Document: NUREG-0800
Document ID: 7916b088-fb90-4163-84fe-027bd315bcc5
Document Type: srp
Title: REVIEW OF RISK INFORMATION USED TO SUPPORT PERMANENT PLANT-
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0717/ML071700658.pdf
Revision Date: 2023-06
Chapter: 19
Section ID: 19.2
CFR Part: 
CFR Title: 

Content:
for plants with little operating history the only choice might be the use of generic data. Furthermore, when the impact of the change is being modeled as a modification of parameter values, sufficient plant-specific data may not exist to support the modification. The data-related issues are summarized as follows: (a) if the impact of the application is to be modeled as a change in parameter values associated with basic events representing modes of unavailability of certain SSCs, these changes should be reasonable and should be supported by technical arguments including plant-specific and generic operational information (when available) and (b) the impact of the change should neither be exaggerated nor obscured by the parameter values used for those SSCs unaffected by the change. b. Review Guidance and Procedures 19.2-51 June 2007 It is to be expected that, for a PRA that has undergone a technical review, parameter values will have been judged to be appropriate, whether they have been evaluated using generic or plant-specific data. However, since the review was focused on the PRA as a base case model, a different perspective on the appropriateness of parameter values may be required for specific applications. Therefore, in evaluating PRA applications, reviewers should focus on those parameter values that have the potential to change the conclusions of the analysis. For example, parameters associated with SSCs that appear in the same cutsets or scenarios as the affected SSCs have the potential to distort the conclusions by decreasing the assessed importance of the change if their values are too low, or by increasing it if their values are too high. Similarly, parameters that contribute to the cutsets or scenarios that do not contain affected SSCs can decrease the importance of the change by being too high or increase it by being too low. The failure rates and probabilities used, especially those that directly affect the proposed application, should appropriately