Development of advanced PRA model for Shimane Unit 2 internal event at-power

Abstract

An importance for risk management has come to be re-recognized in Japan after the accident of the Fukushima Daiichi nuclear power plants. A Probabilistic Risk Assessment (PRA) fulfills a significantly important role in the framework of the risk management. Technical adequacy of PRA model and high quality of data are required in order to utilize PRA for such risk-informed activities. Therefore, Japanese utilities launched the project for enhancing the quality of PRA models and are upgrading PRA models to comply with international standards. Chugoku Electric Power Company (Chugoku) is also upgrading the internal events at power PRA model including both the level 1 and level 2 (except the source term analysis) and enhancing PRA quality in order to utilize risk insight for improving nuclear safety. The aim of the PRA upgrade is to reflect international state-of-the-practice approaches and to meet ASME/ANS PRA standard (ASME/ANS 2013) requirements (Capability Category II). Our PRA upgrading process is divided into 3 phases: “Phase I”, “Phase II” and “As-is”. This paper reports the detail of PRA upgrade implemented in Phase I and Phase II such as initiating event refinement, accident sequence re-evaluation, detailed fault tree (FT) analyses, modeling severe accident measures and updating human reliability analysis (HRA).

Keywords

• probabilistic risk assessment (pra)
• risk informed decision making (ridm)
• fault tree (ft) analysis
• human reliability analysis (hra)
• core damage frequency (cdf)
• containment failure frequency (cff)