- 62
-
In t h e s a l t r e g i o n of Area C, a few small in-tergranii1.a~c r a c k s
were found on t h e i n t e r i o r of t h e v e s s e l wall.
A typical. crack i s shown i.n
t h e unetched condi.tion i n F i g . 26 a n d i n t h e e t c h e d c o n d i t i o n i.n Fig, 22.
Very pronounced darkening of t h e g r a i n boundaries t o approxi-mately t h e same depth as the crack was evi.dent a f t e r e-tching.
Cross s e c t i o n s from t h e f l . u o r i n a t o r s h e l l longitudi.na1 weld a r e
shown i.n Fig. 27 (Samples B-8T and A-3b) which d e p i c t s s e c t i o n s i.n t h e vapor
and sal..t phases, r e s p e c t i v e l y .
The weld. j o i n t from t h e s a l t regi.on shows
This confirrns t h e
what, appears t o be a n i n c r e a s e d a t t a c k a t tile weld r o o t .
v i s u a l examinations of t h e Mark 11 f l u o r i n . a t o r .
Examination of t h e weld from
t h e s a l t s e c t i o n a t bigk inagnif i c a t i o n r e v e a l e d pronounced grai.n-boundary
darkening a f t e r e t c h i n g t o a maximum depth o f 10 mils,
Similar, deeper g r a i n -
boundary darkening occurred rin t h e base metal a d j a c e n t t o the weld metal, extending t o a maximum depth of 33 m i l s .
The e x ' i e r i ~ o rof t h e vessel d i s p l a y e d a c o r r o s i v e a t t a c k which
appeared t o be i n t e r g r a n u l a r i n nat71re.
P e n e t r a t i.on v s r i e d Prom
1-6
mils, t h e
maximum o c c u r r i n g a t o r below Lhe v a p o r - s a l t i n t e r f a c e (Fig.. 28, Samp1.e A-3b). However, t h e r e w a s one e x c e p t i o n t o t11ri.s pa+,tern.
A grain-boundary peaetrat,ion
of approx 1 2 m i l s i.n depth was found on -the e x t e r i o r s u r f a c e o p p o s i t e tile
p i t t e d r e g i o n i n t h e vapor n e a r Area C.
5.
Summary o f Corrosive Attack ____ Table I X summarizes t h e corrosion l o s s e s of al..l. t y p e s found i n
the t h r e e major r e g i o n s of t h e Mark I1 VPP
L nickel fluorinator.
?'he ma-ximum
a t t a c k w a n cal-culated t o be 60 mils/month based on exposure -Lo molten s a l t s durring t h e VPP "E" r u n s
(1.-6) and "L" mils (1-9)
o r 1.1 rnils/hr based on
f l u o r i n e sparge time d u r i n g f l u o r i n a t i o n of molten s a l t s
e
The maximum a t t a c k
occiirred in t h e s a l t region.
Y.
Discussion o f R e s u l t s The Mark I1 VPP L n j c k e l f l u o r i n a t o r d i s p l a y e d a rnaximurn c o r r o s i o n
a t t a c k d u r i n g t h e d e s c r i b e d VPF runs o f 1.1 mils/hr, based on F sparge time 2 during flixorinaiion, o r 60 mils/month, based on molten- s a l t r e s i d e n c e tiiiie