Document: NRC Regulatory Guide
Document ID: 4774af39-208c-4761-97e8-2d66c6d14794
Document Type: regulatory_guide
Title: Performance-Based Containment Leak-Test Program (Rev. 1)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2200/ML22006A317.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.163
CFR Part: 
CFR Title: 

Content:
ing ILRT intervals beyond ten years. For the operating reactors that received approval for a one-time, 15-year ILRT interval, no test failures have been reported as of this RG’s issuance. Based upon operating experience, the instances of through-wall corrosion and fatigue degradation of metallic liners and shells that have occurred have been detected by visual examinations under the IWE program, not by ILRTs. Error! Reference source not found. Risk Impact EPRI Report 1009325, “Risk Impact Assessment of Extended Integrated Leak Rate Testing Intervals,” Revision 2-A, issued October 2008 (Ref. 13), provides (1) a generic assessment of the risks associated with a permanent extension of the ILRT surveillance interval to 15 years and (2) a risk informed methodology/template to be used to confirm the risk impact of the ILRT extension on a plant- specific basis. The report uses probabilistic risk assessment (PRA) methods, in combination with ILRT performance data and other considerations, to justify the extension of the ILRT surveillance interval. Plants that rely on containment overpressure for net positive suction head for emergency core coolant system injection for certain accident sequences should address this in the risk assessment, due to the impact on the core damage frequency with the extension of the ILRT interval. In the EPRI PRA model, the failure rates for valves are assumed not to increase with time so that the likelihood of failure is simply proportional to the inspection interval (i.e., it assumes no new modes of failure are introduced). The likelihood of corrosion degradation of the liner is assumed to increase with time of service. The base rate of corrosion failure is based on service experience, and sensitivity studies are used to estimate the impact of increased instances of corrosion failures. In these risk impact assessments, the models that evaluate the change in risk from extending the test intervals are based on the assumption that the effects