37
steam t o d r i v e t h e t u r b o g e n e r a t o r s .
Thus two c o o l a n t s could be employed,
n e i t h e r of which meet a1.L t h e c o o l a n t c r i t e r i a .
Dual c o o l a n t configura-
t i o n s which appear t o be t h e most a t t r a c t i v e w i l l be d i s c u s s e d i n d e t a i l i n S e c t i o n 7.
The purpose of t h i s s u b s e c t i o n i s t o i d e n t i f y t h e f l u i d s
t h a t are a c c e p t a b l e i n secondary and t e r t i a r y loops.
4.2.1
-
Secondary c o o l a n t s
O f a l l t h e f l u i d s r e j e c t e d i n t h i s s e c t i o n , o n l y molten LiF-BeF2
m i x t u r e s are c l e a r l y a c c e p t a b l e secondary c o o l a n t s .
The c r i t e r i a f o r r e -
j e c t i n g a l l t h e o t h e r s a:; s i n g l e secondary c o o l a n t s a l s o apply f o r r e j e c t i n g them as secondary c o o l a n t s i n d u a l c o o l a n t c o n f i g u r a t i o n s .
They
e i t h e r would pose s a f e t y problems i f l e a k s o c c u r r e d i n t h e primary h e a t exchangers o r e l s e t h e y are t o o c o r r o s i v e toward s t r u c t u r a l a l l o y s .
4.2.2
T e r t i a r y (steam-raising) coolants
I t was assumed t h a t t h e prime purpose o f an a d d i t i o n a l c o o l a n t loop i s t o p r o v i d e t h e means for s e q u e s t e r i n g t r i t i u m .
Hence, any f l u i d t h a t
cannot do t h i s a t r e a s o n a b l e c o s t while m a i n t a i n i n g a t o l e r a b l e r a t e o f c o r r o s i o n was n o t considered a c c e p t a b l e .
N i t r a t e s and n i t r i t e s decompose
a t t o o low a temperature t o w a r r a n t s e r i o u s c o n s i d e r a t i o n .
Heavy metals
as w e l l as t h e s a l t s w i t h r e d u c i b l e i o n s mentioned i n S e c t i o n 4.1.2 e l i m i n a t e d from f u r t h e r c o n s i d e r a t i o n on t h e same b a s i s ( c o r r o s i v i t y which t h e y were d i s c o u n t e d as secondary c o o l a n t s .
are by
Sodium i s n o t l i k e l y
t o s e q u e s t e r enough of t h e t r i t i u m t o be an a c c e p t a b l e t e r t i a r y c o o l a n t . Helium or t h e t e r n a r y e u t e c t i c (Na, L i , K12C03 are t h e two most a t t r a c t i v e t e r t i a r y coolants i d e n t i f i e d i n t h i s study. The use of n i t r a t e - n i t r i t e mixtures as a s t e a m - r a i s i n g c o o l a n t has