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:
HANGE RISK EVALUATIONS A-1 Other Considerations in Technical Specification Change Risk Evaluations A-1.1 Risk-Informed Measures for Technical Specification Changes to Completion Times and Surveillance Frequencies This section lists the risk-informed measures used in completion time (CT) and surveillance frequency (SF) evaluations.1 NUREG/CR-6141, “Handbook of Methods for Risk-Based Analyses of Technical Specifications,” issued December 1994 (Ref. 1), discusses these measures in more detail. The measures applicable for CT evaluations include the following: a. conditional risk given the limiting condition of operation (LCO), b. incremental conditional core damage probability (ICCDP), and c. yearly CT risk. When comparing the risk of shutting down with the risk of continuing power operation for a given LCO, the following measures apply: a. risk of continued power operation for a given downtime, like ICCDP, and b. risk of shutting down the plant for the same downtime. The following measures apply for SF evaluations: a. test-limited risk, and b. test-caused risk. Similar to the CT evaluations, the risk contributions for preventive maintenance (PM) include the following: a. single PM risk, and b. yearly PM risk. The risk associated with simultaneous outages of multiple components, called configuration risk, is calculated as part of CT changes. The three-tiered approach discussed in Regulatory Position 2.3 of this regulatory guide (RG) includes calculations of risks for multiple components that may be taken down together. The following applicable measures are similar to the CT measures stated above: a. conditional risk (e.g., increase in core damage frequency (CDF)) caused by the configuration, and b. increase in risk (e.g., core damage probability, which is obtained by multiplying 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