Document: NRC Regulatory Guide
Document ID: 47b09be1-4bf8-45f9-a099-7fed871c09bd
Document Type: regulatory_guide
Title: Plant-Specific, Risk-Informed Decisionmaking: Inservice Testing (Rev. 1)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2114/ML21140A055.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.175
CFR Part: 
CFR Title: 

Content:
, the licensee may use information based on engineering analyses and judgment to determine whether a component should be treated as an LSSC or HSSC. One approach to combining these different pieces of information is to use what has been referred to as an expert panel. Appendices B and C to SRP Section 19.2, “Review of Risk Information Used to Support Permanent Plant-Specific Changes to the Licensing Basis: General Guidance,” contain staff expectations on the use of expert panels in integrated decisionmaking and SSC categorization, respectively. RG 1.175, Page 15 In classifying a component not modeled in the PRA as LSSC, the expert panel should determine the following: a. The component does not perform a safety function, does not perform a support function to a safety function, and does not complement a safety function. b. The component does not support operator actions credited in the PRA for either procedural or recovery actions. c. The failure of the component will not result in the eventual occurrence of a PRA initiating event. d. The component is not a part of a system that acts as a barrier to fission product release during severe accidents. e. The failure of the component will not result in unintentional releases of radioactive material even in the absence of severe accident conditions. When using risk importance measures to identify components that are low-risk contributors, the potential limitations of these measures have to be addressed. Therefore, the licensee’s integrated decisionmaking process (e.g., expert panel) should include evaluations that demonstrate the sensitivity of the risk-importance results to the important PRA modeling techniques, assumptions, and data. Issues that the licensee should consider and address when determining low-risk contributors include truncation limit used, different risk metrics (i.e., CDF and LERF), different component failure modes, different maintenance states and plant configurations, multiple component