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
CFR Part: 
CFR Title: 

Content:
rimary system piping as having low safety significance and calculated that, with no inspections, the frequency of leaks would not increase beyond existing performance history of the ASME BPV Code, the staff would continue to require some level of nondestructive examination inspection. 2.1.3 Safety Margins In engineering programs that affect public health and safety, safety margins are applied to the design and operation of a system. These safety margins and accompanying engineering assumptions are intended to account for uncertainties, but in some cases, they can lead to operational and design constraints that are excessive and costly, or that could detract from safety (e.g., result in unnecessary radiation exposure to plant personnel). Insufficient safety margins may require additional attention. Before requesting relaxation of the existing requirements, the licensee must ensure that the uncertainties are adequately addressed. The quantification of uncertainties would likely require supporting sensitivity analyses. The engineering analyses should address whether the impacts of the changes proposed to the ISI program are consistent with the key principle that adequate safety margins are maintained. The licensee is expected to select the method of engineering analysis appropriate for evaluating whether sufficient safety margins would be maintained if the proposed change were implemented. An acceptable set of guidelines for making that assessment is summarized below. Other equivalent decision criteria could also be found acceptable. Sufficient safety margins are maintained when both of the following occurs: a. Codes and standards or alternatives approved for use by the NRC are met. (See section C.2.1.1.) b. Safety analysis acceptance criteria in the licensing basis (e.g., updated final safety analysis report, supporting analyses) are met, or proposed revisions provide sufficient margins to account for analysis and data uncertainty. 2.1.4 Piping Segments A systematic