Reliability enhancement of seismic risk assessment of NPP as risk management fundamentals, 1; Uncertainty analysis with the SECOM2 code

Muta, Hitoshi*; Muramatsu, Ken*; Furuya, Osamu*; Uchiyama, Tomoaki*; Nishida, Akemi  ; Takada, Tsuyoshi*  

Seismic PRA is an effective measure to consider the countermeasures and improvement plans to secure the further safety of nuclear power plants regarding to seismic risk for the earthquake exceeding the reference ground motion. However, the application of the seismic PRA has not been utilized sufficiently so far. One of the reasons is that there is not enough consensus among stakeholders regarding to the evaluation methods and consideration of uncertainty for decision-making. This study proposes the mathematic framework to treat the uncertainty properly related to the evaluation of Core Damage Frequency induced by earthquake, the method to evaluate the fragility utilizing expert knowledge, the probabilistic model to cope with the aleatory uncertainty as well as the development of analyzing code including these considerations for the improvement of the reliability of the method and enhancement of utilization of the products of Seismic PRA.