Comparison of J-parameters of cold worked and stress relieved Zr–2.5Nb pressure tube alloy determined using load normalization and direct current potential drop technique

•Fracture toughness of Zr–2.5Nb alloy PT between 30 and 300 °C was determined.•The J0.15 and JQ determined using LNT was >40% higher than that obtained using DCPD.•The Jmax, J1.5 determined using LNT was comparable to that obtained using DCPD.•The dJ/da values determined using LNT were ∼25%< that determined using DCPD.•The CCL for catastrophic failure of PT is not sensitive to analysis method.

The fracture toughness of Zr–2.5Nb pressure tube alloy used in Indian Pressurized Heavy Water Reactor was determined in the temperature range of 30–300 °C using load normalization technique (LNT) and a comparison between the crack initiation and the crack propagation toughness parameters is presented with the values obtained using direct current potential drop (DCPD) technique. The dependence of error in J-parameters determined using LNT to that obtained using DCPD on temperature and final crack extensions was also investigated. Below 200 °C, the error exhibited weak dependence on final crack extensions. Above 200 °C the error in initiation toughness increased significantly while the error in propagation toughness was practically unaffected.