Experimental verification of the feasibility of crack arresting in the WWER-440 reactor pressure vessel material

Three cross-shaped specimens were subjected to testing in conditions simulating a pressurized thermal shock. Out-of-plane stress was present in addition to opening stress. The specimen contained a fatigue cyclized crack and relieving cracks serving to achieve uniform stress intensity factor patterns along the crack front. The specimens were stressed by 8-point bending. The experiments gave evidence that the possibility of arresting the unstable crack propagation also exists in the isothermal experiment with biaxially loaded cross specimens, and that the fracture toughness values of the 15Kh2MFA steel in the arrested crack condition exhibit a rather small dispersion: the lower estimate at temperatures about -70 deg C is about 30 MPa.m-0.5, which is a reasonable value, consistent with the results of other tests performed on standard test specimens as specified by ASTM. (P.A.)