- 117 The off-gas system, because of the high a c t i v i t y , would have t o be maintained remotely. Because of the p o s s i b i l i t y of f i s s i o n product gases leaking i n t o the system i n the reference design, t h e equipment f o r the helium preheating and cooling systems, e.g. blowers, e l e c t r i c heaters, and cooler would be located i n a limited access area of the p l a n t and sealed i n individual containment vessels. Maintenance on t h i s system's components would be by d i r e c t contact means when the system i s not i n operation, I f t h e components become too radioactive and cannot be deontaminated, they w i l l be destroyed by remote means and replaced.
The fan d r i v e motor f o r the c e l l v e n t i l a t i n g system which would be mounted above t h e plug, would be maintained d i r e c t l y . Work on t h e air fan and cooling c o i l s would be done i n t h e hot shop a f t e r t h e u n i t is removed from the c e l l . The air v e n t i l a t i o n system f o r t h e hot areas of t h e plant would have t o be located i n a c e l l with means f o r decontamination of remote maintenance of t h e fans, motors, and f i l t e r s . I n the reference design, t h i s system i s outside the shielded p a r t o f t h e plant.
The instrumentation and the methods of maintenance have not been studied i n d e t a i l . Some work has been done on a l e a k detection system f o r the primary system. T h i s detection system i s very important s i n c e all components and piping are enclosed by an outer sealed container. The detection system must serve two functions; show t h a t a l e a k has occurred and give t h e location of the leak. A l l maintenance work i n t h e reactor, primary pump, and heat exchanger compartments below the main biological s h i e l d would be performed completely remotely. T h i s work would include replacing the heat exchanger s h e l l s , pump casings, primary piping, dump tanks and t h e i r piping, and all instrumentation not accessible from t h e access canyon. The maintenance would be performed by mobile truck-mounted manipulators and t e l e v i s i o n viewing equipment. The mobile manipulat o r truck, its manipulators and t e l e v i s i o n equipment will be b a t t e r y powered and radio controlled.
Two remote control trucks are under t e s t t o demonstrate the f e a s i b i l i t y of t h i s concept of maintenance. The basic maintenance concept, using mobile trucks, w i l l require extensive t e s t i n g . I n summary, the major probbems of maintenance have been recognized and engineering work i s underway t o solve them.