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:
applications. Optimally, the PRA used for the current application should already model the effects of past applications. However, qualitative effects and synergistic effects are sometimes difficult to model. Tracking changes in risk (both quantifiable and nonquantifiable) that are due to plant changes would provide a mechanism to account for the cumulative and synergistic effects of these plant changes and would help to demonstrate that the proposing licensee has a risk management philosophy in which PRA is not just used to systematically increase risk, but is also used to help reduce risk where appropriate and where it is shown to be cost effective. The tracking of cumulative risk also helps the NRC staff in monitoring trends. DG-1285, Page 44 As part of the submittal, the licensee should track and submit the impact of all plant changes that have been submitted for NRC review and approval which have not yet been incorporated into the base PRA model, and are therefore not reflected in the base risk. Documentation should include the following: • the calculated change in risk for each application (CDF and LERF) and the plant elements (e.g., SSCs, procedures) affected by each change, • qualitative arguments used to justify the change (if any) and the plant elements affected by these arguments, • compensatory measures or other commitments used to help justify the change (if any) and the plant elements affected, and • summarized results from the monitoring programs (where applicable) and a discussion of how these results have been factored into the PRA or into the current application. As an option, the submittal could also list (but not submit to the NRC) past changes to the plant that reduced the plant risk, especially those changes that are related to the current application. A discussion of whether these changes are already included in the base PRA model should also be included. DG-1285, Page 45 D. IMPLEMENTATION The purpose of this section is to provide