Development of risk monitoring tool for nuclear power plant applications using probabilistic risk assessment

Systematic and comprehensive Probabilistic Risk Assessment (PRA) uses to evaluate risks for the Nuclear Power Plant (NPP), and the risk information is also used to enhance the rationality and accountability of safety related activities, and to realize efficient management in NPPs. The regulatory and the industry are discussing the standard and guideline for the various types of PRA and management for the near-future actual usage. 'Risk Monitoring' is the essential item for the PRA usage and risk-informed activities, and we assume 'At-power risk monitoring in case of On-Line Maintenance' and 'Shutdown risk evaluation for every outage' are 2 key issues for 'Risk Monitoring'. Our company NEL has developed a risk monitoring tool called COSMOS to support above 2 issues. The evaluation objective is different among above 2 issues, and COSMOS has 2 separated modules COSMOS-FP (for at-power) and COSMOS-SD (for shutdown) with the different quantification manners. This paper describes the detailed contents of COSMOS as the risk monitoring tool, and also describes the actual usages of 'At-power risk monitoring in case of On-Line Maintenance' and 'Shutdown risk evaluation for every outage'. (author)