Document: NUREG-0800
Document ID: fe8ec6c2-e960-404c-854f-55c77bde1672
Document Type: srp
Title: NUREG-0800
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML2400/ML24005A077.pdf
Revision Date: 2024-05
Chapter: 7
Section ID: 7
CFR Part: 
CFR Title: 

Content:
at the impact of the CCF on plant equipment, functions, and operator actions not modeled in the PRA is not risk significant. f. Key assumptions and sources of uncertainty affecting the application are identified and dispositioned following established guidance such as RG 1.200 or equivalent guidance for new reactors, as well as NUREG-1855, Revision 1, “Guidance on the Treatment of Uncertainties Associated with PRAs in Risk-Informed Decisionmaking,” issued March 2017. 3.4.3 Determining the Risk Significance of Common-Cause Failures The risk significance of a CCF can be determined using a bounding sensitivity analysis that assumes the probability of the CCF is 1 or a sensitivity analysis that uses a conservative value less than 1 for the probability of the CCF. In some situations (e.g., for a CCF associated with an upgrade from analog to digital control room annunciators), a CCF may not disable a protective function, but it may affect operators’ ability to perform required actions. In these situations, the risk significance of the CCF can be determined by modeling the operators’ failure to perform required actions and conducting either BTP 7-19-33 Revision 9 — May 2024 a bounding sensitivity analysis (assuming a probability of 1) or recalculating the applicable human error probabilities, with supporting technical justification for the recalculated values (e.g., if there are other indicators present that will allow operators to detect and diagnose the plant status). Acceptance Criteria for Determining the Risk Significance of Common-Cause Failures If the application meets the following acceptance criteria, which are to be used in conjunction with the information in the application related to the principles of risk-informed decision-making in RG 1.174, the reviewer should conclude that the application provides sufficient information on determining the risk significance of the CCF: a. If the increase in risk from the CCF is calculated using a bounding