Document: NRC Regulatory Guide
Document ID: c7a40fcc-fc9d-4eb2-ad86-f9f5b0f04c82
Document Type: regulatory_guide
Title: Plant-Specific, Risk-Informed Decisionmaking:  Technical Specifications (Rev. 2)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1920/ML19206A489.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.177
CFR Part: 
CFR Title: 

Content:
cial aspects of testing to detect failures that occur in a standby period, several adverse effects may be associated with the test that should be considered in the SF evaluation, including downtime to conduct the test, errors of restoration after the test, test-caused transients, and test-caused wear of the equipment. A PRA usually models downtime and errors of restoration, unless they are negligible. Test-caused transients and wear of the equipment are applicable to a few tests but are not generally modeled separately in a PRA. However, they can be evaluated using PRA models supplemented with additional data and analysis. Methods are available to quantitatively address these aspects (Ref. 24); however, qualitative arguments can DG-1287, Page 17 also be presented to support the reduction of an SF. If the adverse impact of testing is considered significant, such cases should be addressed quantitatively. 2.3.5 Sensitivity and Uncertainty Analyses Relating to Assumptions in Technical Specification Change Evaluations As in any risk-informed study, numerous uncertainties about the assumptions made during the PRA model’s development and application can affect risk-informed analyses of TS changes. Sensitivity analyses may be necessary to address the important assumptions in the submittal with respect to TS change analyses. Such sensitivity analyses may include, as appropriate, the following: a. the impact of a variation in repair or maintenance policy because of CT changes (e.g., scheduling preventive maintenance of longer duration at power), b. the impact of variation in assumed mean downtimes or frequencies, c. the effect of separating the cyclic demand versus standby time-related contribution to the component’s unavailability in deciding changes to an SF, d. the effect of details about how CCFs are modeled in the PRA, and e. the effect of modeling compensatory measures in the PRA. Risk resulting from TS CT changes may be relatively insensitive to uncertainties