

= salt; L = l i q u i d .

i b t o loop

67 W

l i n e w a s a t t h e salt m e l t i n g p o i n t (725째F) a t about from t h e pump bowl.

1/4 t o

1 / 2 i n . away

BJ applying power t o t h e h e a t e r , t h e temperature

p r o f i l e could be s h i f t e d s o t h a t t h e temperature of t h e l i n e d i d n o t drop below t h e s a l t m e l t i n g p o i n t u n t i l a p o i n t pump bowl.

4 i n . or

more away from t h e

A t 5 1 / 2 i n . from t h e pump bowl, a n a d a p t e r w a s i n s t a l l e d

t h a t converted t h e o f f - g a s l i n e from 1/2- t o 5/16-in.-ID t u b e .

About

30 i n . downstream of t h e a d a p t e r , t r a p s and f i l t e r s were i n s t a l l e d t o s e p a r a t e and c o l l e c t t h e materials t h a t were e m i t t e d with t h e o f f - g a s

stream. The f a c i l i t y w a s o p e r a t e d with t h e above arrangement f o r 1900 hr (Table 9 ) .

The procedure w a s t o o p e r a t e without power t o t h e o f f - g a s

l i n e h e a t e r u n t i l e x c e s s i v e p r e s s u r e drop a t t h e pump bowl o u t l e t i n d i c a t e d t h e formation of a s a l t p l u g .

The h e a t e r w a s t h e n t u r n e d on and

t h e temperature of t h e l i n e i n c r e a s e d u n t i l a s h a r p d e c r e a s e i n p r e s s u r e drop i n d i c a t e d t h a t t h e plug had melted.

Using t h i s method, r e s t r i c t i o n s

a t t h e pump bowl o u t l e t were c l e a r e d after 670, 1020, and 1870 h r of c i r culation (Fig. 27).

A t t h e s t a r t of t h e t e s t s , t h e c o l l e c t i o n equipment

c o n s i s t e d of a 3-in.-ID g l a s s s e t t l i n g t a n k (ST), a 1 - i n , - d i a m wet,-ice c o l d t r a p (CT-WI),

and a porous metal f i l t e r ( F l - a ) .

After 622 h r t h e

s e t t l i n g t a n k and c o l d t r a p were removed, and d u r i n g t h e next 630 hr two d i f f e r e n t models of impactor u n i t s were t e s t e d .

A f t e r 1250 hr t h e

second impactor u n i t w a s removed, and t h e f i n a l 650 h r of o p e r a t i o n

( t e s t I C )were completed w i t n only t h e porous metal f i l t e r ( F l - b ) i n t h e line.

Table

period.

9 summarizes s o l i d and l i q u i d c o l l e c t i o n rates for t h i s t e s t

A f t e r completion of t e s t IC, a s a l t plug w a s found

ir,

t h e inlet

t o t h e porous metal f i l t e r ( F i g . 2 8 ) . Following completion of t h e f i r s t group of L,ests, it

W ~ Sconcluded

t h a t t h e bes5 approach t o t h e s a l t m i s t problem w a s t o use a hot-mist t r a p , t h a t i s , one t h a t i s o p e r a t e d a t a temperature above t h e s a l t m e l t i n g point,, t o c o l l e c t a l a r g e f r a c t i o n of t h e s a l t m i s t and r e t u r r ,

it c o n t i n u o u s l y t o t h e s a l t system or s t o r e it u n t i l s u i t a b l e d i s p o s i t i o n could b e made.

The s a l t overflow, t h a t i s , t h e f r a c t i o n not s e p a r a t e d

out by t h e h o t - m i s t t r a p , would be cooled below t h e s a l t ' m e l t f n g p o i n t W

and t h e f r o z e n s a l t p a r t i c l e s removed by a r e p l a c e a b l e f i l t e r .

The ob-

j e c t i v e of t h e second s e r i e s of t e s t s w a s t o o b t a i n performance dzca on hot-mist t r a p s u s i n g d i f f e r e n t i n t e r n a l arrangements f o r i n t e r c e p t i o n

68 V

I I ~

-' \ 1 7 ,

HEAT APPLIED TO RELIEVE RESTRICTION

y i '

c I

P-

/ L

Fig. 27. P r e s s u r e drop a c r o s s pump bowl off-gas outlet n o z z l e , variation w i t h t i m e .

Fig. 28. 7

Salt plug fo

1969. NaBF4 circulation t

n 5 1/16-in. line at filter i n l e t , Mar. 7,

of t h e s a l t m i s t .

The t r a p housing c o n s i s t e d of a 1-in.-ID p i p e , 1 3 i n .

long ( F i g . 2 0 ) , v e r t i c a l l y o r i e n t e d .

The lower p a r t of t h e t r a p and t h e

o f f - g a s l i n e between t h e pump bowl and t h e t r a p w e r e h e a t e d and i n s u l a t e d ,

s o t h e off-gas temperature w a s h e l d above t h e s a l t m e l t i n g p o i n t u n t i l t h e gas had reached t h e upper p a r t of t h e t r a p .

I n i t i a l l y (test IIa),

t h e hot-mist t r a p w a s equipped w i t h b a f f l e p l a t e s d r i l l e d a l t e r n a t e l y a t t h e c e n t e r and p e r i p h e r y t o c r e a t e continuously r e v e r s i n g c r o s s flow between p l a t e s .

A t o t a l of n i n e p l a t e s w a s used, w i t h 1 / 4 - i n . spacing

between p l a t e s . For t e s t IIb, t h e b a f f l e s were removed, and a 2 - i n . - l o n g bundle of

w i r e mesh (York mesh) weighing 14.3 g w a s i n s t a l l e d .

For t h e f i n a l t e s t

( t e s t I I c ] , t h e wire mesh w a s removed and t h e hot-mist t r a p w a s o p e r a t e d without any i n t e r n a l hardware except â&#x201A;Źor a 3 / 4 - i n . -diam d e f l e c t o r p l a t e

a t t h e i n l e t end.

Three d i f f e r e n t t y p e s of porous metal f i l t e r w e r e used

f o r s o l i d s c o l l e c t i o n during t h e series I1 t e s t s .

Operating data f o r

t e s t s IIa, I B , and I I c are p r e s e n t e d i n Ta5le 9 .

The t e s t s were s t a r t e d

on March 25,

1968, and

t i m e w a s 4600 h r .

completed on October 30,

1969; t o t a l

circulating

T e s t I I c w a s i n t e r r u p t e d t w i c e because of s a l t plugs

at t h e hot-mist t r a p o u t l e t and once j e c a u s e of a s a l t plug at t h e i n l e t t o t h e porous metal f i l t e r . I n t h e f i n a l series of t e s t s ( I I I a t o I I I d ) , i n v e s t i g a t i o n of t h e hot-mist t r a p i d e a w a s continued, b u t changes were made i n t h e geometry, The s i z e of t h e t r a p w a s i n c r e a s e d

o r i e n t a t i o n , and demister material.

t o 2 i n . dim by 18 i n . long, and it w a s t u r n e d so t h a t t h e l o n g axis w a s horizontal (Fig. 20).

I n t h e f i r s t t e s t ( I I I a ) , t h e demister mate-

r i a l w a s porous metal t y p e FM-225 (Huyck Metals, I n c . ), w h i l e i n t h e second t e s t (11%) it was a p e r f o r a t e d metal s h e e t material c a l l e d NEVACLOG (Multi-Metal Wire Cloth, Inc . )

For t h e t h i r d t e s t ( I I I c ) , t h e

FM-225 material w a s a g a i n used, and a second p i e c e of FM-225 w a s i n s t a l l e d i n t h e c o l d end of t h e m i s t t r a p t o c a t c h t h e f r o z e n s a l t p a r t i c l e s . D e s c r i p t i v e data f o r t h e v a r i o u s demister materials are g i v e n i n F i g . 22. I n a l l c a s e s , a porous metal f i l t e r (F-3) w a s used for s o l i d s c o l l e c t i o n

a t t h e o u t l e t of t h e hot-mist t r a p .

A f t e r b o t h t e s t s I I I a and IIn, each

of which l a s t e d about 400 h r , t h e o u t l e t l i n e from t h e hot-mist t r a p w a s V

found t o be blocked w i t h a b l a c k material, although only IIIl showed a s i g n i f i c a n t i n c r e a s e i n p r e s s u r e drop a c r o s s t h e h o t - m i s t t r a p ( 2 . 3 p s i

as compared w i t h a c l e a n AP of 0.4 p s i ) .

The b l a c k d e p o s i t w a s n o t

found after t e s t I I I c , and no a p p r e c i a b l e r i s e i n AP w a s noted during t h e 1000 h r of o p e r a t i o n .

f i n a l test ( I I I d ) was a special test t o

determine t h e e f f e c t s of i n j e c t i n g water d i r e c t l y i n t o t h e s a l t i n t h e pump bowl.

The hot-mist t r a p w a s t h e same design as t h a t used f o r t e s t

IIIC.

For b o t h t h e series I1 and I11 t e s t s , t h e c o l l e c t i o n equipment w a s e s s e n t i a l l y t h e same, t h a t i s , a h i g h - e f f i c i e n c y porous m e t a l f i l t e r followed by a w e t - i c e c o l d t r a p .

The t y p e of porous metal f i l t e r w a s

v a r i e d i n some c a s e s (see F i g s . 25 and 26 and Table

g),

and i n t h e f i n a l

t e s t ( I I I d ) , t h e porous metal f i l t e r w a s not used and t h e wet-ice c o l d t r a p w a s followed by a d r y - i c e - t r i c h l o r o e t h y l e n e

trap.

Operating and

c o l l e c t i o n d a t a f o r t h e series 111 t e s t s are shown i n Table

5.4.3

Discussion and e v a l u a t i o n of t e s t results The o f f - g a s system t e s t s are s u b j e c t t o t h e v a l i d c r i t i c i s m t h a t

t h e y w e r e t o o broad and shallow.

That i s , a l i m i t e d amount of experience

w a s o b t a i n e d over an e x c e s s i v e v a r i e t y of t e s t c o n d i t i o n s .

This l a c k of

in-depth s t u d y argues f o r t h e use of c a u t i o n i n r e a c h i n g conclusions based on t h e t e s t r e s u l t s .

With t h i s i n mind, we propose t o examine t h e t e s t

d a t a first on a q u a l i t a t i v e basis and t h e n t o d r a w whatever q u a n t i t a t i v e conclusions seem p e r m i s s i b l e . Tests Ia t o ICv e r i f i e d t h e f a c t t h a t t h e plugs o r flow r e s t r i c t i o n s t e n d t o form a t t h e f i r s t p l a c e i n t h e l i n e where t h e temperature f a l l s below t h e m e l t i n g p o i n t of t h e s a l t .

The t e s t s a l s o showed t h a t t h e

r e s t r i c t i o n s could be c l e a r e d by r a i s i n g t h e temperature of t h e l i n e . Although we d i d not have a measure of t h e s a l t temperature a t t h e e x a c t p o i n t s where t h e p l u g s had formed, we noted t h a t t h e l i n e temperature d i d n o t exceed 1100째F d u r i n g any of t h e times when h e a t w a s a p p l i e d t o clear a restriction.

W e conclude from t h i s t h a t t h e plugs were probably

NaBF4-NaF e u t e c t i c , o r some o t h e r mixture of NaBF4 and NaF, r a t h e r

t h a n oxide, which would t e n d t o have a m e l t i n g p o i n t c o n s i d e r a b l y h i g h e r t h a n 1100째F.

W e noted a l s o t h a t o t h e r t e s t s ( s e e S e c t . 5 . 2 . 2 ) implied

t h a t t h e o f f - g a s stream tended t o be i n e q u i l i b r i u m w i t h t h e b u l k c i r c u l a t i n g s a l t , and, s i n c e t h e o f f - g a s would be i n continuous c o n t a c t w i t h d e p o s i t s i n t h e off-gas l i n e , d e p o s i t e d mixtures o f NaBF4 and NaF would t e n d t o approach t h e b u l k s a l t i n composition.

F i n a l l y , we noted t h a t

chemical a n a l y s e s of s o l i d s d e p o s i t e d i n t h e o f f - g a s l i n e (sample PK-20,

11-4-68) corresponded c l o s e l y t o t h e NaBF4 -NaF e u t e c t i c composition. T e s t s I I a t o I I c and IIIa t o I I I c proved t h a t r e s t r i c t i o n s could be e l i m i n a t e d i f t h e l i n e were maintained a t a temperature above t h e

s a l t melting p o i n t and i f t h e l i n e were p i t c h e d s o as t o prevent t r a p p i n g of t h e molten s a l t i n low s p o t s , as evidenced by t h e f a c t t h a t no flow r e s t r i c t i o n s were experienced i n t h e h e a t e d l i n e between t h e pump bowl and t h e hot-mist t r a p s .

The occurrence of s a l t plugs a t t h e hot-mist

t r a p o u t l e t d u r i n g t e s t IIa i n d i c a t e d t h a t t h e s i m p l e s e t t l i n g tank w a s

not as e f f e c t i v e i n removing s a l t m i s t as t h e b a f f l e s or t h e w i r e mesh.

Tests I I I a t o I I I c seemed t o i n d i c a t e t h a t e i t h e r Huyck F e l t Metal

or blulti-Metal PSEVA-CLOC- could be used as an e f f e c t i v e demisting a g e n t . This conclusion i s based

or^

t h e l a c k of s i g n i f i c a n t s o l i d s accumulations

i n t h e porous metal f i l t e r ( F - 3 ) downstream of t h e h o t - m i s t t r a p s and, i n t h e c a s e of t e s t I I I c , on t h e f i l t e r element i n t h e cool end of t h e hot-mist t r a p .

We noted, however, t h a t t h e 5/16-in.-ID l i n e a t t h e o u t -

l e t of t h e hot-mist t r a p (upstream of f i l t e r F-3) w a s plugged w i t h a d a r k - s o l i d m a t e r i a l a f t e r b o t h t e s t s I I I a and 11I-b.

No plug of d a r k

m a t e r i a l w a s found a f t e r t e s t I I I c , which had a Huyck F e l t Metal c o l d elernect i n t h e c o o l zone of t h e hot-mist t r a p .

A l s o t e s t I I I c w a s op-

e r a t e d more t h a n t w i c e as long as I I I a and IIIb without an a p p r e c i a b l e i n c r e a s e i n p r e s s u r e drop over t h e "clean" v a l u e .

Thus t h e c l e a n CIP a t

s t a r t u p was 0 . 5 p s i , while t h e AP a f t e r 1000 h r w a s 0.75 p s i .

The source

of t h e b l a c k d e p o s i t s i s not known, b u t t h e y p o s s i b l y could have been due t o decomposition p r o d u c t s of l u b r i c a t i n g o i l t h a t i n a d v e r t e n t l y l e a k e d i n t o t h e pump bowl; we have no p o s i t i v e evidence, however, t h a t such an o i l l e a k o c c u r r e d .

Ir,o r d e r t o make i n t e l l i g e n t use of t h e q u a n t i t a t i v e d a t a from t h e off-gas system t e s t s , it i s necessary t o g i v e due c o n s i d e r a t i o n t o t h e

73 W

shortcomings t h a t were p r e s e n t i n t h e experimental d e s i g n .

First, the

procedure d i d n o t provide f o r p e r i o d i c checks t o i n s u r e t h a t t h e mass flow rate and p h y s i c a l p r o p e r t i e s of t h e s a l t m i s t i n t h e o f f - g a s stream

a t t h e pump bowl o u t l e t d i d not v a r y s i g n i f i c a n t l y with t i m e .

Also, it

seems l o g i c a l t o assume t h a t t h e flow of s a l t m i s t i n t o t h e t e s t s e c t i o n would need t o be a d j u s t e d f o r holdup of s a l t i n t h e l i n e connecting t h e pump bowl t o t h e f i r s t component i n t h e t e s t s e c t i o n .

The f r a c t i o n h e l d

up would d r a i n back i n t o t h e pump bowl or it would f r e e z e and s e t t l e out i n t h e l i n e , depending on whether or not t h e . l i n e w a s h e a t e d .

The flow

rate of s a l t m i s t i n t o t h e first t e s t component would be t h e flow rate out of t h e pump bowl t i m e s t h e f r a c t i o n n o t h e l d up i n t h e i n t e r v e n i n g I n comparing d a t a t a k e n over d i f f e r e n t t i m e i n t e r v a l s , t h e r e f o r e ,

line.

we make t h e a r b i t r a r y assumption t h a t f o r t h e p e r i o d s of i n t e r e s t , t h e flow rate of s a l t m i s t out of t h e pump bowl and t h e f r a c t i o n of s a l t

m i s t h e l d up i n t h e l i n e connecting t h e pump bowl t o t h e f i r s t component i n t h e t e s t s e c t i o n were e s s e n t i a l l y c o n s t a n t .

