Document: NRC Regulatory Guide
Document ID: bbd6ed7f-058c-4bd2-8849-f708d0179bbf
Document Type: regulatory_guide
Title: Flexible Mitigation Strategies for Beyond-Design-Basis Events + HISTORY - HISTORY 11/2015 – DG-1301 , Proposed Revision 0
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1316/ML13168A031.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.226
CFR Part: 
CFR Title: 

Content:
equipment that was not included in the ESEP review and is not inherently rugged for seismic accelerations, a licensee should demonstrate that the GMRS level of seismic hazard at the site results in an acceptably low probability of failure. Licensees may rely on the guidance in the American Society of Civil Engineers/Structural Engineering Institute (ASCE/SEI) Standard 43-05, “Seismic Design Criteria for Structures, Systems and Components in Nuclear Facilities” (Ref. 41) related to beyond- design-basis seismic evaluation for purposes of defining an appropriately low probability of failure. ASCE/SEI 43-05 defines a 10% probability of unacceptable performance (C10%) which is reviewed against the beyond-design- basis seismic event (150% of the design-basis event (DBE) ground motion for the ASCE/SEI 43-05 case). The process for calculating the C10% values is defined in this section. Table 1 provides recommended values for βC, βR, βU, and the ratio of the median capacity C50% to the C1% capacity taken from the SPID determined in the EPRI 1025287. The recommended βC values are based on Kennedy’s recommendations in “Overview of Methods for Seismic PRA and Margin Analysis Including Recent Innovations,” Proceedings of the Organization for Economic Co-operation and Development (OECD)-Nuclear Energy Agency (NEA) Workshop on Seismic DG-1301, Page 19 Risk, Tokyo, Japan, August, 1999 (Ref. 42), and on average area biased slightly conservative (i.e., slightly low βC on average). Because random variability βR is primarily due to ground motion variability, a constant βR value of 0.24 is recommended regardless of the SSC being considered. The recommended uncertainty βU values are back-computed from the recommended composite βC and βR values. The β values for Table 1 apply to fragilities tied to ground motion parameters (e.g., PGA or Peak Spectral Acceleration at 5 Hz). The ratios of the 10% failure probability capacity C10% to the C1% capacity have been calculated