Development of Source Term Evaluation Method Applicable to Dynamic PRA

Abstract

　The objective of this study is to develop a source term evaluation method applicable to a dynamic probabilistic risk assessment (PRA) for a level 2 PRA. The dynamic PRA for a level 2 PRA needs a method that can calculate the behaviors of fission products (FPs) in nuclear power plants (NPPs) during a severe accident (SA) appropriately with much a smaller calculation load than that of existing SA analysis methods. In this study, a new method called the source term phenomenological relationship diagram (PRD) is developed by applying the PRD method. The source term PRD consists of the major phenomena related to FP behaviors and their quantification processes. The trial evaluation of the method is conducted for a long-term station blackout scenario. The FP behaviors evaluated using the source term PRD are consistent with those obtained by the conventional SA analysis with a much smaller computational load than that of the conventional SA analysis methods. These facts verify that the source term PRD is applicable to a level 2 dynamic PRA. In the future, the analysis of the source term PRD coupled with thermal hydraulic analysis will be conducted for the establishment of the level 2 dynamic PRA.