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:
he application. Review plant operating history for initiating events that might have been prevented by the proposed application. Review plant operating history for failures of mitigating system trains attributable to events that might have been prevented by the proposed application. SRP 19-B3 Review accident sequence modeling for instances in which early termination of the analysis obscured challenges to affected SSCs that would normally come into play later than the terrriination point. Possible dispositions of the above tasks include the following results: The item will not affect initiating event frequency or mitigating system performance under reasonably foreseeable circumstances, and the proposed change is warranted. Although unmodeled, the item already receives and will continue to receive programmatic attention commensurate with its significance. In cases where reduced commitments are proposed, adequate justification is provided for this reduction. The item does not currently receive sufficient programmatic attention, and may be subject to tighter controls. Reviewers should verify that the safety significance of SSCs not modeled in the PRA (but affected by the proposed application) are appropriately characterized and justified. Addressing limitations of: the risk analysis One objective of the integrated decisionmaking process is to overcome certain limitations of the PRA. However, this does not include substituting the analyst's judgment for essential PRA results. One reason for developing PRA models is that the complexity of many facilities makes judgment difficult in many contexts. Generally, if the PRA highlights a plant vulnerability, this should be taken seriously and should not be discounted on the basis of judgment. If the analyst can show that the PRA representation of a vulnerability is invalid, then the PRA should be modified, and the licensee should work wilt the results of the revised PRA. To address the issue of credit for unmodeled systems that