I n a d d i t i o n , we assume

t h a t t h e r e were no major changes i n t h e s i z e range and d e n s i t y of t h e

m i s t particles. Second, t h e c o l l e c t i o n rate determinations were s u s c e p t i b l e t o k r g e errors.

This i s because t h e q u a n t i t y of material c o l l e c t e d w a s u s u a l l y

on t h e o r d e r of 1 t o 10 g, while t h e weight of t h e c o l l e c t i o n component

w a s on t h e o r d e r of 100 t o 5000 g .

A 1% e r r o r i n weighing, t h e r e f o r e ,

would cause a 100% o r l a r g e r e r r o r i n t h e weight of material c o l l e c t e d . A n a t t e m p t w a s m a d e to a l l e v i a t e t h i s problem by making weighings on a

l a r g e a n a l y t i c a l b a l a n c e t h a t had a s e n s i t i v i t y of 0.02 g w i t h a 2000-g load. Third, t h e r e w a s some s e t t l i n g out or t r a p p i n g of s o l i d s i n t h e 5/16-in.-ID

l i n e s used t o connect t e s t components.

The d e p o s i t i o n w a s

g r e a t e r a t p l a c e s where a c c e l e r a t i o n f o r c e s were p r e s e n t , such as a t

90" bends.

I n c a s e s where t h e performance of an upstream component w a s

based on d a t a o b t a i n e d from downstream components, t h e f i g u r e s may be considered t o be i n e r r o r by some amount due to t h e t r a p p i n g of material i n t h e intervening l i n e s .

We do n o t have a n estimate of t h e s i z e of t h e

e r r o r i n t r o d u c e d by t h i s e f f e c t ; it would t e n d t o be i n d i r e c t p r o p o r t i o n t o t h e s o l i d s flow rate.

I n t h e series I1 t e s t s , t h e r e w a s a tendency

74 f o r s o l i d s t o accumulate i n t h e o u t l e t l i n e of t h e hot-mist t r a p upstream of t h e f i l t e r .

Where p o s s i b l e , t h i s material w a s c o l l e c t e d , and weights

were added t o t h e f i l t e r weights i n o r d e r t o determine t h e f i l t e r c o l l e c The tendency t o s e t t l e out on t h e s u r f a c e s of i n t e r c o n n e c t i n g

t i o n rates.

One would ex-

l i n e s may a l s o have a f f e c t e d t h e l i q u i d s c o l l e c t i o n d a t a .

p e c t t h e e r r o r t o be p r o p o r t i o n a l t o t h e amount of s o l i d s p r e s e n t s i n c e t h i s might g r e a t l y i n c r e a s e t h e a v a i l a - s l e s u r f a c e . I n t h e f i r s t series of t e s t s (Table 9 ) , t h e o f f - g a s l i n e between t h e pump bowl and t h e f i r s t t e s t component w a s normally c o l d and t h e s o l i d s c o l l e c t i o n d a t a are biased low because of t h e f r a c t i o n r e t a i n e d i n t h e O f t h e t o t a l material c o l l e c t e d i n tb-e s e t t l i n g t a n k and f i l t e r

line.

during t e s t Ia, about

9 6 was

r e t a i n e d i n tk-e s e t t l i n g tank.

W e can

p r e d i c t from Stokes l a w t h a t p a r t i c l e s l a r g e r t h a n 1 0 ~1 should have remained i n t h e s e t t l i n g t a n k (assumtng s p h e r i c a l p a r t i c l e s of d e n s i t y 2.0 g/c$

)

After t h e t e s t , t h e s o l i d s w e r e p i l e d up under t h e i n l e t

nozzle,? s o i f t h e assumptions r e g a r d i n g p a r t i c l e s i z e and d e n s i t y are reasonable, it appears t k a t t h e average p a r t i c l e s i z e may have been s i g n i f i c a n t l y l a r g e r t h a n 10 p or i n e r t i a l f o r c e s due t o t h e r e l a t i v e l y high

inlet velocity

(1.6 f p s )

may have had a pronouinced e f f e c t .

The s o l i d s

were t a n and tended t o " t a l l up" o r s t i c k t o g e t h e r i n clumps ( r a t h e r t h a n t h e b r i l l i a n t white free flowicg appearance c h a r a c t e r i s t i c of NaBF4-NaF powder)

W e a t t r i b u t e t h i s u n c h a r a c t e r i s t i c appearance t o a d s o r p t i o n of

a c i d vapors er,d c o r r o s i o n p r o d u c b t h a t were emitted from t h e pump bowl along with t h e sal% m i s t . I n t e s t Ik t h e c o l l e c t i o n rate i'or impactor 1-1 w a s about f i v e times t h a t f o r t h e s e t t l i n g t a n k i n t e s t Ia; t h e c o l l e c t i o n rate f o r impactor 1-2 w a s only akout o n e - t e n t h t h a t of t h e s e t t l i n g t a n k .

I n t e s t IC,when

only a f i l t e r w a s used, t h e c o l l e c t i o r , rate w a s even lower t h a n t h a t of impactor 1-2. anomalous.

W e c o n s i d e r t h e r e s d t s of t e s t s Ib and ICt o be completely

There w a s no reason t o expect any d i f f e r e n c e i n performance

between t h e two impactors because t h e y d i f f e r e d only i n t h e diameter and l e n g t h of t h e housing.

And t h e c o l l e c t i o n rate i n t e s t IC should have

been t h e h i g h e s t of a l l , because a high e f f i c i e n c y f i l t e r w a s used.

W e

a t t r i b u t e t h e s e s t r a n g e r e s u l t s t o holdup of s a l t m i s t a t t h e pump bowl off-gas o u t l e t nozzle and i n t h e i n t e r v e n i n g l i n e s .

If t h e cumulative

75 t o t a l of s o l i d s c o l l e c t e d during t h e series I t e s t s (191 g ) i s d i v i d e d by t h e t o t a l c i r c u l a t i n g t i m e (1900 h r ) , a v a l u e of 0 . 1 g / h r i s o b t a i n e d f o r t h e average c o l l e c t i o n r a t e .

This should r e p r e s e n t a lower l i m i t f o r

t h e flow rate of s a l t m i s t i n t o t h e t e s t s e c t i o n .

If t h e c a l c u l a t i o n i s

r e p e a t e d u s i n g only t h e numbers from t e s t s Ia and I k

(182/830), we

get

an average v a l u e of 0.2 g / h r , which we f e e l i s probably t h e b e s t e s t i m a t e

w e can o b t a i n from t h e t e s t d a t a f o r t h e rate a t which s a l t m i s t w a s flowing from t h e pump bowl.

I n e v a l u a t i n g t h e s e r i e s I1 and I11 t e s t s ,

we assume t h a t t h e flow rate of s a l t m i s t from t h e pump bowl w a s c o n s t a n t a t 0.2 g / h r and t h a t t h e holdup i n t h e l i n e between t h e pump bowl and t h e salt-mist t r a p w a s c o n s t a n t ; t h u s t h e performance of t h e hot-mist t r a p s w a s d i r e c t l y p r o p o r t i o n a l t o t h e s o l i d s c o l l e c t i o n rate i n t h e f i l t e r s .

Table 9 shows t h a t t h e s o l i d s c o l l e c t i o n rates i n t h e f i l t e r s during t h e series I1 t e s t s were only 10,t o

15% of t h e rate (0.2 g / h r ) a t which

t h e s a l t m i s t w a s e s t i m a t e d t o b e l e a v i n g t h e pump bowl.

As noted p r e -

v i o u s l y , t h e s e f i l t e r c o l l e c t i o n r a t e s i n c l u d e t h e material found i n t h e l i n e between t h e hot-mist t r a p and t h e f i l t e r .

Note, however, t h a t i n

t e s t IIa, 9 g of s o l i d s were found i n t h e c o o l upper p a r t of t h e hot-mist If t h i s material w a s added t o t h e f i l t e r c o l l e c t i o n r a t e , t h e c o l -

trap.

l e c t i o n rate f o r t e s t IIa would be i n c r e a s e d almost 50%. W e conclude from t h e s e r i e s I1 t e s t s t h a t a s i g n i f i c a n t r e d u c t i o n i n t h e t r a n s f e r of

s a l t m i s t t o t h e f i l t e r s w a s achieved i n t h e c a s e of a l l t h r e e models. The f r a c t i o n of s a l t m i s t t h a t w a s t r a n s m i t t e d , however, t e n d e d t o c o l l e c t i n t h e l i n e upstream of t h e f i l t e r , and, i n ' t h e case of t e s t I I c , these accumulations r e s u l t e d i n severe f l o w r e s t r i c t i o n s . Table 9 a l s o shows t h a t t h e c o l l e c t i o n d a t a f o r t h e s e r i e s 111 t e s t s i n c l u d e q u a n t i t i e s c o l l e c t e d i n t h e h o r i z o n t a l m i s t t r a p s (â&#x201A;ŹD"-Hl, HMT-H2, and HMT-H3).

T h i s w a s s a l t t h a t passed through t h e h o t d e m i s t e r element

b u t w a s r e t a i n e d i n t h e hot-mist t r a p on t h e downstream side of t h e h o t d e m i s t e r element r a t h e r t h a n b e i n g c a r r i e d o u t w i t h t h e o f f - g a s stream. For purposes o f e v a l u a t i n g performance, t h i s material must be added t o t h e material c o l l e c t e d i n t h e f i l t e r s . the

A q u a l i f i c a t i o n i s necessary i n

case of t e s t I I I c , however, because t h e h o r i z o n t a l m i s t t r a p con-

t a i n e d a c o o l zone f i l t e r element t h a t w a s n o t used i n t h e IIIa and IIrU models.

W e were not a b l e t o measure t h e amount of material r e t a i n e d on

t h i s cool zone element, b u t v i s u a l i n s p e c t i o n i n d i c a t e d t h a t t h e q u a n t i t y If t h e q u a n t i t y had been 1 g o r more, it should have been

w a s small.

h i g h l y v i s i b l e , s o we decided f o r comparison purposes t o use a v a l u e of 1 g o r 0.001 g / h r f o r t h e 1000-hr p e r i o d .

Considering t h e s e f a c t o r s t h e

c o l l e c t i o n rates were 0.02, 0.01 ( n e a r l y ) , and 0.03 g / h r , r e s p e c t i v e l y , f o r t e s t s IIIa, IIIb, and I I I c .

W e conclude t h a t t h e e f f i c i e n c y of t h e

h o r i z o n t a l hot-mist t r a p s w a s about t h e same as t h a t of t h e v e r t i c a l h o t

mist.

The h o r i z o n t a l hot-mist t r a p s , however, gave l e s s d i f f i c u l t y

with flow r e s t r i c t i o n s (due t o s a l t ) , a p p a r e n t l y because t h e s a l t m i s t which passed through t h e h o t d e m i s t e r element w a s r e t a i n e d i n t h e m i s t t r a p housing.

I n t e s t I I I c , t h i s material w a s found a t t h e bottom of t h e

housing i n t h e form of s o l i d i f i e d d r o p l e t s r a t h e r t h a n c r y s t a l s o r powder which one would expect if f r o z e n s a l t p a r t i c l e s had s e t t l e d out from t h e gas stream.

W e conclude t h a t t h i s accumulation of material r e s u l t e d from

t h e d r a i n i n g o f d r o p l e t s of s a l t from t h e downstream s u r f a c e of t h e h o t

demister element.

I f t h i s i s trGe, t h e n t h e e f f i c i e n c y of t h e h o r i z o n t a l

hot-mist t r a p s may have been h i g h e r t h a n w a s i n d i c a t e d by t h e c o l l e c t i o n data.

Except f o r t h e l a t t e r p a r t of t h e series I t e s t s , t h e o f f - g a s stream

w a s passed t h r o w h a wet-ice c o l d t r a p (CT-WI) d u r i n g t h e e n t i r e t e s t program, and a v i s c o u s dark-brow- fl-did w a s r o u t i n e l y accumulated.

The f i n a l

t e s t i n t h e program ( I I I d ) w a s designed t o determine how t h e l i q u i d c o l l e c t i o n rate would be a f f e c t e d b;- a s l u g of water i n j e c t e d i n t o t h e s a l t pool i n t h e p u p 3 o w l .

For t h i s t e s t a d r y - i c e - t r i c h l o r o e t h y l e n e

D I ) w a s used as a backup f o r t h e w e t - i c e t r a p . are summarized i n Table 9 .

t r a p (CT-

The l i q u i d c o l l e c t i o n d a t a

It may b e seen from t h e t a b l e t h a t t h e l i q u i d

c o l l e c t i o n r a t e v a r i e d randomly between 0.005 and 0.009 g / h r over t h e

7500 h r of o p e r a t i o n , as though t h e emission was due t o t h e continuous i n t r o d u c t i o n of a contaminant (such as w a t e r i n t h e BF, or helium gas supply).

Thus, if t h e contaminant i s considered t o be water and t h e a v e r -

age c o l l e c t i o n i s assumed t o be 0.007 g/hr, t h e n t h e r e q u i r e d volumetric i n p u t of water would be

(0.007 hr

g )(?2.4

l i t e r s / l 8 g)

= 0.0087 l i t e r s / h r

77 W

If t h e gas flow i s

F l i t e r s / h r and t h e c o n c e n t r a t i o n of water i s C ppm,

t h e n t h e r e q u i r e d c o n c e n t r a t i o n would be (C X

from which C = 8700/F.

l i t e r / l i t e r ) ( F l i t e r / h r ) = 0.0087

If we apply t h e normal gas flow rates t o t h i s

e q u a t i o n , t h e r e s u l t s are as f o l l o w s :

Gas

Normal flow (liters/hr )

1900

100

BF3

Helium

R e q u ir e d c o n c e n t r a t i o n of i n t h e gas

If we assume t h a t t h e t r a p p e d f l u i d i s BF3.2H,0 r a t h e r t h a n %O,

then

only one-fourth as much water would be r e q u i r e d and t h e r e q u i r e d i m p u r i t y c o n c e n t r a t i o n would be

475

ppm f o r BF,

and 25 ppm f o r helium.

Analysis

of t h e BF3 gas i n d i c a t e d t h a t t h e water c o n c e n t r a t i o n w a s less t h a n 1 ppm. The w a t e r c o n t e n t of t h e helium w a s supposed t o be less t h a n 1 ppm, b u t samples t a k e n from t h e helium supply header a t t h e t e s t f a c i l i t y f r e q u e n t l y i n d i c a t e d water l e v e l s of as much as 25 ppm.

We concluded t h e r e f o r e t h a t

t h e helium gas supply w a s most probably r e s p o n s i b l e f o r t h e continued lowl e v e l emission of condensable f l u i d i n t h e o f f - g a s stream.

The conclusion

w a s r e i n f o r c e d d u r i n g t h e p o s t - t e s t e x a m i n a t i o n of t h e pump, when e v i d e n c e

of severe e r o s i o n w a s noted on t h e i n n e r h e a t b a f f l e s n e a r t h e p o i n t where t h e s h a f t purge gas helium e n t e r e d t h e pump (see S e c t .

5.4.4

6 .lo).

General conclusions from o f f - g a s t e s t s The f o l l o w i n g i s a summary of t h e p e r t i n e n t conclusions r e s u l t i n g

from e v a l u a t i o n of t h e o f f - g a s system t e s t s . 1. The p r e v e n t i o n of flow r e s t r i c t i o n s due t o salt-mist d e p o s i t s r e q u i r e s a t w o f o l d approach.

F i r s t , a hot-mist t r a p , t h a t i s , one t h a t

o p e r a t e s above t h e s a l t m e l t i n g p o i n t , would be i n s t a l l e d a t t h e pump W

bowl o u t l e t t o remove as much of t h e s a l t m i s t as p o s s i b l e from t h e gas

78 stream.

The f r a c t i o n of s a l t m i s t removed would b e e i t h e r r e t u r n e d t o t h e

pump bowl or s t o r e d u n t i l it could ise r e t u r n e d t o t h e system or d i s c a r d e d . Second, t h e gas emerging from t h e hot-mist t r a p would b e c h i l l e d t o freeze r e s i d u a l s a l t p a r t i c l e s and t h e n passed through a f i l t e r t o remove t h e frozen p a r t i c l e s . eration.

The hot-mist t r a p would b e designed f o r continuous op-

The p a r t i c l e f i l t e r would be arranged s o t.hat t h e f i l t e r u n i t

or t h e f i l t e r i n g material could be r e p l a c e d when n e c e s s a r y .

