Reliability Data Required for a Seismic Risk Assessment

Abstract

The seismic risk methodology developed in the Seismic Safety Margins Research Program (SSMRP) [1] was demonstrated by its application to the Zion nuclear power plant [2], a pressurized water reactor (PWR). A detailed model of Zion, including plant logic models (initiating events, events trees, and fault trees), SSI and structure models, and piping models, was developed and analyzed. At the request of the U.S. Nuclear Regulatory Commission, the Lawrence Livermore National Laboratory (LLNL) developed a simplified seismic risk assessment methodology [3]. The purpose of this methodology is to reduce cost while adequately assessing the seismic risk from a nuclear power plant. The simplified methodology was used to assess the seismic risk from the Zion nuclear power plant. These results were then compared with the results from the detailed analysis. It was found that the simplified method generally provides more conservative results than the detailed one. To demonstrate its applicability, and to provide a basis of comparison of seismic risk between a PWR and a BWR when analyzed with comparable methodology and assumptions, a seismic risk analysis is being performed on the LaSalle County Station nuclear power plant.