Document: NUREG-0800
Document ID: 8dd882f4-a34f-4415-acd1-ebb441c72786
Document Type: srp
Title: PROBABILISTIC RISK ASSESSMENT AND SEVERE ACCIDENT
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1213/ML12132A481.pdf
Revision Date: 2023-06
Chapter: 19
Section ID: 19.0
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Content:
effects, should they occur. In particular, the SRM on SECY-93-087 provides direction about the treatment of external events in PRAs to support DC and COL applications. Specifically: 1. The Commission approved the use of 1.67 times the design-basis SSE for a margin-type assessment of seismic events. 2. The Commission approved the use of PRA insights to support a margins-type assessment of seismic events. A PRA-based SMA will consider sequence-level HCLPF and fragilities for all sequences leading to core damage or containment failures up to approximately one and two thirds the ground motion acceleration of the Design-Basis SSE. 19.0-11 Draft Revision 3 – September 2012 3. The Commission approved the use of simplified probabilistic methods, such as but not limited to the Electric Power Research Institute (EPRI) Fire-Induced Vulnerability Evaluation (FIVE) methodology, to evaluate fire risk. 4. The Commission approved the staff’s position that advanced LWR vendors should perform bounding analyses of site-specific external events likely to be a challenge to the plant (such as river flooding, storm surge, tsunami, volcanism, high winds, and hurricanes). When a site is chosen, its characteristics should be compared to those assumed in the bounding analyses to ensure that the site is enveloped. If the site is enveloped, the COL applicant need not perform further PRA evaluations for these external events. The COL applicant should perform site-specific PRA evaluations to address any site-specific hazards for which a bounding analysis was not performed or which are not enveloped by the bounding analyses to ensure that no vulnerabilities due to siting exist. In addition, Regulatory Issue Summary (RIS) 07-06, “Regulatory Guide 1.200 Implementation,” dated March 22, 2007, states that PRAs required under 10 CFR Part 52 should use NRC- endorsed consensus standards to the extent practicable. Acceptance Criteria Based on these guidance documents and the major objectives