Walkdown criteria for evaluating seismic margin in nuclear power plants

Research activity in both the Nuclear Regulatory Commission (NRC) and the Electric Power Research Institute (EPRI) to develop criteria to identify the realistic Seismic Margin that exists in nuclear power plants has been under development for the past three years. The overall objective of the EPRI sponsored program is to develop criteria to assess the capability of existing nuclear power plants to safely shutdown in the event of a prespecified larger than design earthquake. An overview of the major steps in conducting a seismic margin assessment (SMA) are presented in a companion paper, Kennedy, (1987). An integral part of the SMA is the plant walkdown which is the topic of this paper.