Cumulative damage fatigue tests on nuclear reactor Zircaloy-2 fuel tubes at room temperature and 300°C

Cumulative damage fatigue tests were conducted on the Zircaloy-2 fuel tubes at room temperature and 300°C on the modified Moore type, four-point-loaded, deflection-controlled, rotating bending fatigue testing machine. The cumulative cycle ratio at fracture for the Zircaloy-2 fuel tubes was found to depend on the sequence of loading, stress history, number of cycles of application of the pre-stress and the test temperature. A Hi-Lo type fatigue loading was found to be very much damaging at room temperature and this feature was not observed in the tests at 300°C. Results indicate significant differences in damage interaction and damage propagation under cumulative damage tests at room temperature and at 300°C. Block-loading fatigue tests are suggested as the best method to determine the life-time of Zircaloy-2 fuel tubes under random fatigue loading during their service in the reactor.