The p i p e l i n e

between t h e pump bowi o u t l e t and t h e hot-mist t r a p would be o p e r a t e d a t a

temperature above t h e s a l t melting p o i n t and would have a continuous rev e r s e p i t c h t o permit d e e n t r a i n e d s a l t t o d r a i n back i n t o t h e pump bowl. 2.

The salt-mist overflow, t h a t is, t h e f r a c t i o n (based on t h e flow

rate of salt m i s t a t t h e pump kowl out;&)

of s a l t m i s t n o t removed by t h e

hot-mist t r a p , w a s 15% or less f o r a l l t h e hot-mist t r a p models t e s t e d . This would imply 285% r e n o v a l e f f i c i e n c y , b u t it w a s n o t c l e a r what p a r t of t h e removal w a s due t o t k e demisting a c t i o n o f the h o t - m i s t t r a p and

what p a r t

WRS

due t o g r a v i t a f f o n a l s e t t l i n g i n t h e p i p e connecting t h e

pump bowl t o t h e hot-mist t r a p .

O f t k e d i f f e r e n t d e m i s t e r mechanisms

t e s t e d , t h e one u s i n g a porous metal s c r e e n ( F e l t Metal 225 by Huyck, I n c . ) appeared t o have an advantage i n t h a t t h e p r e s s u r e drop remained a c c e p t a b l y low over 1000 h r of o p e r a t i o n and most of t h e salt, which passed through t h e screen s e t t l e d

as d r o p l e t s i n t h e t r a p .

The f i l t e r element f o r t h e p m t i c l e f i l t e r should be f a b r i c a t e d

from a porous metal scree!:

( s u c h as Huj-ck Felt Metal) t h a t h a s a removal

r a t i n g , i n g;as s e r v i c e , cf not less thar?, 9'3$ of p a r t . i c l e s l a r g e r t h a n 1 g . This material should be s t a i n l e s s s t e e l .

I n t h e o p e r a t i o n of t h e p a r t i c l e f i l t e r , t h e f r o z e n s a l t p a r t i c l e s

may t e n d t o s e t t l e out i n t h e r e g i o n upstream of t h e f i l t e r element.

minimize flow r e s t r i c t i o c problems i n t h i s area, t h e d i s t a n c e between t h e hot-mist t r a p and t h e p a r t i c l e f i l t e r should b e kept as s h o r t as p o s s i b l e , and t h e connecting p i p e should be of uniform c r o s s s e c t i o n and, i f p o s s i b l e , without bends.

I s o l a t i o n v a l v e s should be h a l l or g a t e t y p e .

The continuous l o w - l e v e l emissions of v i s c o u s brown f l u i d were

probably caused by moisture l e v e l s of about 25 ppm i n t h e helium supply gas.

The presence of t h i s v i s c o u s f l u i d i n t h e o f f - g a s stream a t t h i s

79 W

low l e v e l (0.007 g/hr o r about 0.0001 g / l i t e r ) d i d n o t cause an o p e r a t i n g problem ( e . g . ,

salt m i s t .

s t i c k i n g p r e s s u r e c o n t r o l v a l v e ) as long as t h e r e w a s no

Since c o r r o s i o n rates i n f l u o r o b o r a t e systems are d i r e c t l y

p r o p o r t i o n a l t o t h e water l e v e l , t h e helium supply system should c o n t a i n

a d r y e r designed t o maintain t h e moisture c o n t e n t a t a v e r y low l e v e l , with a n upper l i m i t of 1 ppm by volume.

CHRONOLOGY, PERTINENT OBSEFWATIONS, AND OTHER TESTS

6 . 1 Chronology Planning f o r t h e t e s t program w a s s t a r t e d i n

mid-1967.

By t h e end

of t h a t y e a r , a t e n t a t i v e program had been formulated, and work w a s i n p r o g r e s s on t h e necessary f a c i l i t y m o d i f i c a t i o n s .

Figure 29 i s a chrono-

l o g i c a l summary of t e s t a c t i v i t i e s s t a r t i n g with January 1968.

Four

689 l b , were charged i n t o t h e d r a i n t a n k d u r i n g I n i t i a l f i l l i n g and s a l t c i r c u l a t i o n occurred on March 4, 1968.

b a t c h e s of s a l t , t o t a l i n g February.

Loop o p e r a t i o n w a s d i v i d e d i n t o a f l u s h i n g s a l t p e r i o d , extending from March through June

1968, and a main t e s t p e r i o d , extending from August

1968 through A p r i l 1970. The f l u s h i n g s a l t o p e r a t i o n w a s o r i g i n a l l y scheduled t o be completed i n about a week.

However, a number of problems a r o s e t h a t r e q u i r e d s t u d y

and r e s u l t e d i n s e v e r a l shutdowns f o r r e p a i r s and d e s i g n changes, and t h i s phase of t h e t e s t l a s t e d about ll5 days.

The following i s a b r i e f

d i s c u s s i o n of s i g n i f i c a n t e v e n t s . 1. While running c a v i t a t i o n t e s t s , a number of i n g a s s i n g t r a n s i e n t s

occurred when t h e pump c a v i t a t e d a t unexpectedly h i g h o v e r p r e s s u r e s (see Sect.

4.1

and Table 10). I m p e l l e r i n g a s s i n g i s t h e pumping of gas from

t h e pump t a n k along t h e t o p s i d e of t h e pump i m p e l l e r and i n t o t h e c i r c u l a t i o n system s a l t .

It i s g e n e r a l l y thought t o occur whenever t h e head

produced by t h e working i m p e l l e r i s lower t h a n t h a t produced by t h e i m p e l l e r t o p s u r f a c e and i s caused by pump o p e r a t i o n e i t h e r a t e x c e s s i v e flow rates o r i n deep c a v i t a t i o n .

When an i n g a s s i n g t r a n s i e n t occurred,

t h e r e was a sudden i n c r e a s e i n c i r c u l a t i n g volume, and this i n t u r n V

caused a r i s e i n s a l t l e v e l i n t h e pump t a n k .

The pump w a s s h u t o f f

w i t h i n a f e w seconds, which stopped t h e i n g a s s i n g , b u t t h e t r a n s i e n t s

O R N L - O W G 72-2091

INSTALL HOT MIST TRAP FINISH UP SYSTEM REVISIONS CHECK OUT SYSTEM TRANSFER SALT INTO DRAIN TANK -CCT CAVITATION TESTS -FLUSHING SALT PUMP INGASSING GAS LINE PLUGGING PROBLEMS INSPECT PUMP ROTARY ELEMENT GREEN SALT REVISE OFF-GAS VENTING SYSTEM INSTALL MIXED-GAS B F j FEED -CCT

5825 hr

COLD FINGER TESTS MIST TRAP TESTS

973hr

REMOVE FLUSHING SALT TRANSFER CLEAN SALT TO SYSTEM

-CCT

8692 hr

CAVITATION TESTS-CLEAN SALT COMPOSITION CONTROL TESTS MIST TRAP TESTS -CCT

2787 hr

INSTALL OFF-GAS TEST SECTION AT PUMP BOWL OUTLET -CCT OFF-GAS FILTER TESTS

-CCT

11,089 hr

}WATER INJECTION TEST

4 6 8 0 hr

INITIAL CIRCULATION MAR. 4. 1968 FINAL DRAIN APR. 13, I970 TOTAL ELAPSED TIME 18,480 hr

CIRCULATING TIME (hr) FLUSH SALT 973 CLEAN SALT (0.594 TOTAL (1.567

CCT = CUMULATIVE CIRCULATING TIME

Fig. 2 9 .

Chronology

- sodium

fluoroborate c i r c u l a t i o n t e s t .

81. W

were s u f f i c i e n t l y r a p i d and enough gas w a s i n g e s t e d s o t h a t t h e pump t a n k

w a s f i l l e d with s a l t and s a l t w a s f o r c e d i n t o t h e connecting unheated gas lines.

Each t r a n s i e n t , t h e r e f o r e , r e s u l t e d i n a program d e l a y for c l e a n -

out o r replacement of plugged gas l i n e s .

Table 10.

I n g a s s i n g t r a n s i e n t s f o r NaBF4 c i r c u l a t i o n t e s t , PKP l o o p

Pump time ( h r )

Date

Item Cmulat ive

3-7-68 3-13-68

Net

Ingass i n g t r a n s i e n t

Ingassing t r a n s i e n t Remove, i n s p e c t , and r e i n s t a l l r o t a r y element; discovery of f i r s t d e p o s i t of green s a l t

4-9-68

187

5-28-68 6-18-68 6-24-68

472

285

Ingassing t r a n s i e n t

736

264

Ingassing t r a n s i e n t

872

136

Ingassing t r a n s i e n t

Continuing d i f f i c u l t y w a s experienced w i t h gas l i n e r e s t r i c t i o n s .

The t r o u b l e w a s due i n p a r t t o t h e i n g a s s i n g t r a n s i e n t s , which f o r c e d s a l t i n t o t h e pump bowl gas connections, and i n p a r t t o s a l t i m p u r i t i e s and s a l t m i s t w h i c h w e r e being s w e p t out of t h e pump b o w l by t h e purge-gas

stream (see S e c t . 5 . 4 ) .

The pump r o t a r y element w a s removed t o check f o r an o i l l e a k .

No leak w a s found, and t h e apparent l o s s of o i l from t h e l u b e - o i l reserv o i r w a s a t t r i b u t e d t o a s h i f t of i n v e n t o r y from t h e r e s e r v o i r t o t h e pump b e a r i n g c a v i t y .

When t h e pump r o t a r y element w a s removed for i n s p e c -

t i o n , s e v e r a l l a r g e chunks of green s a l t were found l y i n g on t o p of t h e i m p e l l e r c a s i n g ( s e e S e c t . 6.11 f o r f u r t h e r d e t a i l s on t h i s material).

BF, w a s normally f e d t o t h e system through a b u b b l e r d i p t u b e

i n s e r t e d i n t h e pump bowl.

The back p r e s s u r e i n t h e t u b e w a s a l s o used

as a n i n d i c a t o r of pump bowl s a l t l e v e l .

It w a s d e s i r e d t o keep t h e

b u b b l e r flow uniform i n o r d e r t o avoid t h e need for l e v e l c o r r e c t i o n s

due t o flow v a r i a t i o n s and t o keep t h e bubbler flow rate about t h e same

as t h a t used i n t h e MSRE c o o l a n t pump (370 c$/min)

f o r simulation.

The

o r i g i n a l c a l c u l a t i o n s i n d i c a t e d t h a t a BF3 flow of about 300 cn?/min would be r e q u i r e d , and t h e system w a s designed on t h i s b a s i s .

Subse-

quently, an i n c r e a s e was made i n t h e normal s e t t i n g f o r t h e pump bowl t o t a l overpressure, and r e v i s e d BF3 p a r t i a l p r e s s u r e d a t a were received; t h e s e changes reduced t h e normal BF3 flow r a t e ( a t 1025째F) t o 50 c$/min. I n o r d e r t o maintain t h e d e s i r e d t - o t a l flow, a mixed-gas system was i n s t a l l e d i n which t h e t o t a l flow w a s c o n t r o l l e d a t 370 c$/min,

and t h e

composition of t h e gas mixture ( r a t i o of BF3/He) w a s a d j u s t e d as d i c t a t e d by t h e s a l t temperature, t h e pump bowl t o t a l o v e r p r e s s u r e , and t h e t o t a l gas flow.

The mixed-gas BF3 f e e d system w a s i n s t a l l e d d u r i n g t h e shutdown

f o r i n s p e c t i o n of t h e s a l t pump r o t a r y element; S e c t i o n 5.5 d e s c r i b e s t h e gas system as it appeared a f t e r t h i s change w a s made.

The use of a mixed-

gas BF3 meant t h a t t h e normal gas composition i n the b u b b l e r t u b e ( a t

1025째F) was about 12.5% EF3 by volume, whereas t h e normal composi+,ion ( a t 1025째F and 24 p s i g ) of t h e pump howl atmosphere w a s about 3.5% by volume. See S e c t i o n 6.5 f o r a d i s c u s s i o n of t h e e f f e c t of gas composition on bubbler t u b e o p e r a t i o n . Duricg 2uly and August

1968, t h e f l u s h i n g sait. (702 lb) w a s t r a n s -

ferred out of t h e system and r e p l a c e d w i t h a f r e s h charge of sodium fluoroborate

(765

lb).

Pretreatment of t h e f r e s h charge w a s modified i n

an attempt t o reduce t h e wa%er c o c t e n t ( S e c t . 6 . 3 ) . w i t h t h e c l e a n charge of s a l t w a s on August 19,

I n i t i a l circnlation

1963. September and

October 1968 were s p e n t i n performing c a v i t a t i o n t e s t s and i n e v a l u a t i n g t h e performance of t h e t h e r m 1 c o n d x t i v i t y cell t o i n d i c a t e salt composition.

A s e v e r e r e s t r i c t i o n i n t h e o f f - g a s l i n e a t t h e pump bowl o u t l e t

f o r c e d a shutdown of t h e l o o p on November

4, 1968.

The o f f - g a s p i p i n g

w a s r e v i s e d t o provide a t e s t s e c t i o n f o r st*udying t h e problem of o f f - g a s r e s t r i c t i o n s , and o p e r z t i o n s were resumed on December 19, 1969.

From t h a t

p o i n t u n t i l t h e fir,al shutdown i n A p r i l 1970, t h e p r i n c i p a l a c t i v i t i e s

were e v a l u a t i o n of t h e c o l d zone d e p o s i t i o n t e c h n i q u e ( S e c t . 5.3) and e v a l u a t i o n of v a r i o u s t e c h n i q u e s f o r coping w i t h t h e problem of o f f - g a s system r e s t r i c t i o n s ( S e c t .

5.4).

The t o t a l s a l t c i r c u l a t i o n t i m e w a s

11,567 h r , of which 973 h r were w i t h t h e f l u s h i n g s a l t , From March 1968 u n t i l November 1968, t h e set p o i n t f o r t h e c i r c u l a % i n g s a l t temperature

w a s v a r i e d f r e q u e n t l y t o accommodate c a v i t a t i o n i n c e p t i o n t e s t s and o t h e r s p e c i a l t e s t s ; s e t t i n g s used d u r i n g t h i s t i m e i n t e r v a l were 900, 1025, A f t e r November 1968, t h e s a l t c i r c u l a t i n g temperature

1150, and 1275째F.

w a s maintained a t a c o n s t a n t s e t t i n g of 1025째F.

I n September 1970, t h e

pump r o t a r y element and t h e s a l t l e v e l bubbler t u b e were removed from t h e Findings a r e summarized i n S e c t i o n 6.10.

system for i n s p e c t i o n .

6.2

Analyses of S a l t Samples

Samples of s a l t were t a k e n from t h e pump bowl u s i n g equipment as des c r i b e d i n S e c t i o n 4.3.

T h i r t e e n samples were t a k e n d u r i n g t h e f l u s h i n g

salt period, t h r e e i n d u p l i c a t e .

S i x t e e n samples of t h e c l e a n b a t c h w e r e

t a k e n , a l l b u t one i n d u p l i c a t e .

Routine s a l t samples w e r e n o t t a k e n

a f t e r June 1969.

Normally t h e samples were t r a n s f e r r e d t o t h e a n a l y t i c a l

l a b o r a t o r y i n a covered g l a s s jar t h a t had been f l u s h e d w i t h argon.

Sam-

p l e s t a k e n d u r i n g and a f t e r A p r i l 1969 were d e l i v e r e d t o t h e a n a l y s t without removing them from t h e p r o t e c t i v e p i p e housing t h a t i s p a r t of t h e sampling u n i t .

The purpose w a s t o i n s u r e m a x i m u m p r o t e c t i o n a g a i n s t ex-

posure t o moisture i n t h e atmosphere.

I n a d d i t i o n t o t h e r o u t i n e samples,

a number of s p e c i a l samples were t a k e n during t h e t e s t program, mostly t o i d e n t i f y materials found i n t h e o f f - g a s system.

A l l pump bowl samples were analyzed for N a , B, and F and f o r t h e common c o r r o s i o n c o n s t i t u e n t s Fe, Cr, N i , and 0.

A number of t h e samples

were analyzed for t h e c o n s t i t u e n t s of t h e s a l t formerly used i n t h e l o o p ( L i , Be, U, and Th), and samples t a k e n d u r i n g and after A p r i l 1969 were analyzed for H 2 0 .

Average a n a l y t i c a l v a l u e s f o r t h e b a s i c c o n s t i t u e n t s

are shown below.

