Document: NUREG-0800
Document ID: 22c713a3-851c-4195-8d52-e7a90bcbeed0
Document Type: srp
Title: LEAK-BEFORE-BREAK EVALUATION PROCEDURES
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0636/ML063600396.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.6.3
CFR Part: 
CFR Title: 

Content:
reviewer should verify that the licensee’s or applicant’s LBB evaluation uses design basis loads and is based on the as-built piping configuration, as opposed to the design configuration. Correct location of supports and their characteristics (such as gaps) are verified, as are the weights and locations of components such as valves. Particular attention is given to the reliability of snubbers whose failure could invalidate the stresses used in the fracture mechanics evaluations. Compliance with the technical specifications can be used to demonstrate that snubber failure rates are maintained at a low level. 2. The reviewer should evaluate the potential for degradation by erosion, erosion/corrosion, and erosion/cavitation due to unfavorable flow conditions and water chemistry. Industry experience for specific piping systems plays an important role in the evaluation of these degradation mechanisms. Additionally, an evaluation of wall thinning of elbows and other fittings is undertaken to ensure that ASME Code minimum wall requirements are met. These evaluations must demonstrate that these mechanisms are not potential sources of pipe rupture. 3. The review should evaluate the material susceptibility to corrosion, the potential for high residual stresses, and environmental conditions that could lead to degradation by stress corrosion cracking. Primary water stress corrosion cracking (PWSCC) is considered to be an active degradation mechanism in Alloy 600/82/182 materials in pressurized water reactor plants. Alloy 690/52/152 material is not currently considered susceptible to PWSCC for the purposes of LBB application. Industry experience for specific piping systems plays an important role in the evaluation of this degradation mechanism. It is recommended that Alloy 82/182 materials not be used in advanced pressurized water reactor plants and that, if an applicant wishes to use Alloy 82/182, that the applicant address the methods that will be used to mitigate PWSCC.