An appropriate crack modeling approach and finite element analysis for stress intensity factors of reactor vessel discontinuities

As a non-replaceable component of nuclear power plants, reactor vessels (RVs) require rigorous integrity assessments. Linear elastic fracture mechanics based on stress intensity factors (SIFs) is widely applied to prevent brittle fractures. With the development of integrated reactors, such as small modular reactors (SMRs), RVs geometries have become more complex, particularly in the transition between the nozzle and the beltline. However, no standardized approach exists for evaluating corner cracks. In this study, three-dimensional finite element (FE) analyses were conducted to investigate transition corner surface cracks in RVs, focusing on the effect of crack orientation and depth for elliptical and circular shapes. Based on the numerical results, a new crack configuration was proposed. The modeling technique and SIF calculations were validated against representative crack configurations reported in the literature and further applied to corner cracks in i-SMR and commercial large-scale operating reactors. This configuration effectively addresses challenges associated with vessel discontinuities and provides a unified framework for crack modeling, enabling more reliable integrity assessments by overcoming the limitations of simplified crack representations used in current procedures.