300 Study on the PSA Model Considering the Symmetrization of Operational Train Patterns and Loops Affected by Initiating Events (PSAM-0119)

We developed the upgraded PSA models considering the symmetrization of operational train patterns and loops affected by initiating events. There was not difference in the evaluation results of CDFs between one of the upgraded models and one of the conventional models. It means that the assumptions of fixed operational trains and fixed loops affected by initiating events are valid. But in the view of risk importance evaluation, the risk importances of similar rotational components in the same system are different in the conventional model. However, they are almost equal in the upgraded model. This upgraded model can supply a more accurate risk importance index for risk-informed activities, such as RI-IST.

This upgraded model describes appropriate component's state according to average plant states, and so can be effectively used as a base line model for the living mode evaluation, such as OLM.