Localized ductility method for evaluating Zircaloy-2 cladding

The localized ductility method has been shown to be a useful laboratory method for evaluating the mechanical performance of fuel cladding under conditions that approximate that of pellet-clad interaction (PCI). Using the method on unirradiated annealed and cold-worked cladding, performance is determined in flowing gaseous iodine and cesium plus cadmium liquid metal. In the case of iodine, increasing temperature and decreasing strain rate enhance the embrittlement, as does a texture in which the basal pole is in the direction of the applied stress. Further, microcracking is not found to occur below a finite plastic strain. The behavior is consistent with a film rupture mechanism for chemical-assisted cracking. For cesium plus cadmium, cracking is found in Zircaloy-2 above a threshold level of stress as indicated by the performance of constant crosshead and predefected constant load tests. 17 refs