Analysis of long-term DHR System Performance for a LMR

Conclusions: • The demonstration of the «Non credibility» of the situation related to the long - term loss of DHR function is organized through: – Probabilistic assessment approach; – Demonstration of negligible risk; – Probabilistic goals. • Results show the inadequacy of design measures to meet the safety requirement of 10-7/reactor year: – System redundancies and configuration. • Results subject to the assumptions taken in the analysis: – Lack of statistically reliable data for LMRs; – Level of definition of the systems, which are not yet established; – Conservative value of the frequency of the initiator, corresponding to the normal shutdown. • Results show the relevance of CCFs; • Other provisions that could justify the "practical elimination": – Diversification of components to cope with CCFs; – DHR function through vault cooling