Document: NRC Regulatory Guide
Document ID: 8a2332d3-66ca-40af-84e1-507db8b26559
Document Type: regulatory_guide
Title: TRIAL - Acceptability of Probabilistic Risk Assessment Results for Non-Light Water Reactor Risk-Informed Activities
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2123/ML21235A008.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.247
CFR Part: 
CFR Title: 

Content:
cation SPECIFY the basis for screening of inherently rugged RG 1.247, Appendix A, Page A-39 Table A-11. Staff Position on ASME/ANS RA-S-1.4-2021, Technical Requirements for Seismic PRA Index No. Issue Position Resolution earthquake experience and data from operating light- water reactors. Nonlight-water reactors can have SSCs that differ in form and design from light-water SSCs. This may result in either these SSCs not being covered by the current inherently rugged component groups or demonstrating that these SSCs are similar to a particular current inherently rugged component group. Further, the bounding site or range of sites can have a seismic hazard exceeding that used to develop the current inherently rugged component list. Therefore, use of the inherently rugged component groups based on LWRs needs justification and the basis for screening of inherently rugged components needs to be specified. Inappropriate screening of inherently rugged components may result in their exclusion from a seismic PRA and/or in an underestimation of risk. components justifying the applicability to the plant. RG 1.247, Appendix A, Page A-40 Table A-11. Staff Position on ASME/ANS RA-S-1.4-2021, Technical Requirements for Seismic PRA Index No. Issue Position Resolution SFR-C2 The methodologies and approaches for determining the fragility thresholds is based on operating light-water reactor seismic risk and seismic PRA experience (e.g., generic lognormal uncertainty parameters dependent on type or location of SSC, relative contribution to total seismic risk of assuming that a failure leads directly to core damage).These state- of-practice methodologies and approaches may not be applicable to nonlight-water designs or their applicability may need a design- specific technical basis. Further, the same threshold may not be applicable to a range of sites and, for such cases, use of a single threshold would need justification. Inappropriate fragility thresholds may result in inadvertent