It was found that the migration activation enthalpies, as predicted using atomistic simulation methods, depended sensitively upon the fuel stoichiometry. The mechanisms in stoichiometric and non-stoichiometric fuel required the occurrence of U self-diffusion, apart from the case of I. The latter involved an anion vacancy mechanism. Post-irradiation I data compared well with the predicted activation enthalpy. In-pile I-release data indicated a reduced activation enthalpy for I migration. The diffusion model which was presented allowed for the situation in which U diffusion was greatly affected by irradiation.

The Diffusion of Iodine and Caesium in the UO2 Lattice. G.Busker, R.W.Grimes, M.R.Bradford: Journal of Nuclear Materials, 2000, 279[1], 46-50