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:
to be considered include, but may not be limited to, vibration fatigue, thermal fatigue, corrosion cracking, primary water stress corrosion cracking (PWSCC), IGSCC, microbiologically induced corrosion (MIC), erosion, cavitation, and FAC. Piping segments should be defined taking into account the potential degradation mechanism and the consequence of failure at any point in the segment. Segments with the same consequences but a different degradation mechanism may be combined for consequence characterization, but the development of the inspection program should explicitly address the different degradation mechanisms within such segments. In addition, consideration should be given to identifying distinct segment boundaries at locations of branching points such as flow splits or flow joining points, locations of size changes, isolation valve, motor-operated valves (MOVs) and air-operated valves (AOVs). Distinct segment boundaries should be defined if the break potential is expected to be significantly different for various portions of piping. II.2.2.3 Evaluating Pipe Failures with PRA The licensee’s methodology should systematically use risk insights from the PRA and PRA results to characterize the impact of each segment’s failure on the plant’s risk. The characterization should allow for the determination of the relative safety significance of the different pipe segments and should support the final determination regarding the impact of implementing the program on plant risk. Generally, three or four primary system LOCA sizes and two steam line rupture locations that represent the spectrum of demands on the mitigating systems are modeled in PRAs. An internal events flooding analysis is also included in most PRAs performed in response to Generic Letter 88- 20. Much of this analysis will be used as a basis for determining the consequence of pipe failures. The review should focus on the robustness of the above models and methods in the baseline PRA, as well as