Modelling Fission Gas Bubble Distribution in UO2

The Cluster Dynamics method is assessed for the investigation of fission gas behaviour in a krypton-implanted and annealed UO2 sample. The simulation results are then compared to Thermal Desorption Spectroscopy (TDS) data. A release mechanism is proposed: the initial burst is related to krypton migration via an interstitial mechanism, while the second stage of the release process can be accounted for by the diffusion of krypton in a substitutional position. This latter mechanism is compatible with a diffusion coefficient of 4.10(-21) m(2)/s.