FLUKA study of the actinides induced irradiation damage in Zircaloy-4 cladding during interim dry storage

Among the factors influencing degradation of spent nuclear fuel cladding in interim dry storage, irradiation history and average burnup at discharge must be considered. In fact, due to pellet-cladding contact particularly affecting high fuels, inner surface becomes increasingly exposed damage caused by alpha decaying actinides present rim pellet. Moreover, low temperature conditions characteristic thermal recombination produced defects is not expected occur. Here, we investigate accumulated inside an irradiated Zircaloy-4 32, 55 100 years after end from reactor core. The considered cladded UO 2 pellet belongs a Pressurised Water Reactor (PWR) rod consisting five segments having 50.4 GWd t HM − 1 . calculations performed with FLUKA 2021.2.0 Monte Carlo code show that volume mostly affected corresponds ZrO layer formed between cladding. which are responsible for mainly 242 Cm , 244 241 Pu 238 recoiling daughter nuclei during decays produce only within first µm oxide