Concentration ( w t %) Na -

B -

Flushing s a l t

21.2

9.26

Clean s a l t

20.9

9.33

66.9 68.0

0.20

0.18

0.26

0.21+

0.048

0.016

0.019

0.093

Values f o r t h e i m p u r i t i e s found i n t h e s a l t samples are p l o t t e d i n Fig. 30.

The oxygen r e s u l t s w e r e q u i t e s c a t t e r e d and d i d not seem t o

c o r r e l a t e w i t h anything i n p a r t i c u l a r . f o r H,O,

Only a f e w samples were analyzed

and t h e l e v e l seemed t o i n c r e a s e w i t h t i m e .

Except f o r t h e

high-temperature o p e r a t i n g p e r i o d following a d d i t i o n of t h e c l e a n s a l t t o t h e system i n August

tive.

1968, t h e results f o r Fe, Cr, and N i were r e p e t i -

The c o n c e n t r a t i o n of n i c k e l w a s c o n s i s t e n t l y v e r y low.

The concen-

t r a t i o n of chromium i n t h e c l e a n s a l t s t a r t e d out about t h e same as t h e c o n c e n t r a t i o n i n t h e f l u s h s a l t , b u t t h e n l e v e l e d o f f a t about twice t h i s value.

The i r o n c o n c e n t r a t i o n i n t h e c l e a n s a l t w a s uniformly about

twice t h a t i n t h e f l u s h s a l t .

6.1 .,

Pretreatment and T r a n s f e r of S a l t Charges v

Pretreatment of t h e s a l t f o r removal of v o l a t i l e s and m e l t i n g , mix-

ing, and t r a n s f e r of t h e s a l t w e r e a l l done u s i n g a mobile u n i t t h a t w a s p o s i t i o n e d next t o t h e f a c i l i t y e n c l o s u r e .

The u n i t ( F i g s . 31 and 32)

contained a n i c k e l - l i n e d s t a i n l e s s s t e e l p o t of 2 f t 3 c a p a c i t y housed i n a 23-kW f u r n a c e .

Connections w e r e provided a t t h e t o p f o r charging of

s a l t and f o r t h e connection of vaculjm and i n e r t gas l i n e s .

The s a l t w a s

t r a n s f e r r e d through a 3/8-in.-OD t u b i n g l i n e t h a t w a s p r e h e a t e d by p a s s i n g e l e c t r i c c u r r e n t through t h e w a l l s of t h e t u b i n g .

The s i z e of t h e system

w a s such t h a t f o u r b a t c h e s were r e q u i r e d t o l o a d t h e sump t a n k . The procedure f o r p r e t r e a t m e n t and t r a n s f e r of t h e f l u s h i n g charge of s a l t w a s as f o l l o w s .

The c a l c u l a t e d amounts of s a l t powders, based

on t h e e u t e c t i c mixture, were loaded i n t o t h e m e l t i n g p o t through t h e 3-in. access pipe.

The p o t w a s s e a l e d up, h e a t e d t o 300°F, and h e l d

under a vacuum ( ‘1 p s i a ) f o r a t l e a s t 16 h r .

The f u r n a c e temperature

w a s t h e n raised t o 900°F ( m e l t i n g p o i n t of s a l t =

725°F) and i n e r t gas

blown through t h e d i p l e g f o r about 10 min t o i n s u r e good mixing of t h e charge.

The t r a n s f e r l i n e w a s t h e n connected t o t h e d i p l e g and t h e s a l t

t r a n s f e r r e d i n t o t h e sump t a n k by applying gas p r e s s u r e t o t h e m e l t i n g pot. P r i o r t o t h e a d d i t i o n of t h e f l u s h charge of s a l t , a temporary d i p l e g t u b e w a s i n s e r t e d i n t o t h e sump t a n k , and gas p r e s s u r e w a s used t o

