Redistribution of Hydrogen in Fuel Cladding and Its Influence on Mechanical Properties of Cladding under Dry Storage Conditions

Hydrogen redistribution process in Zircaloy cladding of spent fuels was evaluated under the thermal condition of dry storage． Charpy impact test was carried out at temperatures from room temperature to 523 K on two kinds of Zircaloy specimens including 400 wt-ppm of hydrogen：One is the specimen in which hydrogen （hydride）is uniformly distributed and the other in which hydrogen is nonuniformly distributed． These tests show that the impact strength of the specimen with non-uniform hydrogen distribution is larger than that of the specimen with uniform distribution． On the basis of these results， the possibility that the impact strength of the cladding including large amount of hydrogen is degraded during the dry storage was suggested；e．g． in the case of the cladding including 400 ppm hydrogen， the uniform distribution of hydrogen is realized when the cladding is heated up to 773 K