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:
e viewed online or printed for a fee in the NRC’s Public Document Room (PDR) at 11555 Rockville Pike, Rockville, MD. For problems with ADAMS, contact the PDR staff at 301-415-4737 or (800) 397-4209; fax (301) 415-3548; or e-mail pdr.resource@nrc.gov. RG 1.247, Appendix B, Page B-1 APPENDIX B HAZARDS FOR CONSIDERATION IN A PROBABILISTIC RISK ASSESSMENT A key feature of a probabilistic risk assessment (PRA) is that a wide spectrum of potential hazards in terms of magnitude and frequency of occurrence should be systematically surveyed to ensure that significant contributors to plant risk are not inadvertently excluded. A hazard is a category of similar challenges to plant design or operations that poses some risk to a facility. A hazard group is a set of similar hazards that are assessed in a PRA using common approaches, methods, and likelihood data for characterizing the effect on the plant. Hazards represent events or phenomena that are generally classified as either internal or external, based on the defined plant boundary in a PRA. Hazards categorized under the internal events, internal flood internal fire, seismic, high wind, and external flood hazard groups are typically analyzed and modeled quantitatively using a PRA. However, there are internal and external hazards whose risk to a facility can be assessed qualitatively, quantitatively, or both, but in a simplified manner and without the need for a detailed PRA model. Regulatory Position C.1.3.11 of this regulatory guide (RG) provides additional guidance on screening and conservative analyses used to screen hazards from a detailed PRA. Conversely, some such internal and external hazards may produce impacts on a plant and a potential plant response that are too complex to be represented by a simplified analysis and should be modeled in detail using a PRA. This latter type of hazard is commonly referred to as an “other hazard,” and Regulatory Position C.1.3.14 provides additional guidance on modeling such