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:
ning and conservative analyses that can be performed to this end. Conversely, some such internal and external hazards may produce impacts to 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.1.2.9 in Section C of this RG provides additional guidance on the modeling of such hazards. A minimum list of hazards and their potential impacts that should be considered are listed below in Tables D-1 and D-2 below. Table D-1 provides an extensive list and general description of the hazard groups and the hazards within those groups that should be considered during the development of a base PRA. The genesis of this list can be traced back to NUREG\CR-2300, “PRA Procedures Guide” (Ref. 1), and earlier nuclear power plant PRA studies. This list of hazards has evolved and expanded over the past several decades based on insights and lessons learned from other PRA-related programs and applications such as licensees’ responses to Generic Letter 88-20 (Ref. 2). Table D-2 provides a list of hazard causes and potential conditions to consider during the process of determining whether a given hazard poses some risk to a facility. The taxonomy of these hazard groups and the hazards within those groups are relevant to PRA applications only. Table D-1. List of Hazards Hazard Group/ Hazard Direct or Secondary Impact of Hazard INTERNAL HAZARDS Internal Events Failures of structures, systems, and components (SSCs) and human errors internal to the defined plant boundary. Hazards that are typically analyzed in this hazard group include, but are not limited to loss-of-coolant accidents, loss of offsite power, plant transient, loss of condenser heat sink, etc. Internal Flood Flooding that results from leaks or ruptures of liquid systems (e.g., tanks, pipes, valves, pumps) originating inside the