Document: NRC Regulatory Guide
Document ID: cde52d5a-adf9-49be-9d1f-59449dfca895
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:
inued validity across different stages. In meeting the technical characteristics and attributes for the seismic portion of an external hazard PRA, a seismic margins method is outside the scope of this RG and would be addressed on a case-by-case basis. C.1.3.11 Hazards Screening Analysis Probabilistic Risk Assessment Element This section identifies the objectives and the characteristics and attributes for a hazards screening analysis for an NLWR PRA that addresses all radiological sources, all POSs, and all levels of PRA analysis. The objective of the hazards screening analysis is to systematically identify all natural and human-caused hazards and, if screening is performed, to adequately justify exclusion of a hazard or hazard group. Screening methods can often be used to show that the contribution of a hazard or hazard group to a risk metric (e.g., radiological doses, health effects to the public) is not significant. Table B-1 in Appendix B to this RG lists the hazards that should be addressed in the PRA. However, to help ensure that analysis resources can be applied to the more important contributors to risk, in many cases, some of the hazards or hazard groups in Table B-1 may be excluded from a detailed PRA if they can be shown to meet predefined and justified screening criteria. For hazards or hazard groups that are screened out from further consideration in a PRA, the justification for screening them out should be archived and may need to be reevaluated in subsequent evaluations, depending on the application, to confirm that the screening remains appropriate. A preliminary screening analysis may be performed to demonstrate that pre-defined qualitative or semi-quantitative screening criteria are met and the hazard or hazard group under consideration can be RG 1.247, Page 37 excluded from further analysis in the PRA. Preliminary screening analyses generally involve more simple and less involved analysis (e.g., demonstrating a hazard or hazard group is not