Deformation and Fracture Properties of Stress Relieved Zircaloy-4 in Iodine, Cesium, Cadmium and a Mixture of Cesium Cadmium

The deformation behaviour, burst pressure and fracture appearance of stress relieved Zircaloy-4 cladding exposed to I, Cs, Cd and a mixture of Cs/Cd was investigated in controlled pressure ramps at 343 and 400 degree C. It was found that the deformation behaviour observed under iodine up to rupture is the same as that without iodine. Threshold stresses are increased by a homogeneous surface oxide layer as well as the homogeneous microstructure. Decreasing burst pressures to a threshold stress can be explained by crack formation after the threshold stress is transgressed and crack growth. Fractography showed that the fracture appearance due to the corrosion by a Cs/Cd-mixture was nearly undistinguishable from that due to iodine