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bypassing t h e prototype stage and c o n s t r u c t i n g a l a r g e power r e a c t o r demonstration.
Such
a prototype program may a l s o be d e s i r a b l e f o r the SSCR, p a r t i c u l a r l y i f t h e prototype program i n v o l v e d t h e m o d i f i c a t i o n o f an e x i s t i n g PWR f o r s p e c t r a l - s h i f t c o n t r o l r a t h e r than the c o n s t r u c t i o n of a w h o l l y new p l a n t f o r t h i s purpose.
However, the estimates o f t h e
r e a c t o r R&D requirements given f o r the SSCR i n Table 5.1-2 are based on t h e assumption t h a t t h i s p r o t o t y p e stage i s bypassed.
This can be j u s t i f i e d on t h e basis t h a t the SSCR i s
r a t h e r unique among the various a l t e r n a t i v e s because o f i t s close r e l a t i o n s h i p t o present
PWR technology. I n p a r t i c u l a r , no r e a c t o r development would be r e q u i r e d and t h e r e a c t o r could be designed so t h a t the p l a n t would be operated i n e i t h e r t h e conventional poison c o n t r o l mode o r i n t h e s p e c t r a l - s h i f t c o n t r o l mode. As a r e s u l t , a g r e a t m a j o r i t y o f the c a p i t a l investment i n t h e p l a n t and the power output of the p l a n t i t s e l f i s n o t a t r i s k . Likewise, t h e p o t e n t i a l f o r serious l i c e n s i n g delays i s l a r g e l y mitigated, since the reac-
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t o r c o u l d i n i t i a l l y be operated as a poison-controlled PWR and e a s i l y reconfigured f o r the s p e c t r a l - s h i f t c o n t r o l once the l i c e n s i n g approvals were obtained. Consequently, t h e c a p i t a l a t r i s k i s l i m i t e d t o the a d d i t i o n a l expenditures r e q u i r e d t o r e a l i z e s p e c t r a l -
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s h i f t c o n t r o l , roughly $30 $60 m i l l i o n f o r component R&D, p l u s r e n t a l charges on the heavy water inventory. The a d d i t i o n a l expenditures f o r design and l i c e n s i n g , $20 $50
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m i l l i o n , would have a l s o been necessary f o r the prototype. The component R&D would c o n s i s t o f a thermal-hydraulic development task; valves and seal development; development o f design and t e s t i n g .
D20 upgrader technology; and r e f u e l i n g methods development,
The thermal-hydraulic t e s t s would be designed t o produce a departure
from nucleate b o i l i n g c o r r e l a t i o n f o r the SSCR moderator s i m i l a r t o t h a t which has been developed f o r t h e PWR l i g h t - w a t e r moderator.
The c o r r e l a t i o n s are expected t o be very
s i m i l a r , b u t t e s t s t o demonstrate t h i s assumption f o r t h e various mixtures o f heavy and l i g h t water w i l l be required. Valves and seal development w i l l be necessary i n order t o minimize leakage o f t h e heavy-water mixture; reduction o f coolant leakage i s important both from an economic standpoint (because o f t h e c o s t o f D20) and because of t h e p o t e n t i a l r a d i o l o g i c a l hazard from t r i t i u m which i s produced i n the coolant. Methods o f reducing coolant leakage from valves and seals have been e x t e n s i v e l y explored as p a r t o f t h e design e f f o r t on heavy-
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water r e a c t o r s and u t i l i z a t i o n o f heavy-water r e a c t o r experience i s assumed. The R&D program would address t h e a p p l i c a t i o n o f t h e technologies developed f o r the heavy-water r e a c t o r t o t h e l a r g e r s i z e components and higher pressures encountered i n t h e SSCR. The D20 upgrader employed i n t h e SSCR i s i d e n t i c a l i n concept t o t h e upgraders used on heavy-water r e a c t o r s and i n t h e l a s t stage ( f i n i s h i n g stage) o f D20 production f a c i l i t i e s . The s i z i n g o f various components i n the upgrader would, however, be somewhat d i f f e r e n t f o r
SSCR a p p l i c a t i o n because o f the range o f D20 concentration feeds ( r e s u l t i n g from t h e changing D20 concentration d u r i n g a r e a c t o r operating cycle), and because o f t h e l a r g e volume o f low D20 concentration coolant which must be upgraded toward the end o f each operating cycle.
The upgrader R&D program would consider t h e s i z i n g o f the upgrader,