COOLING SYSTEM FAILURES LEADING TO SEVERE ACCIDENTS IN WWER 440 REACTORS FOLLOWING SMALL BREAK LOCAs

摘要

COOLING SYSTEM FAILURES LEADING TO SEVERE ACCIDENTS IN WWER 440 REACTORS FOLLOWING SMALL BREAK LOCAs. In the paper, attention is devoted to failures of the high pressure injection system, which is the most important for prevention of severe core damage in the event of small break LOCAs in a WWER 440 reactor. Initiating small breaks in the primary system boundary with an equivalent diameter from 13 to 107 mm were analysed by means of the SLAP code. The aim was to evaluate time margins for the actions necessary to prevent substantial core uncovery and fuel melting as well as to verify the capability of the high pressure injection system. Results of the steady state and transient analysis are presented and discussed.