38 f o r which we estimate'
the equilibrium quotient
The r e s u l t i s t h a t w i t h 100 ppm p r o t a c t i n i u m and 30 ppm o x i d e p r e s e n t , t h e U'+/W''+
r a t i o must b e k e p t above a b o u t
t i o n of Pap05 i s t o b e a v o i d e d . avoid i n p r a c t i c e .
i f inadvertent precipita-
Such o x i d i z i n g c o n d i t i o n s a r e e a s y t u
There i s a l s o a dependence on t h e C 3 * / U k +
t h e o x i d e c o n c e n t r a t i s n a t which PuOa p r e c i p i t a t i o n o c c u r s . even s t r o n g e r o x i d i z i n g c o n d i t i o n s (U 3 + / ~ 4 + <
r a t i o of However
~
are r e q u i r e d t o p r e -
c i p i t a t e Pu02 from f u e l f o r XSBKs o r DMSRs. T h e s o l u b i l i t y of t h e o x i d e s of neptunium, americium, o r curium has
n o t been examined.
Some a t t e n t i o n t o t h i s problem w i l l be r e q u i r e d , b u t
i t i s not o b v i o u s t h a t s u c h studies have a h i g h p r i o r i t y . Tt i s c l e a r t h a t t h e LIMSR f u e l m u s t be p r o t e c t e d f r o m o x i d e contami-
nation t o avoid inadvertent p r e c i p i t a t i o n .
Because of t h e l o w o x i d e
t o l e r a n c e , t h i s w i l l r e q u i r e some c a r e , b u t t h e s u c c e s s f u l o p e r a t i o n of t h e MSRE o v e r a 3-17ear p e r i o d l e n d s c o n f i d e n c e t h a t o x i d e c o n t a m i n a t i o n o f t h e f u e l s y s t e m can be k e p t t o a d e q u a t e l y Pow l e v e l s .
This confidence,
when added t o t h e p r o s p e c t t h a t t h e DMSR f u e l w i l l be r e p r o c e s s e d (and i t s o x i d e l e v e i r e d u c e d by f l u o r i n a t i o n of t h e uranium) on a c o n t i n u o u s
b a s i s , s u g g e s t s v e r y s t r o n g l y t h a t problems w i t h o x i d e c o n t a m i n a t i o n can be a v o i d e d . P h y s i c a l p r o p e r t i es. ThF4 (92-16-12
mole 7;)"
Most of the p h y s i c a l p r o p e r t i e s of LiF-ReFi-
a r e known w i t h r e a s o n a b l e a c c u r a c y , a l t h o u g h
s e v e r a l have been d e f i n e d by i n t e r p o l a t i o n from measurements on s l i g h t l y
d i f f e r e n t compositions. The l i q u i d u s t e m p e r a t u r e i s w e l l knswn, and d e n s i t y and v i s c o s i t y
a r e a c c u r a t e t o 23 and h10%, r e s p e c t i v e l y . been d e r i v e d from d r o p c a l o r i m e t r y ;
2,24
The h e a t c a p a c i t y h a s
on t h e b a s i s of t h i s d e t e r m i n a t i o n
and w i t h a s i m p l e model f o r p r e d i c t i n g h e a t c a p a c i t y of m o l t e n f l u o r i d e s , one c a n r e l i a b l y p r e d i c t t h e h e a t c a p a c i t y of t h e DNSR mixture.
v
Most p h y s i c a l p r o p e r t i e s w i l l be t r i v i a l l y a f f e c t e d by v a r i a t i o n s among t h e heavy-metal c u n c e n t r a t i o n s so l o n g as t h e heavy-metal c o n t e n t r e m a i n s a t 1 2 mole 2.