Flaw evaluation

In the case of the ASME codes for nuclear pressurised components, the questions of fatigue design and of flaw evaluation are dealt with separately in ASME Section III and Section XI Appendix A, respectively. The design S-A curve for machined butt welds typical of thick section pressurised components is set at a factor of two on stress range or twenty on cyclic life, whichever is more conservative, below the mean of S-N data developed on smooth cylindrical specimens in air. (A somewhat similar design curve obtained by a different method from experimental S-A data for machined butt welds is given in British Standard 5500.) These safety factors are intended to encompass any adverse influence of minor weld defects, size effects, data scatter and environment. As far as environmental effects are... 

Marston T U (ed.) (1978), Flaw Evaluation Procedures ASME Section XI, EPRI NP 719 SR, Special Report, August, Electric Power Research Institute, Palo Alto, CA. 

The BWRVIP has developed guidelines [6.33] for inspection and flaw evaluation of core plates. 

The BWR VIP has developed guidelines [6.34] for inspection and flaw evaluation of core spray internal that can be followed in the place of prior GE SILs and replace the requirements of NRC Bulletin 80-13 [6.3]. The inspection guidelines present a baseline approach for the first inspection for each plant to new BWRVIP requirements. The inspection can be visual or UT. Tracking of susceptibility trends may provide a rationale for changing reinspection frequencies as further inspection data accumulates. 

The BWRVIP flaw evaluation guidelines recommend loading combinations for plants that do not have such information in plant documentation. Methodology is provided to take stresses from finite element analyses of the core spray system under these loading combinations and to perform limit load flaw evaluation at each weld. 

BWR Vessel and Internals Project, BWR Core Plate Inspection and Flaw Evaluation Guidelines (BWRVIP-25), EPRI Report TR-107284, December 1996. 

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