Simplified Level-1 Probabilistic Safety Assessment

Both deterministic and probabilistic approaches are important and useful for clarifying the safety characteristics of new reactors concepts. In this section, simplified level-1 PSA (probabilistic safety assessment) of the Super LWR is introduced. Information from preliminary PSA studies on the SCWR [21, 33] and PSA documents for US LWRs [34-37] and for Japanese LWRs [38-41] is mainly referred to in this section. 

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The possibility of repair during accident situation is yet to be included into Probabilistic Safety Assessment (PSA). A PSA method Includes Event tree (ET) to generate accident scenario and Fault Tree (FT) used to quantify the probability of failure of the Safety Barrier (SB). In literature, there are some examples in which FT analysis has been done for systems with repair components. A FT analysis of phased mission systems has been performed with repairable and non-repairable components (Vaurio 2001). The other FT models with repairable basic events have been proposed based on renewal intensity principle and inclusion-exclusion methods (Yuge et al. 2012 Yuge et al. 2013). However, ET analysis of Initiating Events (IE) with repairable SB has not been dealt before. Therefore this paper proposes a scheme of PSA level-1 for systems with repairable components using a simplified combination of Repairable Event Tree (RET) and Repairable Fault Tree (RFT). 

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