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:
rized as HSSC (e.g., less frequent or informative tests). In some situations, an acceptable test strategy for components categorized as HSSC may be to conduct the existing approved OM Code IST test at the prescribed frequency. In some situations, an acceptable test strategy for components categorized as LSSC may be to conduct the existing approved OM Code IST test at an extended interval. NRC-approved ASME risk-informed Code Cases may define an acceptable strategy for testing components categorized as HSSC and LSSC. Licensees that choose to pursue RI-IST programs should consider adopting ASME-developed and NRC-approved test strategies and should justify deviations from approved ASME Code Cases as part of the RI-IST program request. In establishing the test strategy for components, the licensee should consider component design, service condition, and performance, as well as risk insights. The proposed test strategy should be supported by data that are appropriate for the component. The omission of either generic or plant-specific data should be justified. The proposed test interval should be significantly less than the PRA-assumed expected time to failure of the components in question (e.g., an order of magnitude less). For example, the motor-operated valve (MOV) exercise requirement (which is comparable to the current stroke time test) should be performed at intervals considerably shorter than the expected time to failure. In addition, the licensee should demonstrate that adequate component capability (margin) exists, above that required during design basis conditions, such that component operating characteristics over time do not result in reaching a point of insufficient margin before the next scheduled test activity. The IST interval should generally not be extended beyond once every 6 years or three refueling outages (whichever is longer) without specific, compelling, documented justification. Extensions beyond 6 years or three refueling outages (whichever is