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Figure 13 shows t h e r e s u l t s of a d i g i t a l calculation of the t r a n s i e n t s produced by the rod withdrawal with f u e l C i n the reactor. The power a t k = 1 w a s 2 mw, the minimum attainable with only t h e inherent CY-n neutron source present. If nothing were done t o stop t h e rods, it i s c l e a r t h a t intolerable temperatures would be reached. A rod scram a t 15 Mw can l i m i t the temperature excursion t o a tolerable value, even i f it i s assumed t h a t one of t h e three clutches f a i l s t o disengage. The e f f e c t of dropping two control rods, while the t h i r d continues t o withdraw, i s shown i n Fig. 14. The actual response time of a prototype cont r o l rod w a s much shorter than that assumed f o r t h i s analysis. The f i l l i n g accident represents a special case because the amount of r e a c t i v i t y available i s not limited t o t h a t associated with a normal f u e l loading. Prior t o f i l l i n g t h e reactor, the control rods w i l l be withdrawn so t h a t the core i s j u s t s l i g h t l y s u b c r i t i c a l when completely full. T h i s provides a capability f o r rapid i n s e r t i o n of negative react i v i t y i n the event of a power excursion during f i l l i n g . However, the r e a c t i v i t y t h a t could be added i n t h e postulated accident i s greater

UNCLASSIFIED ORNL-DWG 64-8477A

a W 3

5

a a H W c W

a

W

xB " 0

! *

2

4

6

8 40 TIME (sed

12

44

46

Fig. 13. Power and Temperature Transients Produced by Uncontrolled Rod Withdrawal, Fuel C.

ORNL-3708  

http://www.energyfromthorium.com/pdf/ORNL-3708.pdf

ORNL-3708  

http://www.energyfromthorium.com/pdf/ORNL-3708.pdf

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