This study was performed to define the seismic loading conditions for use in the crack stability assessment of a BWR for the applicability of the leak-before-break (LBB) criterion. The LBB has been applied to the design of Class-1 piping in Japanese light-water reactors. Crack propagation in the LBB applicability review is classified into the Level C service condition. Here an S1-earthquake (maximum design earthquake) is currently assumed, rather than an S2-earthquake (extreme design earthquake). In order to justify this assumption, the frequency of an S1-earthquake occurring during coolant leakage due to crack propagation was determined. The frequency of coolant leakage from Class-1 piping must be less than that of the Level C service condition (2.5×10−2 to 1×10−4 per year) in order to assume that an S1-earthquake is appropriate. Accordingly, the frequency of coolant leakage from Class-1 piping was calculated using a probabilistic fracture mechanics (PFM). The results of this analysis indicate that the frequency of coolant leakage from Class-1 piping is less than the expected occurrence of the Level C service condition. As the results, it is concluded that the assumption of the seismic loading employed in an LBB applicability review should be appropriate.
Seismic Loads for Crack Stability Assessment in a Review of Lead-Before-Break (LBB) Applicability
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Yamashita, N, Machida, H, Yoshimura, S, & Yagawa, G. "Seismic Loads for Crack Stability Assessment in a Review of Lead-Before-Break (LBB) Applicability." Proceedings of the ASME/JSME 2004 Pressure Vessels and Piping Conference. Pressure Vessel and Piping Codes and Standards. San Diego, California, USA. July 25–29, 2004. pp. 365-372. ASME. https://doi.org/10.1115/PVP2004-2714
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