Qualification of a Physical Model of Cladding Creep During Dry Storage of Spent Nuclear Fuel

Sammanfattning: In dry interim storage of spent nuclear fuel, thermal creep is one of the major threats to the fuel cladding integrity due to the constant decay heat generation from the fission products and minor actinides in the fuel, and the increase in fuel rod internal pressure which is present after burnup. Plenty of research has been done on either empty cladding tubes irradiated in a research reactor, or on spent fuel that is defueled prior to the examination. This type of research excludes the effects of the pellet-cladding bonding that may be present after burnup, where the bonding might have significant effects on the thermal creep behavior. Therefore, this work aims to construct and validate an experimental model that is designed to perform thermal creep tests on as-received spent nuclear fuel, where the pellet-cladding bonding is still intact, in order to gain knowledge in the causal relation that the pellet-cladding bonding has on the thermal creep phenomenon during dry storage. The experimental model is validated by a number of qualification tests, as well as a series of creep tests on unirradiated Zircaloy-4 tubes. The results are compared to the literature which shows the reproducibility of the model, which further supports its validity.