Mechanical Property Degradation of Unirradiated Zircaloy-4 Cladding After Creep Deformation

One of the limiting mechanisms of pressurized water reactor spent fuel cladding is creep owing to high temperature and rod internal pressure. Based on extensive studies, many countries have tentatively concluded that creep rupture is hard to occur under dry storage conditions and cannot severely degrade the integrity of the cladding if it meets the 400°C limitation owing to a self-limiting property. However, the changes in mechanical properties after creep deformation are not well understood due to the limited amount of relevant tests and analyses. In this regard, mechanical property degradation of unirradiated Zircaloy-4 cladding by creep deformation was investigated using a ring compression test and microscopic observation. In addition, the implication regarding spent fuel cladding integrity based on the test results is described.