Atomic scale simulations of noble gases behaviour in uranium dioxide

Nuclear fuel performance is highly affected by the behaviour of fission gases, particularly at elevated burnups, where large amounts of gas can potentially be released. The importance of fission gas release was the motivation for large efforts, both experimentally and theoretically, to increase our understanding of the different steps of the process, and to continuously improve models. Extensions to higher burnups, together with the growing interest in novel types of fuels, make that one is still looking for a better modelling, based on a physical understanding of all stages of the release mechanism. In this work computer simulation techniques based on empirical potentials have been used, focusing in a first stage on pure UO2. Then, in a second stage, the study has been extended to the diffusive behaviour of helium and xenon. Xenon behaviour has been investigated with the additional intention to model the behaviour of small intragranular bubbles, particularly their interaction with thermal spikes. For that purpose, a simplified description of these events has been proposed, which opens perspectives for further work.