Abstract:
Zircaloy-4 is a zirconium alloy that will be used for construction of many of the core components in the replacement
research reactor at Lucas Heights. The fracture toughness of the alloy and its radiation-induced reduction over the 40
year planned life of the reactor is an important mechanical property for this application. This study aims to simulate the
radiation-induced reduction in fracture toughness by hydriding Zircaloy-4. A range of fracture toughnesses is required
to calibrate the sub-size Charpy and small punch (SP) surveillance specimens that will be irradiated over the life of the
reactor against standard JIC fracture toughness specimens. Pieces of Zircaloy-4 plate were hydrided in a vessel at a
temperature of 520°C, at different pressures for either 10 or 22 hours. Final hydrogen concentrations between 25 wt%
ppm and 380 wt% ppm hydrogen were obtained under gaseous atmosphere. The fracture toughness of the hydrided
Zircaloy-4 was assessed using sub-size 2.5 mm-thick Charpy, three-point bend JIC and SP tests. The results were
correlated to determine the relationship between the J-integral fracture toughness, Charpy impact energy and equivalent
fracture strain (Eqf) from the SP tests. It was found that as hydrogen concentration and hydride formation increased, the
fracture toughness of the alloy generally decreased. The results show there to be a useful relationship between fracture
toughness and Eqf measured for the SP tests.
