Reliability analysis of spray system of WWER-400 reactor unit (V230)

The spray system is used for pressure reduction and heat removal from the steam generator box and from the main circulation pump upon loss of steam-water mixture due to leaks. The system consists of three spray pumps, two heat exchangers, a boric acid tank, spray nozzles. The reliability analysis is explained using the system as an example. The Interim Reliability Evaluation Program technique is used. Failure trees are set up for the stand-by mode and for operation. With the given structure of the spray system the unavailability of the system upon call for action can be reduced by more frequent checks. It is expected that during reconstruction of V 230 reactor units the structure of the system will be changed by producing three independent channels. (M.D.). 2 figs., 3 tabs., 6 refs