xLk#!!!iL

APR

I I

m MAY

1 --1 /

JUN

JUL

--_--

- . _-

_. . ..-

1 I

PROFILE OF SALT CIRCULATION-INTERNAL

mjy//'/.y //kJ <///,'/A, AUG I SEPT 1 OCT

I +

Id-

~~~

MAR

PROFILE OF SALT TEMPERATURE

I/I

VERTICAL LINES INDICATE BRIEF SH

MAR

Fig. 30. Analyses of i m p u r i t i e s i n NaBF4 s a l t samples, f l u o r o b o r a t e c i r c u l a t i o n t e s t , PKP loop.

-T--

ORNL-DWG

72-2092

OFF-GAS

,-SALT

PUMP

--MAIN LOOP ENCLOSURE

1 EXHAUST FANEQUALIZING INERT GAS

VACUUM PUMP

7 NICKEL-LINED STAINLESS STEEL

TANK

POT

\ ‘-SALT

Fig. 31.

FURNACE 23 kW

Schematic diagram or s a l t t r a n s f e r system.

Fig. 32.

S a l t t r a n s f e r system.

88 blow t h e o l d BULT-4 s a l t from t h e sump t a n k i n t o a 55-gal s t e e l drum. f l u s h charge of s a l t w a s l a t e r removed t h e same way.

The

The c l e a n charge of

s a l t w a s processed e s s e n t i a l l y t h e same way as t h e f l u s h charge, except t h a t t h e BF,

p a r t i a l p r e s s u r e of t h e b a t c h a t 925째F w a s used as a c r i t e r i o n

f o r t h e e f f e c t i v e n e s s of t h e evacuation t r e a t m e n t .

r i s e w a s a r b i t r a r i l y s e l e c t e d as 10 p s i . showed p r e s s u r e rises of cessing.

The l i m i t i n g p r e s s u r e

Three of t h e f o u r b a t c h e s t h a t

4 t o 6 p s i were t r a n s f e r r e d without f u r t h e r pro-

The remaining b a t c h , which r e g i s t e r e d a 1 3 - p s i r i s e a t 925"F,

w a s cooled down and reevacuated, remelted, and t r a n s f e r r e d .

The p r e s s u r e

r i s e during t h e second m e l t w a s only 1 . 5 p s i .

All s a l t b a t c h e s were t r a n s f e r r e d without i n c i d e n t .

There w a s i n t e r -

m i t t e n t plugging of t h e d i p l e g during t h e process of mixing w i t h t h e helium stream (see S e c t . 6 . 5 ) .

The q u a n t i t i e s of material t r a n s f e r r e d are

given below.

Date of t r a n sf e r

Weight transferred Ob)

Flush charge added t o surnp tai.lk

Feb. 1968

687

Flush charge removed from sump t a n k

J u l y 1968

702

Clean charge added t o s m p t a n k

J u l y 1968

765

6.4

Freeze Valve ODeration

The f r e e z e v a l v e c o n s i s t e d of a 2-in.-long

squeezed-down s e c t i o n a t

t h e c e n t e r of a 1 2 - i n . - l o n g p i e c e of 3/4-in.-IFS sched-40 Inconel p i p e . Pipe w a l l spacing a t t h e narrow p a r t w a s c a t e d from a p i e c e of 1 1/2-in.-IPS system w a s minimal.

1/4 i n .

The a i r t u b e w a s f a b r i -

sched-40 Inconel p i p e .

The c o n t r o l

There w e r e thermocouples t o monitor t h e temperature

a t t h e c e n t e r of t h e v a l v e and a t t h e s h o u l d e r s and hand-operated Variacs t o a d j u s t h e a t e r power and a hand-operated v a l v e t o a d j u s t a i r flow. thermocouple and h e a t e r l a y o u t i s shown i n F i g . 33.

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

couples were added f o r t h e f l u o r o b o r a t e t e s t i n o r d e r t o o b t a i n b e t t e r s i m u l a t i o n of t h e MSRE freeze v a l v e s .

The

ORNL-DWG 72-2093

HEATER 2 9

- 4 x 9’/,-in

/” 4’

FLAT C E R A M I C

HEATERS ( 2 ) 3 5 0 W 115 V

HEATER 28 131~ID x 4 i n L O N G C L A M S H E L L (2) 0 5 0 W 115 V -._

, )-f

TO LOOP

,/;

’32-in

H E A T E R 30

CALRODS (2)

BETWEEN HEATERS

,! i n

TOP A N D B O T T O M 750 W 2 4 0 V

SclMP

FUEL L I N E

’14 i n BETWEEN HEATERS

x 3114 x

INSULATION WITH

SHIMSTOCK BETWEEN INSULATION AND HEATERS

F i g . 33. Heater and thermocouple l a y o u t d r a i n l i n e f r e e z e v a l v e , NaBF4 c i r c u l a t i o n t e s t , PKP loop.

The f r e e z e valve w a s o p e r a t e d through s i x f i l l and d r a i n c y c l e s during t h e f l u s h s a l t program and t e n f i l l and d r a i n c y c l e s d u r i n g t h e c l e a n s a l t program.

There w a s never any d i f f i c u l t y i n e s t a b l i s h i n g o r

thawing t h e f r o z e n s a l t plug i n t h e v a l v e .

The temperature a t t h e

c e n t e r of t h e v a l v e w a s maintained between 200 and 400째F while t h e v a l v e

was frozen.

The t i m e r e q u i r e d f o r d r a i n i n g v a r i e d between 3 min and

3 hr.

Although t h e l o n g e r d r a i n t i m e s w e r e a t t r i b u t e d to v a r i a t i o n s i n o p e r a t i n g techniques, an a l t e r n a t e p o s s i k i l i t y would be flow r e s t r i c t i o n s due t o accumulations of c o r r o s i o n p r o d u c t s .

The l a s t s i x d r a i n s a l l r e q u i r e d

7 t o 10 min, which i n d i c a t e s t h a t t h e s i t u a t i o n improved w i t h p r a c t i c e . On March 21, 1968, t h e freeze v a l v e was used t o pro5ect t h e d r a i n t a n k from e x c e s s i v e p r e s s u r e while making a c a l i b r a t i o n check on t h e s a l t pressure t r a n s m i t t e r s .

No p r e s s u r e r i s e w a s noted i n t h e d r a i n t a n k ,

which w a s a t 0 p s i g , during t h e 30-min p e r i o d when t h e l o o p w a s p r e s s u r i z e d w i t h helium a t varioils l e v e l s between 50 and 100 p s i g .

During t h e p r e p a r a t i o n of t h e charge of f l u s h s a l t i n t h e s a l t f u r nace ( S e c t . 6 . 3 ) , helium w a s buk,bled through a t u b e submerged i n t h e molten mass t o i n s u r e good mixing.

It w a s observed t h a t t h e gas-feed

p r e s s u r e would b u i l d up and drop o f f i n t e r m i t t e n t l y , as though t h e t u b e

w a s a l t e r n a t e l y plugging and unpluggirg.

The i m p l i c a t i o n w a s t h a t t h e

helium w a s s t r i p p i n g BFa away from t h e s a l t a t t h e end of t h e t u b e , l e a v i n g a high-melting XaF-enriched phase t h a t p r e c i p i t a t e d out and caused t h e flow r e s t r i c t i o n . I n September and October 1968, t h r e e t e s t s were r u n i n a n attempt t o confirm t h i s o b s e r v a t i o n . b l e r t u b e (see F i g .

I n each c a s e t h e BF3 flow t o t h e pump bowl bub-

7) w a s reduced t o z e r o and allowed t o remain t h e r e un-

til plugging of t h e t u b e w a s i n d i c a t e d , t h a t i s , u n t i l t h e i n d i c a t e d s a l t l e v e l went o f f s c a l e on t h e h i g h s i d e ( t h e aP a t f u l l s c a l e w a s 20 i n . HzO or 0.72 p s i ) .

While t h e BF3 flow w a s a t zero, t h e helium flow w a s

i n c r e a s e d s o as t o maintain t h e t o t a l bubbler flow a t 370 cr$/min.

s a l t temperature w a s mostly 900째F during two of t h e t e s t s and mostly

1025째F f o r t h e t h i r d t e s t .

Some v a r i a t i o n s i n s a l t temperature were

The

caused by o t h e r t e s t work t h a t w a s being c a r r i e d out a t t h e same t i m e . The BF3 flow w a s r e s t o r e d t o normal immediately a f t e r t h e i n d i c a t e d l e v e l went o f f s c a l e .

r e s u l t s (see F i g . 34) show t h a t where t h e

average temperature w a s 900째F, t h e bubbler t u b e plugged i n about

140 h r ,

and where t h e s a l t temperature was lO25"F, plugging occurred i n about

54 h r .

I n each case t h e salt l e v e l i n d i c a t i o n r e t u r n e d t o normal w i t h i n

an hour after t h e BF,

flow w a s r e s t o r e d .

The t i m e r e q u i r e d t o develop a

plug w a s less a t h i g h e r s a l t temperature, presumably because t h e h i g h e r BF,

p a r t i a l p r e s s u r e p e r m i t t e d more r a p i d removal of t h e BFa.

It i s

i n t e r e s t i n g t o n o t e t'nat t h e plugging t i m e r e q u i r e d during t h e s a l t p r e p a r a t i o n o p e r a t i o n w a s lower by a f a c t o r of more t h a n 100 t h a n t h e plugging t i m e r e q u i r e d during t h e bubbler t u b e t e s t .

A probable e x p l a -

n a t i o n i s t h a t t h e r e w a s much b e t t e r mixing i n t h e pump bowl due t o t h e r e l a t i v e l y h i g h rate of exchange of s a l t ( e s t i m a t e d t o be one l o o p v o l -

ume e v e r y 2 min) between t h e pump bowl and t h e b u l k s a l t c i r c u l a t i o n system.

Other c o n t r i b u t i n g f a c t o r s may have been t h e d i f f e r e n c e i n t u b e

geometry ( t h e s a l t t r a n s f e r t u b e w a s

1/4 i n .

I D , whereas t h e b u b b l e r t u b e

w a s 1 / 2 i n . I D ) or t h e gas flow i n t h e s a l t p r e p a r a t i o n t a n k ( a flowmeter w a s not used and s o t h e a c t u a l flow w a s not known) may have been s i g n i f i c a n t l y h i g h e r t h a n t h e b u b b l e r t u b e flow. Although t h e above t e s t s i n d i c a t e t h a t a continuous b u b b l e r flow cannot be maintained u s i n g pure helium, it must be concluded t h a t t h e use of a pure BF, nature.

flow might a l s o cause plugging problems of a d i f f e r e n t

A s a n example, assume o p e r a t i n g c o n d i t i o n s of 1025째F (BF, p a r t i a l

pressure =

1.35 p s i a ) , 24 p s i g , and a 100% BF3 f e e d t o t h e b u b b l e r .

Now,

assume t h e BF, flow i s i n a d v e r t e n t l y c u t o f f a t a v a l v e i n t h e BF3 h e a d e r . The BF,

downstream of t h e v a l v e will r e a c t w i t h t h e s a l t , and t h e header

p r e s s u r e w i l l approach t h e e q u i l i b r i u m v a l u e of

1.35 p s i a .

As t h e header

p r e s s u r e drops, s a l t w i l l be d r i v e n back through t h e bubbler t u b e , and t h e unheated p o r t i o n of t h e BF, salt.

feed header w i l l be plugged w i t h f r o z e n

100

-8

F A

ORNL-DWG 7 2 - 2 0 9 4

* A

L A

7 '

128 hr

a c3

0 w

1200 - -*

800 I

w I-

---

E 3

I--

600 18

SEPT. 1968

OCT. 1968

OCT 1968

F i g . 34. E f f e c t o f o p e r a t i n g l i q u i d l e v e l b u b b l e r t u b e without f l o w , NaBFt+ c i r c u l a t i o n t e s t , PKP loop.

6.6

Ekperience with S a l t Level Instruments

P r i o r t o t h e f l u o r o b o r a t e t e s t program, t h e l o o p was equipped w i t h f i v e s i n g l e - p o i n t , or s p a r k plug, s a l t l e v e l i n d i c a t o r s , one each for

m a x i m u m , minimum, and normal pwnp bowl l e v e l and one each f o r m a x i m u m and minimum d r a i n t a n k l e v e l .

The o p e r a t i n g p o t e n t i a l w a s 110 V, and

when s a l t c o n t a c t e d t h e probe, t h e c i r c u i t w a s c l o s e d , causing an i n d i c a t o r bulb t o l i g h t up.

The probe material w a s changed from Inconel t o

Hastelloy N f o r t h e fluoroborate service.

The normal and minimum l e v e l

probes i n t h e pump bowl were removed from s e r v i c e e a r l y i n t h e program i n o r d e r t o provide a c c e s s f o r o t h e r t e s t s .

The t h r e e remaining l e v e l

probes gave e x c e l l e n t s e r v i c e f o r t h e d u r a t i o n of t h e t e s t program.

The

only t r o u b l e w a s i n A p r i l 1968, when t h e d r a i n t a n k m a x i m u m probe s h o r t e d out.

The failure was t r a c e d t o a l e a k y t u b e f i t t i n g .

Wet a i r d i f f u s e d

i n through t h e l e a k , and t h e r e s u l t i n g accumulation of c o r r o s i o n products b r i d g e d t h e gap between t h e probe and t h e nearby v e s s e l w a l l . During normal o p e r a t i o n , a continuous i n d i c a t i o n of t h e pump bowl

salt level w a s provided by monitoring t h e back-pressure i n t h e EF3 f e e d l i n e (see F i g .

7).

The BF3 bubbler f e e d t u b e w a s 5/8-in.-OD by 0 . 0 6 5 - i n . -

w a l l Inconel t u b i n g welded i n t o t h e nozzle formerly occupied by t h e pump bowl minimum l e v e l probe.

The bottom of t h e b u b b l e r t u b e w a s 1 2 1 / 2 f n .

below t h e t o p of t h e nozzle; a s t u d y of t h e pump drawings i n d i c a t e s t h a t t h i s should have p l a c e d t h e t u b e end about line.

3/4 i n .

below t h e v o l u t e c e n t e r

The end of t h e t u b e had a s i n g l e 45" notch approximately

1/4 i n .

1/8 i n . deep. A t t h e normal o p e r a t i n g temperature of lO25OF, t h e salt d e n s i t y w a s 116 lbm/f't3 and t h e instrument range w a s 10.8 i n . s a l t

wide by

at f u l l scale.

During t h e e a r l y phases of t h e t e s t program, t h e s a l t

l e v e l w a s a d j u s t e d t o 25 t o

35% of t h e l e v e l s c a l e ; l a t e r on, t h e level

w a s a d j u s t e d t o 45 t o 50% t o i n s u r e t h a t t h e pump bowl thermocouple w e l l would be adequately covered w i t h s a l t .

I n normal o p e r a t i o n , a n upper

l i m i t of 54% (6 i n . s a l t ) w a s maintained on t h e s a l t l e v e l .

A backflow

p r e v e n t e r , a p i e c e of 1 1 / 2 - i n . - 1 ~ , g - i n . - l o n g s t a i n l e s s s t e e l p i p e , w a s i n s t a l l e d j u s t upstream of t h e b u b b l e r t u b e t o minimize plugging of t h e BF3 f e e d l i n e when p r e s s u r e l e v e l changes ( e . g . ,

d u r i n g pump i n g a s s i n g ) caused

backflow of s a l t from t h e pump bowl.

A Calrod h e a t e r w a s provided s o t h a t

any s a l t i n t h e backflow p r e v e n t e r could be melted and allowed t o d r a i n back i n t o t h e pump bowl.

Some d i f f i c u l t y w a s experienced with plugging

of t h e BF3 f e e d l i n e during t h e e a r l y p a r t of t h e l o o p o p e r a t i o n , b u t t h e plugs w e r e b e l i e v e d t o b e a s s o c i a t e d p r i m a r i l y w i t h t h e i n g a s s i n g t r a n s i e n t s t h a t occurred during c a v i t a t i o n t e s t s .

It w a s a l s o noted t h a t

plugging d i f f i c u l t i e s would occur i f t h e proper gas f e e d composition w a s n o t maintained.

J u s t p r i o r t o t h e f i n a l shutdown, a n apparent r i s e i n

s a l t l e v e l i n d i c a t e d t h a t t h e r e might be a flow r e s t r i c t i o n i n t h e bubbler Then a t t h e shutdown t h e r e s t r i c t i o n became worse, s o t h a t

tube l i n e .

t h e r e w a s a n apparent s a l t l e v e l even a f t e r t h e l o o p had been d r a i n e d . For t h e bubbler flow c o n d i t i o n s

(0.37 l i t e r / m i n ) , an o r i f i c e of about

0.030 i n . diameter (0.0036% of t h e o r i g i n a l c r o s s - s e c t i o n a l area) would be r e q u i r e d t o cause a d e t e c t a b l e change (21% s c a l e ) on t h e s a l t l e v e l

instrument . A f t e r shutdown, t h e b u b b l e r tiAbe w a s removed from t h e pump bowl. The end of t h e t u b e w a s found t o be completely f i l l e d w i t h a hard, g r a i n y , m e t a l l i c - a p p e a r i n g magnetic d e p o s i t ( s e e S e c t . 6.11).

Lesser amounts of

t h e d e p o s i t were found i n s i d e t h e t u b e as f a r as 5 1 / 2 i n . from t h e end.

W e conclude t h a t t h e performance of t h e b u b b l e r t u b e l e v e l i n d i c a t o r w a s r e l i a b l e and appeared t o be reasonably a c c u r a t e , although s e r i o u s plugging

w a s noted a t t h e f i n a l i n s p e c t i o n .

F u r t h e r s t u d y should i n d i c a t e whether

t h e plugging prDblem caT= be moderated ky d e s i g n o r o p e r a t i o n a l changes. A t worst, we should be alsle t o accommodate t u b e replacement on a two-year cycle. I n June 1968, i n response t o a s u g g e s t i o n by J. W. Krewson, ORNL I n s t r u m e n t a t i o n and Control D i v i s i o n , a b r i e f t e s t w a s made u s i n g a r e s i s t a n c e probe f o r i n d i c a t i n g s a l t l e v e l i n t h e pump bowl.

The i n p u t

s i g n a l w a s 1000 Hz a t low v o l t a g e , and t h e output s i g n a l w a s a s t r a i g h t l i n e f u n c t i o n of s a l t l e v e l over t h e lower t h i r d o f t h e probe.

Calibration

t o a depth of 2 i n . produced a reasonably s t r a i g h t l i n e w i t h a s l o p e of

75 mV/in.

The t e s t w a s t e r m i n a t e d a f t e r one week due t o c a t a s t r o p h i c c o r -

r o s i o n of t h e s t a i n l e s s s t e e l probe by t h e f l u o r o b o r a t e environment. Subsequently, c o r r o s i o n t e s t s were r u n u s i n g probes made from H a s t e l l o y N

material, and t h e r e s u l t s i n d i c a t e d t h a t t h e s e v e r e c o r r o s i o n of t h e

95 W

s t a i n l e s s s t e e l probe w a s normal f o r o p e r a t i o n i n f l u o r o b o r a t e s a l t a t

lO25"F, t h a t a c c e p t a b l e c o r r o s i o n rates could be achieved by u s i n g a n a p p r o p r i a t e material such as H a s t e l l o y N, and t h a t t h e use of a highfrequency e l e c t r i c a l c u r r e n t d i d n o t appear t o c o n t r i b u t e t o t h e c o r r o sion.

