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:
h material category as follows. (vii) Base Metal and TIG Welds: The flow stress used to construct the master curve is expressed as f y u ó = 0.5 ( ó + ó ), y u when the yield strength, ó , and the ultimate strength, ó , at temperature are known. If the yield and ultimate strengths at temperature are not known, then ASME Code minimum values at temperature can be used, or alternatively f if (SI) / 17 M < 2.5, then ó = 51 ksi, or 3.6.3-11 Revision 1 - March 2007 y If (SI) / 17 M > 2.5, then ó = 45 ksi. The value of SI used to plot the master curve for base metal and gas tungsten arc welds is m b SI = M (P + P ), (7) where b P = the combined primary bending stress, including deadweight and seismic components. (viii) Shielded Metal Arc (SMAW) and Submerged Arc (SAW) Welds: The flow stress used to construct the master curve must be 51 ksi. The value of SI used to plot the master curve for SMAW and SAW is m b e SI = M (P + P + P ) Z, (8) where e P = combined expansion stress at normal operation, Z = 1.15 [1.0 + 0.013 (OD-4)] for SMAW, (9) Z = 1.30 [1.0 + 0.010 (OD-4)] for SAW, (10) OD = pipe outer diameter in inches. When the allowable flaw length is determined from the master curve at the appropriate SI value, it can be used to determine if the required margins on load and flaw size are met using the following procedure: For an absolute sum load combination method, margin, M, is set to 1.0. If the allowable flaw length from the master curve is equal to at least twice the leakage size flaw, the margins on load and flaw size are met. For the algebraic sum method of load combination, set margin M to 1.4 initially. If the allowable flaw length from the master curve is at least equal to the leakage size flaw, then the margin on load is met. Second, let M = 1.0 and if the allowable flaw length from the master curve is at least twice the leakage size flaw, then the margin on flaw size is met. Additional guidance on the fracture mechanics evaluation can be found in NUREG-