Document: NRC Regulatory Guide
Document ID: 82659041-98b0-4721-b25d-c4fb2ea394d0
Document Type: regulatory_guide
Title: An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis (Rev. 3)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1635/ML16358A153.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.174
CFR Part: 
CFR Title: 

Content:
ilistic Risk Assessment Quality” (Ref. 35), when the risk associated with a particular hazard group or operating mode would affect the decision being made, it is the Commission’s policy that, if a staff-endorsed PRA standard exists for that hazard group or operating mode, then the risk should be assessed using a PRA that meets that standard. Section C.2.5 of this guide discusses this further. 2.3.2 Probabilistic Risk Assessment Technical Elements to Support an Application A PRA used in risk-informed regulation should be performed correctly, in a manner that is consistent with accepted practices and commensurate with the scope and level of detail required as discussed in Section 2.3.1 and 2.3.3, respectively, and appropriately represents the plant as discussed in Section 2.3.4. Regulatory Guide 1.200 (Ref. 6) describes one acceptable approach for determining conformance with the technical elements needed in a PRA (in total or the parts that are used to support an application). In general, a PRA that is performed correctly is one where the methods are implemented correctly and the assumptions and approximations are reasonable. The assessment of the risk implications in light of the acceptance guidelines discussed in Section C.2.4 of this guide generally suggests a risk analysis in the form of a PRA. An acceptable PRA is one where the method or approach (1) provides a quantitative assessment of the identified risk in terms of scenarios that result in undesired consequences (e.g., core damage or a large early release) and their frequencies, and (2) is comprised of specific technical elements in performing the quantification. The technical elements are the basic technical analyses that are needed to develop and quantify a PRA model which are defined in the ASME/ANS PRA standard. The specific technical elements can vary depending on the scope of the PRA model, and therefore, as dictated by the application. The ASME/ANS standard provides technical supporting