W e d i d n o t have an o p p o r t u n i t y t o r e p e a t t h e salt l e v e l c a l i b r a t i o n

using t h e H a s t e l l o y N probe.

6.7

Back D i f f u s i o n a t t h e Pump S h a f t

The purge gas t h a t e n t e r e d t h e pump s h a f t annulus w a s s p l i t i n t o two streams; t h e l a r g e r stream flowed down t h e s h a f t and i n t o t h e pump bowl vapor space, and t h e o t h e r stream, 100 c$/min

o r about 11% of t h e

t o t a l flow, flowed up t h e s h a f t , p a s t t h e s h a f t s e a l , through t h e o i l c a t c h t a n k , and f i n a l l y w a s vented i n t o t h e l o o p e n c l o s u r e .

The end of

t h i s v e n t l i n e , a 1 / 4 - i n . t u b e , would g r a d u a l l y plug over a p e r i o d of s e v e r a l months of o p e r a t i o n , i n d i c a t i n g t h a t t h e gas c o n t a i n e d some BF3. The composition of t h e plug material w a s not determined. S e v e r a l t e s t s were made i n which t h e s e a l purge stream w a s passed through t h e t h e r m a l c o n d u c t i v i t y c e l l when t h e s h a f t purge w a s a t t h e normal s e t t i n g of 850 c$/min

and t h e s a l t temperature w a s a t 1025째F.

I n none of t h e t e s t s w a s t h e r e any d i s c e r n i b l e change i n s i g n a l when compared w i t h pure helium sample g a s . c a l i b r a t i o n s l o p e of

The thermal c o n d u c t i v i t y c e l l had a

4.7% BF3 p e r mV, and t h e smallest c h a r t change t h a t

could be d e t e c t e d w i t h confidence w a s 0.02 mV, which would be e q u i v a l e n t t o 0.1% o r 1000 ppm.

It w a s concluded from t h i s t h a t t h e BF3 c o n t e n t of

t h e seal purge stream w a s less t h a n 1000 ppm and t h a t t h e c o n c e n t r a t i o n r a t i o between t h e purge stream and t h e pump bowl g a s w a s n o t more t h a n

0 .O3 (0.1%/3.5%) r u n on t h i s pun$

This r e s u l t i s i n agreement w i t h b a c k - d i f f u s i o n t e s t s

using 8 5 K r ,

where a c o n c e n t r a t i o n r a t i o of 0.01 w a s

observed for t h e same purge flow.

I n a n o t h e r t e s t , w i t h t h e system a t

s t e a d y state, we reduced t h e s h a f t purge rate by a f a c t o r of 2 and d i d not g e t any response from t h e thermal c o n d u c t i v i t y c e l l . Ref.

8 i n d i c a t e t h a t a f a c t o r of 2 i n t o t a l purge would change t h e con-

c e n t r a t i o n r a t i o by an o r d e r of magnitude. W

Data from

From t h i s we might i n f e r t h a t

96 a t t h e normal s h a f t purge rate of 950 c+/min t h e BF3 c o n t e n t of t h e lower purge stream could have been as low as 100 ppm.

6.8 A S a l t Leak t o t h e AtmosDhere On t h e morning of September 2 3 ,

1969, a f t e r 8700

t h e fluorohorate s a l t , a salt l e a k w a s discovered.

h r of o p e r a t i o n w i t h

The i n i t i a l i n d i c a t i o n s

of t r o u b l e were a decrease i n pump bowl l i q u i d l e v e l of

8% (-0.8

i n . salt),

an apparent decrease i n t h e temperature of c i r c u l a t i n g s a l t , and i r r e g u l a r temperatures a t t h e two v e n t u r i p r e s s u r e t r a n s m i t t e r s .

A v i s u a l inspection

i n s i d e t h e l o o p e n c l o s u r e r e v e a l e d a s t a l a c t i t e of f r o z e n s a l t hanging from t h e i n s u l a t i o n surrounding b o t h v e n t u r i p r e s s u r e t r a n s m i t t e r s and a s m a l l q u a n t i t y of s a l t i n t h e floor pan beneath them.

Using normal shutdown pro-

cedures, t h e pump w a s stopped and t h e s a l t w a s d r a i n e d i n t o t h e sump t a n k . The l e a k w a s found t o 3e at t h e v e n t u r i i n l e t p r e s s u r e t r a n s m i t t e r (FT

104A) i n t h e weld t h a t j o i n s a 1 / 2 - i n . - I P S p i p e t o t h e b o s s on t h e d i a phragm f l a n g e ( F i g . 35).

This i s a s t a g n a n t s a l t zone s e r v i n g only t o

sense v e n t u r i i n l e t p r e s s u r e , which i s about 100 p s i g w i t h t h e pump on. The d e f e c t i v e p r e s s u r e t r a n s m i t t e r w a s removed from t h e system, t h e pipe nozzle t o which it had been a t t a c h e d w a s capped o f f , and o p e r a t i o n of t h e l o o p w z s resumed. M e t a l l u r g i c a l examination of t h e p r e s s u r e t r a n s m i t t e r i n d i c a t e d t h a t t h e weld (made i n

1956) P a d

been d e f e c t i v e when made by t h e vendor, and

t h a t t h e d e f e c t had been r e p a i r e d by applying b r a z e metal t o t h e i n t e r i o r surface.

It i s e s t i m a t e d t h a t t h e p r e s s u r e t r a n s m i t t e r had been i n s e r v i c e

i n t h e l o o p f o r a t least e i g h t y e a r s and, p r i o r t o t h e c u r r e n t f l u o r o b o r a t e s e r v i c e , w a s o p e r a t e d f o r t h r e e y e a r s w i t h a s a l t similar t o t h e MSRE f u e l

salt. The conclusions r e s u l t i n g from t h e i n v e s t i g a t i o n of t h e l e a k were as follows :

1. The s a l t l e a k w a s a t t r i b u t e d t o t h e failure of a welded c l o s u r e t h a t w a s d e f e c t i v e when o r i g i n a l l y made and which had been r e p a i r e d by a technique, which based on c u r r e n t technology, could not be recommended f o r m o l t e n - s a l t s e r v i c e a t 1000째F. NaBF,

service was coincidental.

The f a c t t h a t t h e l e a k occurred during

ORNL DWG 7 2 - 2 0 9 5

Fig. 35.

(PT

L o c a t i o n o f leak on v e n t u r i i n l e t p r e s s u r e t r a n s m i t t e r

104A), N a i 3 F 4 c i r c u l a t i o n t e s t , PKF’ l o o p .

98 2.

Corrosion i n t h e stagnarit l e g between t h e p r e s s u r e t r a n s m i t t e r

and t h e l o o p w a s r e l a t i v e l y mild and w a s similar t o t h a t experienced w i t h Inconel i n o t h e r NaBF4 l o o p s .

The consequences of t h e l e a k can be c h a r a c t e r i z e d as r a t h e r m i l d .

If t h e r e were any v i s i b l e fumes, t h e y were c a r r i e d o f f t o t h e s t a c k by t h e

c o n t r o l l e d v e n t i l a t i o n system. e n e r g j release.

There w a s no i n d i c a t i o n of f i r e or sudden

The c o n d i t i o n of t h e containment system metal i n t h e

v i c i n i t y of t h e h o l e seemed t o i n d i c a t e t h a t t h e l e a k w a s not s e l f aggravating, t h a t i s , continued leakage d i d not r e s u l t i n an i n c r e a s e i n t n e rate of l e a k a g e .

6.9 Experience w i t h Handling BF, P r o p e r t i e s of BF3 and s u g g e s t i o n s f o r handling and s t o r a g e have been e x c e r p t e d from manufacturers' l i t e r a t u r e and i n c l u d e d i n Appendix A.

g e n e r a l , our experience during t h e t e s t program w a s i n agreement w i t h t h e l i t e r a t u r e , and t h e following comments are i n c l u d e d f o r emphasis or t o p r e s e n t o b s e r v a t i o n s wlzich should b e of s p e c i a l i n t e r e s t . 1. There was no evidence of c o r r o s i v e a t t a c k i n t u b i n g , p i p e , and v e s s e l s where t h e gas w a s d r y , t h a t i s , excluded from c o n t a c t w i t h moist

air.

Converselj;, where t h e r e w a s o p p o r t u n i t y f o r c o n t a c t w i t h moist a i r ,

t h e r e s u l t i n g comk'ination w a s extremelji c o r r o s i v e .

Handling problems

w i l l be minimized i f e x t r a p r e c a u t i o n s are t a k e n t o i n s u r e a dry, l e a k t i g h t system lciefore a d m i t t i n g 3F3. 2.

A flow r e s t r i c t i o n developed p e r i o d i c a l l y a t t h e p o i n t where

t h e o f f - g a s stream ( 3 1/2$ BF3 i n helium) w a s vented i n t o t h e s t a c k s u c t i o n l i n e (see S e c t . 5 . 4 ) .

I n September

1967, seventeen

1800-psig c y l i n d e r s of BF3 (nominally

60 l bm p e r c y l i n d e r ) were purchased t o provide f o r expected usage d u r i n g t h e t e s t program.

The use rate w a s lower t h a n o r i g i n a l l y p r e d i c t e d , s o

t h a t most of t h e c y l i n d e r s were s t i l l on hand by t h e summer of 1968. May, June, and J u l y t h e atmosphere.

1968, f i v e of t h e s t o r e d c y l i n d e r s developed l e a k s t o

One of t h e l e a k s w a s due t o d e f e c t i v e packing, b u t t h e

o t h e r l e a k s r e s u l t e d from t h e f a c t t h a t t h e c y l i n d e r v a l v e s were equipped w i t h improperly rated s a f e t y d e v i c e s .

The l e a k y c y l i n d e r s were

v e n t e d t o t h e atmosphere a t a remote l o c a t i o n , and e i g h t of t h e remaining c y l i n d e r s w e r e r e t u r n e d t o t h e vendor.

J u s t b e f o r e v e n t i n g t o t h e s t a c k s u c t i o n , t h e off-gas stream w a s

passed through a m i n e r a l - o i l t r a p t o i n h i k i t back d i f f u s i o n of moist a i r . There w e r e no v i s u a l ill e f f e c t s on t h e m i n e r a l o i l during t h e t e s t p e r i o d . The e f f e c t i v e n e s s of t h i s device i n p r e v e n t i n g back d i f f u s i o n of moisture

w a s n o t measured q u a n t i t a t i v e l y , b u t two o b s e r v a t i o n s i n d i c a t e d t h a t it was satisfactory.

F i r s t , t h e r e were no accumulations of moisture i n t h e

mineral o i l bubbler tank.

Second, t h e r e w a s no evidence o f c o r r o s i v e

a t t a c k i n t h e t u b i n g on t h e upstream side o f t h e b u b b l e r , i n d i c a t i n g t h e absence of s i g n i f i c a n t moisture l e v e l s .

6.10 Corrosion Ekperience The development and e v a l u a t i o n of c o n t a i n e r materials f o r i'luorob o r a t e s e r v i c e i s b e i n g done by o t h e r s i n o t h e r t e s t equipment.'

How-

e v e r , t h e r e were c e r t a i n p i e c e s of hardware i n s t a l l e d new i n t h e f l u o r o b o r a t e system t h a t w e r e exposed t o s e r v i c e c o n d i t i o n s o f i n t e r e s t .

b r i e f h i s t o r y and g e n e r a l d e s c r i p t i o n are p r e s e n t e d below. The pump tank s a l t l e v e l bubbler tube i n s t a l l a t i o n i s d e s c r i b e d i n S e c t i o n 6.6.

The t u b e , which w a s made from a 5 / 8 - i n . - 0 ~ , O.O65-in.-wall

Inconel t u b e , w a s i n s t a l l e d b e f o r e t h e l o o p s t a r t u p , and it w a s removed on October 23, 1970. Fig.

36.

The p o s t - t e s t e x t e r i o r appearance i s shown i n

The tube w a s c u t i n t o f o u r pieces by making t r a n s v e r s e c u t s a t

7 1/2 i n . from t h e lower end. The t h r e e lower p i e c e s w e r e t h e n s l i t a x i a l l y . Figure 37 shows t h e i n t e r i o r appearance of t h e t u b e . 1, 4 1/2, and

The b u b b l e r tube w a s examined chemically and m e t a l l u r g i c a l l y , and t h e r e -

sults are p r e s e n t e d i n R e f s . 10 and 11. The p r e s s u r e c o n t r o l v a l v e w a s used throughout t h e t e s t program. The v a l v e o p e r a t e d a t room temperature and absorbed t h e f u l l p r e s s u r e drop of

24 p s i .

It had t o be opened and cleaned a number of times t o

remove accumulations of s a l t and l i q u i d i m p u r i t i e s .

The s t a i n l e s s s t e e l

v a l v e t r i m ( F i g . 38) appeared t o be e s s e n t i a l l y f r e e of c o r r o s i v e a t t a c k when examined v i s u a l l y on October 26,

1970.

100

- -.

LJ *

Fig. 36.

Post-test appearance of salt level bubbler tube exterior.

101

Fig. 37.

Post-test appearance of s a l t l e v e l bubbler tube i n t e r i o r .

Fig. 38.

Post-test appeazance of pressure control valve t r i m .

During t h e f i n a l examination of t h e pump r o t a r y element, p i e c e s of gray-black, magnetic, m e t a l l i c - a p p e a r i n g material, shaped somewhat l i k e automobile t i r e weights, were found l y i n g i n t h e annulus next t o t h e i m p e l l e r hub.

The chemical a n a l y s i s [ N a - 5 ,

B-3, Fe-2.5, Cr-0.2, and ~ i - 6 6 . 3

( w t % ) ] i n d i c a t e d t h a t t h e material w a s elemental n i c k e l mixed w i t h some

NaBF4.

We s p e c u l a t e t h a t t h e material w a s formed n e a r t h e upper end of

t h e i m p e l l e r hub by mass t r a n s f e r of n i c k e l from t h e s a l t t h a t flowed through t h e i m p e l l e r - s h a f t l a b y r i n t h seal ( f o u n t a i n flow) .

Evidence of

severe c o r r o s i o n w a s found on t h e i n n e r h e a t b a f f l e s , 1 2 and t h i s c o n d i t i o n w a s a s c r i b e d t o continuous low l e v e l s of moisture ( e s t i m a t e d t o be about

25 ppm) i n t h e s h a f t purge helium g a s . been as f o l l o w s :

The mechanism i s b e l i e v e d t o have

r e s i d u a l d r o p l e t s of f l u o r o b o r a t e s a l t were l e f t on t h e

h e a t b a f f l e s u r f a c e s as a result of t h e i n g a s s i n g t r a n s i e n t s which occurred during t h e c a v i t a t i o n i n c e p t i o n t e s t s and t h e moisture i n t h e incoming purge gas combined w i t h t h e s e s a l t d r o p l e t s t o form c o r r o s i v e r e a c t i o n products.

6.11 Green S a l t When t h e pump r o t a r y element w a s removed f o r i n s p e c t i o n i n May

1968,

s e v e r a l l a r g e chunks of green s a l t were found l y i n g on t o p of t h e upper impeller casing.

It w a s concluded t h a t t h i s material w a s a r e l a t i v e l y

i n s o l u b l e phase t h a t r e s u l t e d from mixing t h e f l u o r o b o r a t e f l u s h i n g s a l t with t h e r e s i d u e of MSRE-type s a l t l e f t over from t h e previous t e s t program.

The c o l o r w a s similar t o , b u t not q u i t e as d a r k as, t h e green de-

p o s i t s (N+ CrFG) o b t a i n e d d u r i n g t h e c o l d - f i n g e r t e s t work.

1970, when

I n September

t h e r o t a r y element w a s a g a i n removed from t h e pump, a similar

d e p o s i t of green salt w a s found on t h e upper i m p e l l e r c a s i n g .

I n both

c a s e s , it w a s obvious t h a t t h e d e p o s i t s had been formed on t h e under s i d e of t h e o u t e r t h e r m a l baffles and had been d i s l o d g e d d u r i n g removal of t h e r o t a r y element.

This t h e r m a l b a f f l e s u r f a c e w a s probably somewhat c o l d e r

t h a n t h e b u l k s a l t temperature, which would account f o r p r e c i p i t a t i o n of t h e l e s s - s o l u b l e phase; b u t t h e s u r f a c e w a s about

4 in.

above t h e maximum

normal pump bowl s a l t l e v e l , and it i s not c l e a r how t h e s a l t came i n t o contact with t h i s surface.

There are two p o s s i b i l i t i e s :

first, splashing

or spraying of t h e s a l t due t o i m p e l l e r f o u n t a i n flow, and second, t h e

v i o l e n t b u t momentary expansions of t h e s a l t t h a t occurred d u r i n g t h e i n g a s s i n g t r a n s i e n t s (see S e c t .

6.1).

The f i r s t mechanism seems more

probable, s i n c e t h e i n g a s s i n g t r a n s i e n t s were s o b r i e f t h a t it i s d i f f i c u l t t o see how t h e r e could have been s u f f i c i e n t c o n t a c t t i m e t o a l l o w t r a n s f e r of t h e material.

after only

187 h r

On t h e o t h e r hand, t h e f i r s t d e p o s i t w a s found

of s a l t c i r c u l a t i o n , which i m p l i e s a r a t h e r r a p i d t r a n s -

f e r rate even f o r t h e s p r a y t h e o r y .

Table 11 compares t h e chemical analy-

ses of t h e green s a l t s w i t h t h e v a r i o u s charges of c i r c u l a t i n g s a l t , and Table 12 compares molecular compositions of t h e c i r c u l a t i n g salts w i t h p o s s i b l e molecular compositions f o r t h e green s a l t s . The discovery of t h e d e p o s i t s of green salt s u g g e s t s t h e p o s s i b i l i t y of similar d e p o s i t s i n a n MSBR secondary c o o l a n t system i f t h e r e were leakage of t h e f u e l s a l t i n t o t h e coolant s a l t .

The p o s s i b l e r a m i f i c a t i o n s

of such an i n c i d e n t need t o be thoroughly considered t o i n s u r e that t h e r e would 5e no i n t o l e r a b l e s i d e e f f e c t s .

Takle 11. Comparison of green s a l t w i t h p r e s e n t and former s a l t s f o r NaBF4 c i r c u l a t i o n t e s t , PKP-1 l o o p

BULT-4 s a l t

NaBF,

s a l t ( w t $)

formerly i n l o o p (wt

Flush charge"

Clean b a t c h

0.21

9e72 5.82

0.17

0.048 0.016

5.12

0.25

0.019

0.25

20.o

May

4) Sept .

1968

1970

Green s a l t ( w t

0.21

0.17

0.04

0.10

12.2

0.02

0.093 20.9 9.3 68.0 0.06

0.01

0.04

26.5 10.9 3 -9143.5 1.48 0.27

0.04

0.005

0.03

21.6

9.45 67.7

59.34

