Regulatory uses of PRA/PSA by the USNRC

Probabilistic Risk Assessment is finding increasing acceptance by the U.S. Nuclear Regulatory Commission and is extensively applied in a number of safety assessments and regulatory activities. Specific issues highlighted and evaluated in this paper include safety issue prioritization and the issues of station blackout and containment leaktightness. PRA techniques and insights are also finding extensive usage in addressing the severe accident issue for nuclear power plants. Included in this are the development of methods and guidelines for individual plant examinations for severe accident vulnerabilities, the evaluation of the relative importance of containment failure modes from severe core melt accidents, and the development of mitigation strategies and fixes to enhance containment effectiveness against severe accidents. (orig.)