Effect of metallurgical variables and temperature on the fracture toughness of zirconium alloy pressure tubes

This paper summarizes the results from over 300 fracture toughness tests on compact specimens taken from zirconium alloy pressure tubing, primarily Zircaloy-2 and cold-worked Zr-2.5Nb. Test conditions include temperatures from 20 to 3000C, varying hydrogen concentrations and hydride orientations, irradiation at several temperatures, and irradiation times up to ten years. A thorough analysis of the results shows that strength and hydride orientation are the principal factors affecting toughness. An extremely steep ductile-brittle transition is observed in alloys containing hydride platelets in the radial (through-wall) orientation