Experience with PRA applications in Ontario Hydro Nuclear

Ontario Hydro has carried out probabilistic risk assessments (PRAs) for a number of its nuclear generating stations, comprising detailed fault tree models of various safety-related plant systems, component failure data bases, and in-plant and ex-plant consequences of severe accidents. The PRA s have frequently been used to support plant operation in areas such as assessment of safety impact of forced equipment outages, maintenance planning, prioritization of systems and components for resource allocation, and reliability assessments of design backfits. This paper provides details of a number of such applications. For each application it describes the issues of concern, the evaluation method, and the manner in which PRA results were used in issue resolution. (author)