Maximum allowable crack size for cracks in the attachment weld of nuclear steam generator upper lateral support lugs

Crack indications in the steam generator upper lateral support lug attachment welds were conservatively analyzed using two models: beam-bending model and semi-spherical shell model. In both models, analyses were performed based on the most severe design loadings (Level D loads), including the appropriate ASME structural factors. Linear elastic fracture mechanic (LEFM) with Irwin crack tip plastic zone correction and small scale yielding (SSY) was adopted to establish critical crack sizes. The critical crack sizes were used to dispose of inspected crack indications that exceeded the ASME code Section XI subarticle IWB-3500 acceptance criteria. (author)