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:
ltiplying the increase in CDF by the duration of the configuration for the occurrence of a given configuration). 1 The improved Standard Technical Specifications (NUREGs 1430–1434) use “completion time” and “surveillance frequency” in place of “allowed outage time” and “surveillance test interval.” DG-1287, Appendix A, Page A-2 If different measures are used, the licensee should provide adequate discussions of them in its submittal. A-1.2 Measures for Multiple Technical Specification Changes When multiple technical specification (TS) changes are being considered, the combined impact of the individual changes should also be considered. The following sections discuss the considerations related to the calculation of total impacts. A-1.2.1 Measures That Can Be Combined for Multiple Technical Specification Changes When considering risk contributions from several CTs, the risk measures can be combined according to the following guidelines: a. The ICCDPs from several CTs do not generally interact nor accumulate to give a total contribution because the single CT risks are conditional risks per event, and the downtime events for the different CTs are different events. The only time that ICCDPs should be considered simultaneously is when multiple components can be down at the same time, constituting the same event. Such a case is referred to as a “downed configuration,” or simply a “configuration.” The risk contribution associated with a configuration is referred to as the configuration risk and is evaluated separately as a multiple component downtime. Conducting maintenance on several components is a principal cause of potentially high configuration risks. b. Yearly CT risk contributions from several CTs can interact and should be accumulated to give the total yearly contribution from all the CTs being considered. When the CTs do not interact (i.e., when the downed components are not in the same minimal cutset), the yearly CT risk contribution from