Effects of hydride rim on the ductility of Zircaloy-4 cladding

High burn-up nuclear fuel cladding has a hydride rim owing to hydrogen diffusion under a temperature gradient. To simulate the high burn-up cladding, the hydride rim was formed in un-irradiated Zircaloy-4 cladding and ductility evaluation was conducted using ring compression test (RCT). The RCTs were conducted from room temperature to 300 °C for determining the ductile to brittle transition temperature (DBTT) of hydrided Zircaloy-4 cladding. Hydride rimmed specimens have lower ductility and DBTT than uniform hydrided specimens. The increased ductility at high temperatures is likely due to the increased ductility of the Zr matrix because the fractography at hydride rim still shows brittle fracture at those temperatures. The ductility of hydride rimmed specimens with radial hydrides are compared with those of irradiated Zr alloy claddings, and thus, it is concluded that hydride rimmed specimen can simulate the high burn-up Zr alloy cladding to some extent.