Document: NRC Regulatory Guide
Document ID: 22ccfd5e-c5d8-4615-a02c-32369aa9f533
Document Type: regulatory_guide
Title: Acceptability of Probabilistic Risk Assessment Results for Risk-Informed Activities (Rev. 3)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1930/ML19308B636.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.200
CFR Part: 
CFR Title: 

Content:
------------- No objection -------------------- Table 5-2.2-1 HLR-SFR-A through HLR-SFR-F -------------------- No objection -------------------- Table 5-2.2-2 Introductory text -------------------- No objection -------------------- SFR-A1 The intent of supporting requirement SFR-A1 Clarification The NMA already discusses the overall intent of SFR-A1 and distinguishes between failure mechanism and failure DG-1362, Appendix B, Page B-12 Table B-1. Staff Position on ASME/ANS RA-S Case 1, “Case for ASME/ANS RA-Sb-2013 Standard for Level 1/Large Early Release Frequency Probabilistic Risk Assessment of Nuclear Power Plant Applications,” Technical and Peer Review Requirements of a Level 1, Seismic PRA for the At-Power Operating Mode Index No Issue Position Resolution needs additional clarification. mode. Include in the NMA a discussion such as: The intent of SFR-A1 is to ensure that the fragility analyst provides fragility assessments for the SSCs defined by the systems analyst in the plant’s SEL and for the relevant failure modes associated to the basic PRA events. The understanding is that fragility assessments relate to failure mechanisms, which, in turn, relate to failure modes defined by the systems analyst. SFR-A2 The information to be included should be such that it can justify the modeling of SSCs as correlated from a fragility perspective and not simply be relevant. Justification, more than the examples provided, will be necessary for any correlation other than 0 and 1. Additionally the phrase “fragility correlation” should be replaced with “fragility dependence”. Dependence between random variables characterize their interrelationship. Correlation (coefficient) is used to define the dependence structure between random variables. It is also lacking criteria for determining the acceptability of a correlation model. Clarification INCLUDE information relevant to justifying the modeling of fragility dependency correlation of SSCs and its basis (e.g.,