0.35 13.9 17.8 2.6 45.3 9.45 8.9 0.08

a After mixing w i t h h e e l of s a l t l e f t i n d r a i n t a n k from previous t e s t program.

Table 12.

a Comparison of molecular compositions of c i r c u l a t i n g salts and green s a l t s -

Fluoroborate s a l t

BULT-4 s a l t formerly i n l o o p

Flush charge

88 6

NaBFB NaF

Clean charge

93 5

LiF

0.1

BeF2

0.2

Green s a l t May

Sept.

1968

1970

53 13 4

32 8

0.7 7

3 2

UF4

0.1

0.01

mF4 N@ CrF6

0.1

0.04

0.02

0.08

0.7 23

0.04

0.1

FeF2 a

I n f e r r e d from chemical a n a l y s e s ; a l l v a l u e s i n mole

6.12

0.2

9 23

Valves i n BF? S e r v i c e

I n g e n e r a l , t h e performance of i n - l i n e v a l v e s , whether packed stem

seal o r bellows stem seal, w a s very s a t i s f a c t o r y .

We a t t r i b u t e s u c c e s s

i n t h i s area t o t h e use of r e s i s t a n t materials ( f l u o r i n a t e d polymers) f o r g a s k e t s and packing and t o c a r e i n l e a k t e s t i n g t o i n s u r e a t i g h t I n a f e w instances a valve stuck i n t h e closed position.

system.

This

d i f f i c u l t y w a s a t t r i b u t e d t o accumulation of f l u i d or s o l i d s and t o t h e f a c t t h a t t h e v a l v e s opened on s p r i n g a c t i o n , t h a t i s , t h e stems were not d i r e c t l y connected t o t h e v a l v e wheel. I n c a s e s where a v a l v e w a s used t o s e p a r a t e t h e BF3 system from t h e atmosphere, t h e experience w a s n o t s o good.

One example w a s t h e 1 - i n .

b a l l v a l v e t h a t w a s i n s t a l l e d on t h e s a l t sample a c c e s s l i n e on t h e pump bowl.

!This v a l v e had a s t a i n l e s s steel body and Teflon t r i m , b u t we had

c o n t i n u a l t r o u b l e w i t h seat l e a k a g e .

We attributed the trouble t o attack

by c o r r o s i v e materials produced by t h e r e a c t i o n of BF3 with atmospheric W

moisture.

Another example w a s t h e s a f e t y r e l i e f v a l v e t h a t w a s i n a l i n e

connected t o t h e BF,

feed h e a d e r .

This v a l v e had a s p r i n g - l o a d e d brass

poppet and a s y n t h e t i c - r u b b e r elastomer (Buna N ) seat.

A check a f t e r

t h e f i n a l shutdown of t h e l o o p showed t h a t t h e poppet opened a t about t h e r i g h t cracking p r e s s u r e b u t f a i l e d t o reseat when t h e p r e s s u r e w a s lowered.

We b e l i e v e t h e failure t o reseat w a s due t o BF3-H,0 r e a c t i o n

products which caused a change i n t h e p r o p e r t i e s of t h e e l a s t o m e r .

t h i r d example w a s t h e check v a l v e i n t h e o f f - g a s l i n e j u s t b e f o r e t h e stack suction.

The o r i g i n a l v a l v e , which had a s p r i n g - l o a d e d b r a s s

poppet w i t h a Buna N s e a t , s t u c k c l o s e d a f t e r

766 h r of o p e r a t i o n .

ure w a s a t t r i b u t e d t o d e t e r i o r a t i o n of t h e e l a s t o m e r s e a t .

Fail-

We changed

t h e rubber r i n g t o a Poly-TFE r i n g and had no f u r t h e r d i f f i c u l t y . I n s-xy,

t h e v a l v e a p p l i c a t i o n s t h a t :?quire

c l o s e a t t e l l t i o n are

i n l o c a t i o n s where t h e r e i s an o p p o r t u n i t y f o r t h e BF, t o come i n t o cont a c t w i t h atmospheric m o i s t u r e .

Good performance can be o b t a i n e d by t h e

use of well-designed v a l v e s having proper materials of c o n s t r u c t i o n .

For i n f r e q u e n t l y used l i n e s , it may be a d v i s a b l e t o provide for purging and capping o f f t h e l i n e on t h e atmospheric side of t h e v a l v e .

RECOJDENDATIONS FOR FLâ&#x20AC;&#x2122;RTHER DEVELOPMENT WORK

7.1

Impurities i n t h e S a l t

C e r t a i n i m p u r i t i e s , v a r i o u s l j i d e n t i f i e d as w a t e r , hydroxyfluoroboric a c i d , BF,

-H, 0 r e a c t i o n p r o d u c t s , e t c ., cause i n c r e a s e d c o r r o s i o n ratesâ&#x20AC;&#x2122;

i n t h e c i r c u l a t i o n system and flow r e s t r i c t i o n s i n t h e o f f - g a s system. Work i s needed i n t h e following a r e a s :

(1) i d e n t i t y and p e r t i n e n t physi-

c a l p r o p e r t i e s ( e . g . , vapor p r e s s u r e ) of t h e i m p u r i t i e s , ( 2 ) m a x i m u m c o n c e n t r a t i o n of t h e i m p u r i t i e s which can be t o l e r a t e d i n t h e s a l t , and

( 3 ) procedure f o r p r e t r e a t i n g s a l t t o remove i m p u r i t i e s . 7.2

Corrosion Product Deposition

A d d i t i o n a l work i s needed t o v e r i f y t h e s u i t a b i l i t y of a c o l d t r a p ping t e c h n i q u e t o i n h i b i t t h e d e p o s i t i o n of c o r r o s i o n products on steam g e n e r a t o r t u b e s and o t h e r f u n c t i o n a l s u r f a c e s where f o u l i n g i s unwanted.

7 . 3 S a l t Level Instruments We need a r e l i a b l e , a c c u r a t e method f o r continuous i n d i c a t i o n of salt l e v e l .

Two d e v i c e s were t e s t e d .

The t e s t of t h e r e s i s t i v i t y probe

w a s c u r s o r y , and a d d i t i o n a l work i s needed t o provide a r e l i a b l e e v a l u a t e o n of i t .

A d d i t i o n a l work i s needed w i t h t h e bubble-tube i n d i c a t o r

t o i n s u r e t h a t we have a s u i t a b l e c o n s t r u c t i o n material and t o develop

a design t h a t w i l l n o t be s u s c e p t i b l e t o plugging.

The accuracy and

s t a b i l i t y of b o t h t y p e s need t o b e e s t a b l i s h e d .

7.4 O f f - G a s System R e s t r i c t i o n s We have proposed t h e use of a hot-mist t r a p and a r e p l a c e a b l e f i l t e r t o h e l p e l i m i n a t e flow r e s t r i c t i o n s i n t h e o f f - g a s system.

The word

" r e p l a c e a b l e " i m p l i e s a p a r a l l e l f i l t e r i n s t a l l a t i o n with p r o v i s i o n s f o r i s o l a t i n g and s e r v i c i n g t h e o f f - s t r e a m u n i t .

The problem i s t o d e s i g n

an arrangement t h a t does n o t t e n d t o plug a t t h e i s o l a t i o n v a l v e between t h e hot-mist t r a p and t h e f i l t e r .

Our t e s t work showed t h a t globe v a l v e s

would b e u n s u i t e d f o r t h i s a p p l i c a t i o n .

B a l l v a l v e s , which have a

s t r a i g h t - t h r o u g h flow p a t t e r n , might be s a t i s f a c t o r y from t h e s t a n d p o i n t of s o l i d s accumulation, b u t t h e i r packed-stem s e a l d e s i g n might b e unacceptable f o r a nuclear r e a c t o r i n s t a l l a t i o n .

One p o s s i b l e approach

would be t o dodge t h e problem a l t o g e t h e r by e l i m i n a t i n g t h e i s o l a t i o n v a l v e s and s i z i n g t h e f i l t e r s o t h a t replacement would be n e c e s s a r y o n l y d u r i n g scheduled r e a c t o r shutdowns.

We need t o examine t h e v a r i o u s

a l t e r n a t i v e s and t o d e f i n e and perform t e s t s t h a t w i l l demonstrate t h a t

we have a s a t i s f a c t o r y s o l u t i o n t o t h i s problem.

7.5

Control of S a l t Composition

I n connection w i t h t h e use of t h e t h e r m a l c o n d u c t i v i t y c e l l t o monit o r t h e composition of t h e s a l t two t e s t s are needed:

(1) t h e instrument

should be used t o check a s a l t t h a t i s known t o be n o n e u t e c t i c , and ( 2 )

t e s t s should be r u n t o determine t h e v a r i a t i o n of BF, p a r t i a l p r e s s u r e as a f u n c t i o n of t h e q u a n t i t y of f u e l s a l t t h a t i s mixed with t h e f l u o r o borate.

108

7.6

Intermixing of Molten S a l t s

Additional s t u d y i s needed t o examine t h e r e l a t i v e m i s c i b i l i t y of v a r i o u s mixtures of t h e f l u o r o b o r a t e s a l t w i t h t h e r e a c t o r f u e l s a l t . The purpose i s t o i n s u r e t h a t c r o s s mixing of s a l t between t h e f u e l and coolant systems would not cause any i n s o l u b l e s a f e t y o r o p e r a t i n g prob-

lems.

This study can probably be c a r r i e d out i n c o n j u n c t i o n w i t h t h e

work noted i n S e c t i o n 7.5 above.

7.7 S o l i d Phase T r a n s i t i o n S t u d i e s should be made t o determine i f s p e c i a l designs or o p e r a t i n g techniques are needed t o prevent damaging stresses when s a l t - f i l l e d components are h e a t e d upward through t h e s o l i d phase t r a n s i t i o n temperature

(469째F). A b r i e f , simple t e s t w a s r u n ( s e e Appendix E ) t h a t i n d i c a t e s t h a t proper adjustment of h e a t e r temperatures i s probably an important factor.

A d d i t i o n a l s t u d y i s needed, however, t o i n s u r e t h a t w e can cope

w i t h t h i s prok,lem i n complex c i r c u l a t i n g systems. The s o l i d phase t r a n s i t i o n might a l s o be expected t o cause problems with t h e o p e r a t i o n of freeze v a l v e s , although t h i s h y p o t h e s i s w a s not supported by o w experience (see S e c t .

6.4) d u r i n g

t h e t e s t program.

lie

recommend a c r i t i c a l review of t h e design and o p e r a t i o n of f l u o r o b o r a t e f r e e z e v a l v e s followed k ; ~t h e executior, of any experimental work t h a t might be i c d i c a t e d by t h i s review.

7.8 EF3 Recycle System The 3F3 usage r a t e i s d i r e c t l y p r o p o r t i o n a l t o t h e BFs p a r t i a l p r e s -

sure.

I n t h e MSBR concept, t h e BF,

p a r t i a l pressure w i l l be r e l a t i v e l y

h i g h (about o n e - t h i r d of an atmosphere) and t h e usage rate f o r a oncethrough BF3 f e e d system would b e on t h e o r d e r of 100 f t 3 / d a y o r 20 lbm/day ( b a s e d on a t o t a l p r e s s u r e of 2 ztm and t o t a l flow of 12 l i t e r s / m i n ) . The problem of BF, supply and d i s p o s a l would be minimized i f a system

were provided t o r e c y c l e a l a r g e f r a c t i o n of t h e BF,, and a s t u d y should b e made t o examine t h e f e a s i b ' i l i t y and d e s i r a b i l i t y of such a r e c y c l e system.

ACKNOWLEDGMENTS

The work d e s c r i b e d h e r e i n r e q u i r e d and r e c e i v e d c o n s t r u c t i v e i n p u t s from many persons.

!The major c o n t r i b u t o r s are l i s t e d below.

Dunlap S c o t t , guidance i n formulation of t e s t program; R. B . G a l l a h e r , P. G . Smith, and H . C . Young, e x e c u t i o n and a n a l y s i s of tests; W. H . Duck-

worth, F. E. Lynch, and Doyle S c o t t , o p e r a t i o n of t e s t equipment; Ben S q u i r e s , d e s i g n of c o n t r o l system; C. A . Brandon, d e s i g n of c o l d f i n g e r ; R . F. Apple, S . Cantor, A. S . Meyer, Jr., and J. A. S h a f f e r , chemistry

support; Dunlap S c o t t , A . G . G r i n d e l l , R . E. MacPherson, and R . B. Briggs, c o n s t r u c t i v e review of r e p o r t drafts.

W e are a l s o i n d e b t e d t o V . B. Maggart for t y p i n g of t h e r e p o r t and t o M. R . Sheldon f o r a s s i s t a n c e w i t h t h e f i n a l e d i t i n g .

are hereby g r a t e f u l l y acknowledged.

A l l contributions

REFERENCES

1. R. C . Robertson e t a l . , Two-Fluid Molten-Salt Breeder Reactor Design Study ( S t a t u s as of January 1, 1968), ORNL-4528, pp. 9-11. (August 1970) 2.

Reactor Handbook, v o l .

IT,2d e d . , p . 832, I n t e r s c i e n c e , New York,

1964 *

P. G. Smith, "Hydraulic Performance and C a v i t a t i o n I n c e p t i o n Charact e r i s t i c s with Fluoroborate - PKP S a l t Pwnp (MSR-69-3), 'I unpublished i n t e r n a l memorandum ( J a n . 10, 1969).

A . N. Smith e t a l . , MSRP Semiannu. Progr. Rep. February 1969, ORNL4396, p . 100.

S . Cantor e t a l . , P h y s i c a l P r o p e r t i e s of Molten-Salt Reactor Fuel, Coolant, and Flush S a l t s , ORNL-TM-2316, pp. 33-35 (August 1968).

S Cantor, MSRP Semiannu. Progr pp. 159-61.

. Rep.

August

1967, ORNL-4191,

7. NSRP Semiannu. Progr. Rep. February 1969, ORNL-4396, p . 105. 8.

"Rotating Machinery f o r Gas-Cooled Reactor A p p l i c a t i o n , 'I Proceedings of Meeting at Oak Ridge National Laboratory, A p r i l 2-4, 1962,

TID-7631.

9. 10.

J. W. Koger and A. P. Litman, C o m p a t i b i l i t y of Fused Sodium Fluorob o r a t e s and BF3 G a s with H a s t e l l o y N Alloys, Om-TM-2978 ( J u n e 1 9 7 0 ) . S . Cantor, MSRP Semiannu. Progr. Rep. Feb.

1971, Om-4676, pp. 9 2 9 3 .

11. J. W. Koger, i b i d . , pp. 211 f f .

12.

MSRP Semiannu. Progr. Rep. Aug. 31,

1-3*

J. W. Koger, MSRF Semiannu Progr pp. 168-69.

1971, ORNL-4728, pp. 31

. Rep.

August

ff.

1971, ORNL-4622,

B I E L I CGRAPHY

1. H . S. Booth and D. R. Martin, Boron T r i f l u o r i d e and I t s D e r i v a t i v e s , Wiley, New York, 1949. 2.

Matheson Gas Data Book, The Matheson Co., I n c . , E a s t Rutherford, N . J . , 1961.

111

APPENDICES

Appendix A

SEUCTED PHYSICAL AND CHEMICAL PROPERTIES OF PROCESS MATERIALS

A.l

NaBF,

and NaF

Name

Sodium f l u o r o b o r a t e

Sodium f l u o r i d e

Formula

NaBF,

NaF

Molecular weight

109.8

2.47

765

2.79 1818

A t 25"c

108

A t 100 "C

210

Density, g/cm',

20째C

Melting p o i n t , "F S o l u b i l i t y , g/100 g %O

A.2

The System NaE3Fd-NaF Phase diagram BF,

dec ompos it ion

See F i g . A . l See F i g . A . 2

pressure Mole f r a c t i o n NaBF4

( 2 .126 )

(w) o

(O.569R - 3 ) A. 3

sodium

, where

R =

Na -

B -

-F

0.92 9.95 9.53

3.76 71.44 68.44

NaBF, -NaF E u t e c t i c Com-oositi o n N&F,-NaF

NaBF,

NaF -

Moles

0.92

0.08

Grams

104.39

101.3 96.77

3.36 3.22

Weight

100

22.02

Pro-oerties (Note: The following p r o p e r t i e s are f o r t h e l i q u i d unless o t h e r w i s e indicated. ) Conductivity 1

E l e c t r i c a l , (0-cm)' 1

Thermal, Btu h r -

u =

2.7 + 7.2 x 10- (T OF - 932)

0.3

f t - ' ( OF)-

Density 4

g/c*

p =

2.27 - 4.1 x 10- T OF

lbm/ft3

p =

142.5 - 2.56 X 10- T OF

1025"F (551.7"~)

p =

1.86 g/C$

116 l bm/ f t 3

1150"~ (621.1"~)

p =

1.81 g/C$

1-13 l b m / f t 3

S o l i d phase t r a n s i t i o n a t

Density of s o l i d , g/cn?

469.4"F

(243째C) <469"F:

p =

2.52

- 6.67 X

10- T 5

2469"~:p

2.15 - 6.67 x io(T OF - 469.4)

Expansion 1

Thermal, ( OF)-

cy =

1.1 x 10-

Solid

6.7 x 10-

Heat c a p a c i t y 1

B t u lbm- (OF)-

Solid,

77 - 469째F

0.36 4

C = 0.22 P

469 - 718째F

C P

0.34

55.8

AH =

26.1

Heat of f u s i o n Btu/lbm Solid t r a n s i t i o n , Melting p o i n t , OF

469.4"F

723

+ 3.2 x 10- T OF

O F

S o l u b i l i t y of i n e r t g a s e s , 10- lbi/mole of gas p e r f t 3 melt p e r a t m

Kr XE!

S u r f a c e t e n s i o n , dynes/cm

- 4.7 - 9.2 - 8.5

121.3 - 0.0417T "F

Decomposition p r e s s u r e

See F i g . A . 2

V i s c o s i t y , CP

7 = 0.04

exp(T 5400

1025"F

7 = 1.52

Name

Boron t r i f l u o r i d e ( a l s o boron fluoride )

Formula

BF3

Molecular weight

67.82

S p e c i f i c volume, f t 3 / l b m

5.6 -148.5 -196.8

Boiling point, Freezing p o i n t ,

S p e c i f i c g r a v i t y , 5 0 " ~( a i r C r i t i c a l temperature,

Btu l b - I mole-

-D e s c r i p t i o n .

2.37 10

C r i t i c a l pressure, p s i a S p e c i f i c h e a t of gas a t

732

44"F,

( OF)-'

Boron t r i f l u o r i d e i s a c o l o r l e s s gas t h a t fumes i n

moist a i r and h a s a pungent, s u f f o c a t i n g odor. does n o t support combustion.

It i s nonflammable and

It i s normally packaged i n c y l i n d e r s as

a n o n l i q u e f i e d gas a t a p r e s s u r e of 2000 p s i g at

7 0 " ~ .It

i s very s o l u -

b l e i n water w i t h decomposition (forming f l u o r o b o r i c and b o r i c a c i d s ) and i s h e a v i e r t h a n a i r .

*"Boron T r i f l u o r i d e , " p . 33 f f . i n Matheson Gas Data Book, The Matheson Co., I n c . , East Rutherford, N . J . , 1961.

Boron t r i f l u o r i d e i s v e r y i r r i t a t i n g t o t h e r e s p i r a t o r y

Toxicity. tract.

Exposure of t h e s k i n or eyes or t h e b r e a t h i n g of boron t r i -

f l u o r i d e should be avoided.

Although t h e r e l a t i v e t o x i c i t y of t h e gas

t o humans has n o t been e s t a b l i s h e d , no medical evidence of chronic eff e c t s has been found among workmen who have f r e q u e n t l y been exposed t o

small amounts f o r p e r i o d s up t o seven y e a r s .

A t high concentrations

boron t r i f l u o r i d e will cause burns on t h e s k i n similar t o , b u t n o t as p e n e t r a t i n g as, hydrogen f l u o r i d e . F i r s t - a i d suggestions.

t r i a l Hygiene Department.

Observe procedures s p e c i f i e d by t h e IndusIf o f f i c i a l procedures are n o t a v a i l a b l e ,

