Document: NUREG-0800
Document ID: b07c8dd1-23f6-41f1-a3ba-aa378f9ea59a
Document Type: srp
Title: RISK-INFORMED INSERVICE INSPECTION
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0325/ML032510135.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.9.8
CFR Part: 
CFR Title: 

Content:
th PRA Pipe ruptures are traditionally modeled as initiators, and the failure of individual pipe segments or structural elements is not modeled in PRAs. The manner in which PRA, or the PRA results, is modified so that a more detailed treatment of the potential (or probability) of pipe failures and the influence of such failures on other systems is incorporated in the PRA is reviewed. I.2.2.4 Piping Failure Potential Segment failure potential may be a quantitative estimate for each segment, or segments may be categorized into groups based on similar degradation mechanism, environment, and failure modes. There are three failure modes: 1. Initiating event failures in which the failure directly causes a transient and may or may not also fail one or more plant trains or systems. Initiating event failures are characterized by failure frequency. 2. Standby failures are failures that cause the loss of a train or system but do not directly cause a transient. Standby failures are characterized by train or system unavailability for which shutdown may be required by technical specifications or limiting conditions for operation. Unavailability is a combination of failure frequency and exposure time. 3. Demand failures are failures accompanying a demand for a train or system and are usually caused by the transient induced loads on the segment during system startup. Demand failures are characterized by a probability per demand. The approach used for the determination of failure potential of piping segments is reviewed. The manner in which past failure data, expert opinion, and probabilistic fracture mechanics is considered in determining the piping failure potential is reviewed. The determination of exposure time appropriate to standby failures is reviewed. It is expected that inspections will be performed in 3.9.8-5 accordance with the schedule of Inspection Program A or Program B as specified in ASME B&PVC Section XI. When data analysis is utilized, appropriateness and