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:
tion of the impact of the proposed licensing basis change on the PRA elements. For applications like component categorization, sensitivity studies on the effects of the proposed licensing basis change may be sufficient. For other applications, it may be DG-1285, Page 27 acceptable to define the qualitative relationship of the impact of the proposed licensing basis change on the PRA elements or to only identify the impacted elements. If the impacts of a proposed licensing basis change to the plant cannot be associated with elements of the PRA, the PRA should be modified accordingly or the impact of the change should be evaluated qualitatively as part of the integrated decisionmaking process discussed in Section C.2.6 of this guide. The assessment should properly account for the effects of the changes on the reliability and unavailability of SSCs or on operator actions. For additional guidance on level of detail for the base PRA, see Regulatory Position C.1.3 in RG 1.200. 2.3.4 Probabilistic Risk Assessment Plant Representation to Support an Application The PRA results used to support an application are derived from a base PRA model that represents the as-built and as-operated plant to the extent needed to support the application. Consequently, the PRA should have been maintained and upgraded, where necessary, to ensure it represents the as-built and as-operated plant. For additional guidance on plant representation for the base PRA, see Regulatory Position C.1.4 in RG 1.200. 2.4 Acceptance Guidelines The risk-acceptance guidelines presented in this RG are based on the principles and expectations for risk-informed regulation discussed in Part C of this RG and are structured as follows. Regions are established in the two planes generated by a measure of the base risk metric (CDF or LERF) along the x- axis, and the change in those metrics (ΔCDF or ΔLERF) along the y-axis (Figures 4 and 5). Acceptance guidelines are established for each region as discussed below. These