Document: NUREG-0800
Document ID: d5452e7b-1e61-498b-9e3d-71073b3328ef
Document Type: srp
Title: LEAK-BEFORE-BREAK EVALUATION PROCEDURES
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0302/ML030280295.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.6.3
CFR Part: 
CFR Title: 

Content:
e to brittle cleavage-type failure over the full range of system operating temperatures (that is, the material is on the upper shelf). 9. The reviewer determines that the system(s) under evaluation do not have a history of fatigue cracking or failure. An evaluation is performed to assure that the potential for pipe rupture due to thermal and mechanical induced fatigue is unlikely. Licensees and applicants must demonstrate that there is adeauate mixing of high and low temperature fluids so that there is no potential for significant cyclic thermal stresses. In add ition, it must also be demonstrated that there is no significant potential for vibration induced fatigue cracking or failure. 10. The following steps constitute an acceptable deterministic leak-before break evaluation procedure: a. Demonstrate the accuracy of both the fracture mechanics and the leak rate computational methods by comparison with other acceptable computational procedures or with experimental data. b. Identify the types of materials and materials specifications used for base metal, weldments and safe ends, and provide the materials properties including toughness and tensile data, long-term effects such as thermal aging, and other limitations. 3.6.3-a c. Specify the type and magnitude of the loads applied (forces, bending and torsional moments), their source(s) and method of combination. For each pipe size in the functional system, identify the location(s) which" have the least favorable combination of stress and material properties for base metal, weldments and safe ends. d. Postulate a throughwall flaw at the location(s) specified in (c.) above. The size of the flaw should be large enough so that the leakage is assured of detection with the margin specified in 111.3 above using the installed leak detection capability when the pipes are subjected to normal operating loads. If auxiliary leak detection systems are relied on, they should be described. For the estimation of leakage, the normal