Ductile fracture initiation near axial crack fronts in pressure tubes of hydrided irradiated Zr-2.5Nb materials with split circumferential hydrides

Ductile fracture initiation with consideration of strain concentration and stress triaxiality near axial crack fronts in pressure tube (PT) specimens of hydrided irradiated Zr-2.5Nb materials with split circumferential hydrides is examined by three-dimensional finite element analyses with submodeling. For a PT specimen with split circumferential hydrides, strain concentration occurs in the middle of the ligaments ahead of the crack front. The computational results suggest that only 60-70% of the internal pressure for fracture initiation of an unhydrided irradiated PT specimen is needed to fracture a hydrided irradiated PT specimen with many split circumferential hydrides along the crack front.