Indian Operating Experience in Level-1 PSA of VVER-1000 Type Reactors, (KKNPP-1&2)

The purpose of this paper is to provide a comprehensive summary of the experiences and results of Level-1 PSA in VVER-1000-type plants in Indian environmental conditions. This paper also gives insight into achieving the realistic results which have been used in risk-informed decision-making with high confidence. KKNPP-1&2 (Kudankulam Nuclear Power Plant) is a VVER-1000 type light water reactor which has been in operation since 2013 and has reasonable full-power reactor years of experience. The Indian operating experience has been captured in various stages of Level-1 PSA, like reliability parameter estimation, Initiating Event frequency estimation, modelling of Fault Trees etc., and in doing so, the first-ever Data Bank has been developed for Indian VVERs. These Data Bank will also act as baseline data for future Indian light water reactors. The system modelling has been done by considering realistic success criteria for safety systems. The internationally renowned software has been used for Fault Tree and Event Tree modelling. The CDF value achieved from the in-house study is in the order of 1E-07 per reactor per year, which compares favorably with the AERB and IAEA recommended values for full-scope PSA. This also provides sufficient margins for the contribution from Internal and External Hazards which is not considered in present study.