Industry approach to seismic severe accident policy implementation

The Nuclear Regulatory Commission (NRC) issued a severe reactor accident policy for existing plants on August 8, 1985 which describes the formal basis by which the NRC intends to resolve issues related to potential severe reactor accidents. Examination of plant-specific vulnerabilities due to seismic and other externally initiated events was considered on a later schedule and is addressed in Supplement 4 of the NRC Generic Letter No. 88-20 and a NRC guidance document, NUREG-1407, issued in June 1991. This report was prepared to provide a coherent and effective approach for seismic severe accident review which meets the intent of Generic Letter No. 88-20, Supplement 4. The recommendations in this report provide guidance on plant review types and review implementations which is consistent with the ''limited-scope'' intent of systematic evaluations as described in the NRC's Severe Accident Policy Statement. In addition, to assist in implementing cost-effective modifications that reduce vulnerabilities, this report also presents specific guidelines for identification and treatment of vulnerabilities that may be used as a basis for defining closure of earthquake-related severe-accident issues. This report provides procedural instructions and guidance to support resolution of earthquake-related severe accident issues. More detailed background and technical justifications for the methods are documented elsewhere, and are referenced throughout this report as appropriate