Document: NRC Regulatory Guide
Document ID: 6f84e3bf-9ff3-49fb-a16a-0de3b89e6bc6
Document Type: regulatory_guide
Title: An Approach for Plant-Specific Risk-Informed Decisionmaking for Inservice Inspection of Piping (Rev. 2)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2103/ML21036A105.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.178
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CFR Title: 

Content:
hether the proposed changes have affected license conditions. A broad review of the licensing requirements and commitments may be necessary because proposed ISI program changes could affect issues not explicitly stated in the licensee’s final safety analysis report or ISI program documentation. The regulation in 10 CFR 50.55a(z)(1) allows the Director of the Office of Nuclear Regulation to authorize alternatives to its specific requirements, provided the proposed alternative will ensure an acceptable level of quality and safety. Thus, licensees may propose alternatives to the acceptable RI-ISI approaches presented in this guide, so long as they provide supporting information that demonstrates that they maintain the key principles discussed in this guide. The licensee should include in its RI-ISI program submittal the exemption requests, alternative request, technical specification amendment requests (if applicable), and relief requests necessary to implement its RI-ISI program. NRC-endorsed ASME Code Cases that apply risk-informed ISI programs are consistent with this RG in that they encourage the use of risk insights in the selection of inspection locations and the use of appropriate and possibly enhanced inspection techniques that are appropriate to the failure mechanisms that contribute most to risk. 2.1.2 Defense-in-Depth Evaluation Defense in depth is an element of the NRC’s safety philosophy that employs successive compensatory measures to prevent accidents or mitigate damage if a malfunction, accident, or naturally caused event occurs at a nuclear facility. The defense-in-depth philosophy has been applied in plant design and operation to provide multiple means to accomplish safety functions and prevent the release of radioactive material. It has been and continues to be an effective way to account for uncertainties in equipment and human performance and, in particular, to account for the potential for unknown and unforeseen failure mechanisms or phenomena