treat i r r i t a t i o n or burns of t h e eyes or s k i n w i t h copious amounts of water and o b t a i n s e r v i c e s of a p h y s i c i a n or t r a i n e d c l i n i c i a n as soon

as p o s s i b l e .

The t r e a t m e n t of BFa burns i s normally t h e same as t h a t

used f o r anhydrous hydrogen f l u o r i d e b u r n s . P r e c a u t i o n s i n h a n d l i n g and s t o r a g e .

The f o l l o w i n g r u l e s should be

followed i n t h e handling and s t o r a g e of boron t r i f l u o r i d e . 1. Cylinders should be s t o r e d i n a dry, c o o l , w e l l - v e n t i l a t e d area.

Cylinders may be s t o r e d i n t h e open, b u t i n such c a s e s should be prot e c t e d a g a i n s t extreme weather and from t h e dampness of t h e ground t o prevent r u s t i n g . 2.

Since Ssoron t r i f l u o r i d e i s r e a c t i v e w i t h water, a l c o h o l , e t h e r ,

and o t h e r compounds, i a t r o d u c t i o n of t h e gas below t h e s u r f a c e of a l i q u i d may c r e a t e a hazard owing t o t h e p o s s i b i l i t y of suckback i n t o t h e cylinder.

This should be guarded a g a i n s t by t h e use of t r a p s or check

valves.

Equipment exposed t o boron t r i f l u o r i d e should not b e used w i t h

o t h e r g a s e s , p a r t i c u l a r l y oxygen, s i n c e t h e gas may have o i l kapors t h a t

w i l l c o a t out on equipment and may cause f i r e s when combined with oxygen under p r e s s u r e .

Leak d e t e c t i o n .

Small l e a k s may be d e t e c t e d v i s u a l l y by checking

f o r an accumulation of f l u i d (product of r e a c t i o n between BF, and atmos p h e r i c m o i s t u r e ) or w i t h t h e a i d of an aqueous ammonia squeeze b o t t l e ( f o r m a t i o n of w h i t e fumes).

If t h e l e a k i s l a r g e enough, r e a c t i o n w i t h

atmospheric moisture will produce v i s i b l e "smoke. I t

117 W

Materials of c o n s t r u c t i o n .

Dry boron t r i f l u o r i d e does not r e a c t

w i t h t h e common metals of c o n s t r u c t i o n , b u t i f moisture i s p r e s e n t , t h e h y d r a t e a c i d s i d e n t i f i e d above can corrode a l l common metals r a p i d l y . I n consequence, l i n e s and p r e s s u r e reducing v a l v e s i n boron t r i f l u o r i d e s e r v i c e must b e w e l l p r o t e c t e d from moist a i r .

Cast i r o n must not be

used because a c t i v e f l u o r i d e a t t a c k s it s t r u c t u r e .

If s t e e l p i p i n g i s

used f o r boron t r i f l u o r i d e , forged s t e e l f i t t i n g s must be used w i t h it i n s t e a d of c a s t i r o n f i t t i n g s .

Materials recommended f o r t h e handling

of d r y boron t r i f l u o r i d e are s t e e l t u b i n g o r p i p e , s t a i n l e s s s t e e l , copper, n i c k e l , Monel, brass, and aluminum, and t h e more noble metals. These metals w i l l s t a n d up adequately t o a t l e a s t 200째C. i s a l s o suitable up t o about 200째C a t low p r e s s u r e s .

Pyrex g l a s s

For moist g a s :

copper, Saran t u b i n g , h a r d rubber, p a r a f f i n w a x , and Pyrex g l a s s show f a i r r e s i s t a n c e ; p l a s t i c materials, such as Teflon, Epons, polyethylene,

and pure p o l y v i n y l c h l o r i d e are n o t a t t a c k e d a t 80"c; rubber t u b i n g , phenolic r e s i n s , nylon, c e l l u l o s e , and commercial p o l y v i n y l c h l o r i d e are readily attacked. Chemical p r o p e r t i e s .

( a ) With elements:

A l k a l i and a l k a l i n e - e a r t h

metals reduce boron t r i f l u o r i d e t o elemental boron and t h e metal f l u o r i d e . Gaseous o r l i q u i d boron t r i f l u o r i d e does not r e a c t w i t h mercury or chromium, even a t h i g h p r e s s u r e s f o r long p e r i o d s .

Red-hot i r o n i s n o t

a t t a c k e d by boron t r i f l u o r i d e . ( b ) With oxides:

When boron t r i f l u o r i d e i s allowed t o r e a c t w i t h

s l a k e d l i m e , calcium b o r a t e and f l u o r o b o r a t e are formed w i t h e v o l u t i o n of h e a t .

With anhydrous calcium oxide o r magnesium oxide, t h e metal

f l u o r i d e and t h e v o l a t i l e boron o x y f l u o r i d e are formed. ( c ) With h a l i d e s :

BCl,

and BF,

do n o t r e a c t when h e a t e d t o 500째C.

Aluminum c h l o r i d e or aluminum bromide r e a c t w i t h boron t r i f l u o r i d e when g e n t l y h e a t e d t o g i v e t h e corresponding boron h a l i d e and aluminum f l u o ride.

Boron t r i f l u o r i d e forms no c o o r d i n a t i o n compounds when passed a t

1 a t m over t h e s o l i d c h l o r i d e s of copper, s i l v e r , or potassium a t t e m p e r a t u r e s from -75 t o 530째C.

(d) A s a c a t a l y s t :

Boron t r i f l u o r i d e a c t s as an a c i d c a t a l y s t .

c a t a l y z e s numerous t y p e s of r e a c t i o n s , namely, e s t e r i f i c a t i o n , n i t r a t i o n s , oxidations, reductions, halogenations, e t c .

A.5

Inconel and Hastelloy N Nominal composition ( w t %)

Inconel Hastelloy N

A.6

Fe -

0.04 0.06

0.35

0.20

0.50

Helium and Argon

Molecular weight Specific volume, f t 3/1bm 1

Specific heat, Btu l b - I mole-

Thermal conductivity, Btu hr1

Viscosity, l b m ft- sec

-1

("~)-l

ft-' ( O F ) -

, 32"F, 1 atm

Helium

Argon

5 .oo

0.0094

0.082 5

1.25 x io-

1.43 x io-

ORNL-DWG 67-9 4 2 3 A R

LIQUIDUS

800

-Yaz W

LIQUID-

700

600 (L

500

-c

400 t384"C 300

I--

200 NaF

---

NOF

+ NOBF,

I .

40 NaBF,

Fig. A . l .

--__

NaF + NaBF4 (HIGH-TEMPERATURE FORM)_-

243째C

+ LIQUID

- +

60 (mole

& _ -

NaBF4

Phase diagram for the system NaF-NaBF4.

120

ORNL-DWG

. - +

-+ -3

c-y

1 - i

c,c--_ 8CO

F i g . A.2.

9CC

7 2 - 2096

7+- t---+-----i I I

l3CC 1lOC 1200 TEMPERATURE ( O F )

1300

1400

BF3 p a r t i a l p r e s s u r e vs t e m p e r a t u r e f o r NaF-NaBF4 m i x t u r e s .

121 Appendix B REFEREINCE DRAWINGS"

ORNL Dwg. No.

Title

D-48942 D- 48944

Flow Diagram for Fluoroborate C i r c u l a t i o n Test

D-2-02-054-9779 D-2-02-054-9780 D-2-02-054-9783 D-2-02-054-9784 D-2-02-054-9785 D-KH-Z-41778

Flow Diagram Be Molten S a l t PKP-1 Pump T e s t Loop

Elementary E l e c t r i c Schematic for Fluorokorate C i r c u l a t i o n Test

A l a r m Schematic

E l e c t r i c Heater Layout Thermocouple Layout

Gas Control Cabinet Capillary Restrictor

Q-1512A-lRD

Thermal Conductivity C e l l Power Supply

s~-m-11-20-68 B-2-02-054-1926 B-2-02-054-1927 D-2-02-054-7440

R e s i s t a n c e Type Level I n d i c a t o r

*Partial l i s t i n g .

F l u i d Line for Freeze Valve A i r Tube for Freeze Valve Sample Device

122 Appendix C

MATERIAL SPECIFICATIONS NaBF, -

C.l

The sodium f l u o r o b o r a t e used i n t h e PKP f l u o r o b o r a t e c i r c u l a t i o n

t e s t w a s r e c e i v e d under Order No. 33~-63903, A p r i l 10, 1967, from t h e Harshaw Chemical Company.

The vendor g i v e s (memo of 5-12-67) t h e chemi-

c a l a n a l y s i s as follows ( w t %) :

NaBF,

C.2

99.08

0.01

0.023

0.025

0.004

Water i n s o l u b l e

0.01

Hi30

<O .01

0.01

NaF -

The sodium f l u o r i d e used w a s cp grade o b t a i n e d from Laboratory Stores.

(2.3 BF3 The BF3 w a s purchased from J. T. Baker Chemical Company under Order

No. 79s-1266, August 28, 1967.

Our s p e c i f i c a t i o n w a s as f o l l o w s :

EF3 minimum, 99.7$ v/v Maximum impurities,

â&#x20AC;&#x2122;$ v/v

A i r o r noncondensables

0.65

SOa

0.001

so3

0.001

SiF4

0.02

W e d i d not analyze f o r i m p u r i t i e s a t ORNL.

We d i d , however, make

a t e s t a t t h e f a c i l i t y i n an attempt t o determine i f t h e r e w a s any water or hydroxyl compounds i n t h e BF,.

The t e s t c o n s i s t e d i n p a s s i n g

several l i t e r s of t h e BF3 through a d r y - i c e t r a p and t h e n a n a l y z i n g t h e t r a p c o n t e n t s u s i n g t h e K a r l F i s c h e r method. found

No evidence of water w a s

Appendix D

DERIVATION OF EQUATION FOR CALCULATION OF BF3 PARTIAL PRESSURE

From R e f . 6:

€$

where f = mole f r a c t i o n NaBF,, p a r t i a l p r e s s u r e of BF,.

= e q u i l i b r i u m q u o t i e n t , and Pb =

Rearranging:

Also, from R e f . 5, Q v a r i e s with temperature: P

Q = exp(C P

B . - F)

Then b' For a

f B (m) [ex??(c - F)]

92-8mix:

and

11.5 jexp(C

i)]

also

In Pb From R e f .

2.442 + C - T

5: 10g(Pb, mm Hg) =

9.024- T5920 "K '

but

In P

2.303 l o g

pb =

= 20.782 - + .24 540 20.782 - 13~633 T OK T R

;

Then ln(Pb, p s i ) =

16.837 - 24 540

Comparing Eqs. ( 7 ) and (11):

2.442 + C S u b s t i t u t i n g i n Eq.

(4):

16.837 and C

14.395; B

24,540

Appendix E

FREEZE-THAW STRESS TEST A s t h e s a l t temperature i s b e i n g i n c r e a s e d , t h e r e i s an a b r u p t s o l i d -

state expansion ( d e n s i t y d e c r e a s e ) of about 15% when t h e temperature reaches

469째F.

This phenomenon i n t r o d u c e s t h e t h r e a t of damaging s t r e s s e s

i n s a l t - f i l l e d components i f t h e s a l t i s cooled below t h e t r a n s i t i o n t e m p e r a t u r e and t h e n r e h e a t e d . A bench t e s t w a s run t o s t u d y t h e e f f e c t of v a r i a t i o n s i n h e a t i n g technique.

A 2 - i n . - I D by 1 8 - i n . - l o n g Pyrex g l a s s t u b e w a s f i l l e d w i t h

t h e f l u o r o b o r a t e e u t e c t i c mixture t o a depth of about 8 i n . f u r n i s h e d by a Calrod h e l i x whose i n s i d e diameter w a s about

Heat w a s

1/4 i n .

l a r g e r t h a n t h e o u t s i d e diameter of t h e g l a s s t u b e , s o t h a t h e a t t r a n s mission w a s l a r g e l y by r a d i a t i o n . t h e assembly.

An aluminum f o i l r e f l e c t o r surrounded

Thermocouples were used t o i n d i c a t e t h e s u r f a c e temperature

of t h e h e a t e r and t h e s a l t temperature on t h e t u b e c e n t e r l i n e about 2 i n . from t h e bottom.

The t e s t assembly w a s t h e n o p e r a t e d through t h r e e t h e r -

m a l c y c l e s d u r i n g which t h e s a l t w a s melted and t h e n r e f r o z e n .

In a l l

t h r e e heatups, t h e h e a t e r temperature (Th i n F i g . E.l) w a s c o n t r o l l e d a t from

75 t o 300째F above t h e s a l t m e l t i n g temperature, and i n a l l t h r e e

c a s e s t h e m e l t i n g w a s accomplished without d i f f i c u l t y .

Then a f o u r t h

heatup w a s made wherein t h e h e a t e r temperature w a s c o n t r o l l e d below t h e m e l t i n g p o i n t of t h e s a l t . r e g i s t e r e d about

455 OF,

I n t h i s case, when t h e s a l t temperature Ts

t h e Pyrex t u b e suddenly s h a t t e r e d .

The conclusion i s t h a t t h e poor thermal c o n d u c t i v i t y of t h e f r o z e n

s a l t causes a s t e e p temperature g r a d i e n t , and, where t h e h e a t e r temperature i s above t h e m e l t i n g p o i n t , a f i l m of l i q u i d s a l t forms a t t h e salt c o n t a i n e r i n t e r f a c e b e f o r e t h e b u l k s a l t temperature reaches t h e s o l i d phase t r a n s i t i o n p o i n t .

The l i q u i d f i l m s e r v e s t o provide a n expansion

space t o p r o t e c t t h e c o n t a i n e r d u r i n g t h e phase t r a n s i t i o n of t h e b u l k

salt.

The results of t h i s t e s t suggest t h a t , whenever t h e s a l t tempera-

ture i s r a i s e d through t h e s o l i d phase t r a n s i t i o n p o i n t , mechanical

stresses can b e minimized by proper c o n t r o l of h e a t e r t e m p e r a t u r e . w i l l be n e c e s s a r y t o c o n s i d e r o t h e r f a c t o r s , however, such as system

126 geometry and t h e p r o b a b i l i t y and p o s s i b l e e f f e c t s of s h i f t i n g and packing of s a l t c r y s t a l s , b e f o r e one can p r o p e r l y assess t h e s o l i d phase t r a n s i t i o n problem.

ORNL- DWG 72-2097

2000 -

I -

+SALT ,500 --e- hEATER

TEMPERATURE, Th

2 i n DIAM PYREX GLASS TUBE

(z W

HEATER COIL (z

R w b-

1500

TEST APPARATUS

MELT CYCLE NO 2

Fig. E.l.

2 TIME I h r l

Data from fiuoroborate freeze-thaw s t r e s s t e s t .

ORNL-TM-3344

-wf

Internal Distribution

1. R. F. Apple 2. S . E . B e a l l M. E. E. R. S E. W. 10-13. J. 14. F. 15 * J. 16. A. 17. R . 18. W. 19-23. A. 24. R . 25. P. 26. R . 27* H . 28. W. 29. W. 30. P. 31.. J. 32 A. 33 J. 34. M. 35 * R . 36 * R.

Bender S. B e t t i s G . Bohlmann B. Briggs Cantor L. Compere B. C o t t r e l l L. Crowley L. C u l l e r R . Engel P. Fraas B. G a l l a h e r R. G r i m e s G. Grindell H . Guymon N. Haubenreich E. H e l m s W. Hoffman R. Huntley H . Jordan R. Kasten W. Koger I . Krakoviak W. Krewson I. Lundin N. Lyon E . MacPherson H . E . McCoy 37. H. C. McCurdy 38

3. 4. 5. 6. 7. 8. 9.

39. L. E. McNeese 40. J. R . McWherter 41. H . J. Metz 42. A. S . Meyer 43. A. J. Miller 44. R . L. Moore 45. A. M . Perry 46. R . C . Robertson 47. M. W. Rosenthal 48. H. C . Savage 49-52. Dunlap S c o t t 53- J. H . S h a f f e r 54. M. R . Sheldon 55. M. J. Skinner 56-58. A. N . Smith 59. I . Spiewak 60. R . D. S t u l t i n g 61. D . A. Sundberg 62. E. H . Taylor 63. R . E. Thoma 64. D. B. Trauger 65. A. M. Weinberg 66. G. D . Whitman 67. L . V . Wilson 68. Gale Young 69. H . C . Young 70-71. C e n t r a l Research

Library

Y-12 Document Reference S e c t i o n Laboratory Records Department Laboratory Records Department (RC)

External Distribution

78. A. 79-80. C . 81. 82. 83-84. 85.

A g o s t i n e l l i , Worthington Corporation, H a r r i s o n , N . J . 07029 E. Anthony, Electro-Mechanical D i v i s i o n , Westinghouse E l e c t r i c Corporation, Box 217, Cheswick, Pa. 15024 F. F. Antunes, Ingersoll-Rand Company, Cameron Engineering D i v i s i o n , P h i l l i p s b u r g , N . J . 08865 R . G. B a r r e t t , F o s t e r Wheeler, L i v i n g s t o n , N . J . 07039 R. N. Bowman, Pump D i v i s i o n , Bingham-Willamette Company, 2800 N.W. Front Avenue, P o r t l a n d , Ore. 97210 A. H . Church, Mechanical Engineering Department, New York U n i v e r s l t y , Bronx, N.Y. 10400

86-87. 88. 89. 90.

91. 92.

93. 94.

95 * 96. 97 * 98. 99. 100. 101. 102. 103. 104-105.

106.

107. 108. 109. 110.

111. 112.

113. 114. 115-132. 133- 134. 135-137 138-139.

Gary Clasby, Byron Jackson Pumps, I n c . , P.O. Box 2017, Terminal Annex, Los Angeles, Calif. 90054 D . F. Cope, RET, SSR, AEC, ORNL V . R. Degner, Rocketdyne Division, North American Aviation, Canoga Park, C a l i f . 91303 A. R. DeGrazia, RDT, USAEC, Washington, D . C . 20545 D. E l i a s , RDT, USAEC, Washington, D . C . 20545 J. R . Fox, USAEC, Washington, D . C . 20000 A. Giambusso, USAEC, Washington, D . C . 20000 F. C . Gilman, Fump and Heat T r a n s f e r D i v i s i o n , Worthington Corporation, Harrison, N . J . 07029 R . Gordon, Aerojet-General, Azusa, C a l i f . 91702 C . W. Grennan, Colt I n d u s t r i e s , Chandler Evans Control Systems Division, West H a r t f o r d , Conn. 06100 Norton Haberman, USAEC, Washington, D . C . 20000 F. G. H a m m i t t , The U n i v e r s i t y of Michigan, Ann Arbor, Mich. 48103 M. J. Hartmann, NASA-Lewis Research Center, Cleveland, Ohio 44100 C . H . Hauser, ITMA-Lewis Research Center, Cleveland, Ohio 44100 J. W. H o l l , Pennsylvania S t a t e U n i v e r s i t y , G a r f i e l d Thomas Water Tunnel, Ordnance Research Laboratory, U n i v e r s i t y Park, Pa. 16802 Kermit Laughon, USAEC, OSR, ORNL Liquid Metal Engineering Center, c / o Atomics I n t e r n a t i o n a l , P.O. Box 309, Canoga Park, C a l i f . 91303 ( A t t e n t i o n : R. W . Dickinson) T. W. McIntosh, USAEC, Washington, D . C . 20000 D. C . Reemsnyder, NASA-Lewis Research Center, Cleveland, Ohio 44100 M. A. Rosen, DRDT, USAEC, Washington, D . C . 20000 R e s e a r c h and T e c h n i c a l Support D i v i s i o n , O R 0 M. Shaw, USAEC, Washington, D.C. 20000 W. L . Smalley, USAEC, Oak Ridge Operations W . A. Spraker, Engineering Research D i v i s i o n , S c o t t Paper Company, P h i l a d e l p h i a , Pa. 19100 H . A. S t a h l , Cameron Division, Ingersoll-Rand Company, P h i l l i p s b u r g , N.J. 08865 B. S t e r n l i c h t , Mechanical Technology, I n c . , Latham, N . Y . 12100 G . M. Wood, ?ratt and Whitney A i r c r a f t Corporation, E a s t H a r t f o r d , Conn. 06100 Manager, T e c h n i c a l I n f o r m a t i o n C e n t e r , AEC Technical Information Center (AEC) D i r e c t o r of D i v i s i o n of Reactor Licensing, Washington, D . C . 20545 D i r e c t o r of D i v i s i o n of Reactor Standards, Washington, D . C . 20545