Document: NUREG-0800
Document ID: ac43f632-9db1-4857-9f56-bfba45965456
Document Type: srp
Title: * These are modifications to a plant’s design, operations, or other activities that require NRC approval. These modifica
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0232/ML023250195.pdf
Revision Date: 2023-06
Chapter: 19
Section ID: 19
CFR Part: 
CFR Title: 

Content:
insights by using a systematically conservative bias in mission success criteria and that mission success criteria used to justify changes to the plant’s design or operations have a sound technical basis. b. Review Guidance and Procedures When it is determined that the results and conclusions of a risk-informed application are especially sensitive to the choice of mission success criteria, or if the modeling is particularly controversial, reviewers should evaluate the relevant success criteria and the basis for each. SRP 19-A11 If the basis is analytical, it may be appropriate to evaluate the code and the input data used. When it is determined that the computer codes used have not received adequate licensee or other industry review, closer examination of the models should also be considered. The models, codes, and inputs used to determine mission success criteria should meet QA standards that are consistent with generally accepted methods. Standards should include configuration control of the analysis inputs and results. The standards do not have to be the same as the standards applicable to SAR analysis, but they should be explicit (i.e., engineering calculations and codes should be verified and quality assured) and they should be formalized as part of the licensee’s QA program. In cases where the basis for the success criteria is lacking, reviewers should either request additional licensee justification or seek independent analysis. Licensee justification could include the use of alternative plausible models to justify the conclusions (thus addressing the model uncertainty) or the redesign of the change such that the change is not affected by the choice of success criteria. Some mission success criteria can validly be extrapolated between similar plants when a firm basis for the criteria is created at the first plant and when the licensee shows that plant-specific features do not invalidate the comparison. On an application-specific basis, reviewers should