EPRI Pilot Application of the ASME/ANS Seismic PRA Standard

December 30, 2011
Publication: International Topical Meeting on Probabilistic Safety Assessment and Analysis 2011, PSA 2011, American Nuclear Society
Author(s): Gregory Hardy Robert Kassawara Divakar Bhargava David Moore

The American Society of Mechanical Engineers (ASME) and the American Nuclear Society (ANS) have developed a "Standard for Level 1/Large Early Release Frequency Probabilistic Risk Assessment for Nuclear Power Plant Applications." The objective of the Standard is to provide basic requirements for performing probabilistic risk assessments that would support future risk informed decisions. The Standard limits its requirements to performing a Level 1 analysis of the core damage frequency (CDF) and a limited Level 2 analysis of Large Early Release Frequency (LERF). The Standard also provides requirements for a graded approach to risk assessment. These requirements are set for three "Capability Categories" representing three levels of detail. Guidance is not provided as to which capability category is appropriate for risk-informed decisions. This is left to the judgment of the risk analyst. The probabilistic risk assessment (PRA) standards for internal events and for fire have been piloted and updated in past studies and are further along in terms of common usage, regulatory review, and familiarity by nuclear industry engineers than is the case for seismic risk. While seismic PRAs (SPRAs) have been conducted for research purposes and in response to the Individual Plant Evaluation for External Events (IPEEE), no systematic SPRA has been conducted using the new SPRA standard requirements. Dominion Generation teamed with Electric Power Research Institute (EPRI) to conduct this Pilot study of the Surry nuclear plant. The purpose of the EPRI pilot project was twofold: To evaluate the process, requirements, and results involved in updating the Surry SPRA developed for the IPEEE program using modern SPRA methods such that it can meet regulatory approval and be used in future risk-based decision making [and] To review the requirements in the ASME/ANS SPRA Standard to determine if they are reasonable or require clarification relative to the current state of the art in performing SPRAs. This paper focuses on the keyresults from this SPRA Pilot project.

Markets: Nuclear