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:
ic of the PRA that affects the application. The staff review could also involve performing (or reviewing) sensitivity studies where the truncation limit is lowered for the dominant sequences and event initiators, as well as studying the resultant cutsets or scenarios to see if there are any hidden dependencies or unusual/unexpected event combinations (especially if these involve components affected by the proposed application). Reviewers could also include comparing a list of the events affected by the application that is in the final truncated cutset equations to the list of application-specific basic events used in the fault tree and event tree models. This yields a list of events that did not make it pass the truncation process. Documentation should be available to enable reviewers to determine the reason truncated events are not important to risk. Finally, in PRA models where common cause failures and human dependencies are incorporated at the sequence level after a truncated set of minimal cutsets has been obtained, reviewers should verify that the truncation criteria used in the PRA do not lead to cutsets involving application-specific components being truncated that could be important if common cause failures or human dependencies are considered. c. Evaluation Findings Reviewers should verify that the information provided and review activities conducted support the following conclusions: • The change is appropriately modeled and is properly quantified. • The licensee has satisfactorily established that conclusions are not adversely affected by truncation either because (i) the change in risk from the application was calculated by the requantification of the base model, or (ii) if model requantification was not performed, or if the application depended on the risk ranking of SSCs from a pre-solved cutset equation, the following apply: < The truncation criterion is sufficiently low to ensure stable results, that is, the magnitude of the CDF or release