DELAYED HYDRIDE CRACKING IN ZIRCALOY FUEL CLADDING - AN IAEA COORDINATED RESEARCH PROGRAMME

The rate of delayed hydride cracking (DHC), V, has been measured in cold-worked and stress-relieved Zircaloy-4 fuel cladding using the Pin-Loading Tension technique. At 250 degrees C the mean value of V from 69 specimens was 3.3(+/- 0.8)x10(-8) m/s while the temperature dependence up to 275 degrees C was described by Aexp(-Q/RT), where Q is 48.3 kJ/mol. No cracking or cracking at very low rates was observed at higher temperatures. The fracture surface consisted of flat fracture with no striations. The results are compared with previous results on fuel cladding and pressure tubes.