Risk reduction analysis of severe accident prevention and mitigation systems

The Nuclear Regulatory Commission (NRC) is currently addressing the problem of how regulations might be changed to include consideration of degraded core accidents. In support of this, the Severe Accident Risk Reduction program is being performed to assess the benefits and impacts of a set of degraded core safety features. This paper describes some initial results of Phase I of the program which includes estimates of the effects which various preventive and mitigative safety features have on the frequencies and consequences of core melt accidents for six reference reactors