is formed i n d i r e c t l y by decay o f 6.7-hrstream s t r i p p i n g of
13%,
and t h e u s e of r a p i d s i d e -
by t h e r e a c t i o n
was c o n s i d e r e d a remote p o s s i b i l i t y f o r t h e TvISBR.~ Such s t r i p p i n g seems a m o s t u n l i k e l y need f o r t h e DMSR; i f i t were n e c e s s a r y , i t would p r e c l u d e o p e r a t i o n a t h i g h UF?/UFL,r a t i o s . The rare e a r t h s and o t h e r s t a b l e s o l u b l e f l u o r i d e s (e.g.,
Zr, C e ,
S r , C s , P, B a , and Rb) are a l l e x p e c t e d t o b e found p r i n c i p a l l y i n t h e f u c l salt:k and can b e removed by t h e â‚Ź u e l p r o c e s s i n g o p e r a t i o n . t
?'lie
c h e m i c a l b e h a v i o r of t h e s e f i s s i o n p r o d u c t s i s f a i r l y w e l l u n d e r s t o o d a n d , 1 i i c c t h e noble-gas b e h a v i o r
o p e r a t i n g UMSRs
can be p r e d i c t e d c o n f i d e n t l y f o r
27
I h c c h e n i r a l b e h a v i o r of t h c s o - c a l l e d noble-metal
f i s s i o n products
(Nb, N o 9 Tc, liu, A g , Sb, and T e l l i s c o n s i d e r a b l y l e s s p r e d i c t a b L e
-
as
- and w a r r a n t s f u r t h e r s t u d y .
h a s been b o r n e o u t i n MSRE
According t u a v a i l a b l e thermodynamic d a t a , t h e y a r e e x p e c t e d t o a p p e a r i n a reduced form at L!FJ/UFL, r a t i o s g r e a t e r t h a n lo-'.
However, i n t h e
reduced and presuincxl m e t a l l i c s t a t e , t h e s e f i s s i o n p r o d u c t s can d i s p e r s e v i a many mechanisms. A n a l y s e s of MSRE sal t samples f o r f i v e n o b l e - m e t a l n u c l i d e s ("Ffo, I O
106
qRu
Ru, and
129-137
Te) showed t h a t t h e f u e l sa16 c o n t a i n e d up t o
a P e w t e n s o f p e r c e n t of t h e nominal c a l c u l a t e d i n v e n t o r y .
A l l these
s p e c i e s have v o l a t i l e h i g h - v a l e n c e f l u o r i d e s t h a t c o u l d form under s u f f i c i e n t l y oxidizing conditions.
On t h e b a s i s of thermodynamic c o n s i d -
e r a t i o n s and a c o r r e l a t i o n of t h e i r b e h a v i o r with t h a t of l l l A g , f o r which no s t a b l e f l u o r i d e e x i s t s under f u e l - s a l t
c o n d i t i o n s , i t has been
t e n t a t i v e 1 y concluded t h a t t h e y a r e m e t a l l i c species t h a t o c c u r as f i n e l y d i v i d e d p a r t i c l e s suspended i n t h e salt
e
J-
Some of t h e s e have noble-gas p r e c u r s o r s ; a f r a c t i o n o f t h e s e w i l l e s c a p e from t h e f u e l and a p p e a r in t h e o f f - g a s system. I
S e e Chapter 6 .
r
And several o t h e r s p e c i e s of lower y i e l d .