Fracture resistance of zirconium alloys

The fracture resistance of Zr-2.5Nb alloy is studied. It is shown that under the action of irradiation (up to 0.02-0.03 wt.%) the critical fracture temperature shifts markedly to the region of positive values and can reach 300-350 deg C. The samples of the above alloy have been used to study the critical magnitude of crack opening at the crack moving in various directions. The smallest magnitudes are shown to correspond to the cracks that develop in a radial direction. A relation between the critical sizes of the defects in zirconium-alloy tubes and the breaking defects have been found. Conditions are established under which the surface defect in a tube, in the process of its development into a through crack, results in a complete failure of a tube