Document: NUREG-0800
Document ID: e32f0820-4e33-476e-aa36-4ca8c2c64af0
Document Type: srp
Title: Use of Probabilistic Risk Assessment in Plant-Specific, Risk-Informed Decisionmaking:
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0119/ML011940192.pdf
Revision Date: 2023-06
Chapter: 19
Section ID: 19.0
CFR Part: 
CFR Title: 

Content:
used for the current application should already model the effects of past applications. However, qualitative and synergistic effects are sometimes difficult to model in the PRA. Therefore, a review of changes in risk (both quantifiable and non-quantifiable) from previously submitted changes to the plant's design and operation would provide a means to account for the cumulative and synergistic effects of these changes. For all previous changes, reviewers should consider the following factors: the calculated change in risk for each application (CDF and LERF) and the plant elements (SSCs, procedures, etc.) affected by each change qualitative arguments used to justify the change (if any) and the plant elements affected by those arguments compensatory measures or other commitments used to help justify the change (if any) and the plant elements affected a summary of the results from the monitoring programs (where applicable) and a discussion on how these results have been factored into the PRA or into the current application the plant risk profile to ensure that the accumulation of changes has not created dominant risk contributors SRP 19-23 If the licensee's submitt:al includes past changes made to the plant (but not submitted to the NRC) that reduced tihe plant risk, especially changes related to the current application, reviewers should consider such changes in the integrated decisionmaking process. Benefits from the implementation of the Maintenance Rule can also be credited for the applicable SSCs. Beyond cumulative effects, synergistic effects are also possible, and some of these might not emerge from a quantification of the PRA. For example, if conventional importance ranking approaches are employed to determine the importance of SSCs, it would be possible that multiple requirements could be relaxed on certain "low" significant components under multiple applications. If the QA (potentially affecting the failure rate) and the test interval (potentially affecting