The effect of temperature upon the rate of release of tritium from neutron-irradiated polycrystalline and single-crystal UO2 was studied. The diffusion coefficients for tritium at 500 to 1000C were found to be several orders of magnitude lower than those reported for molecular hydrogen in UO2 single crystals. The Arrhenius plots for both polycrystalline and monocrystalline samples were described by:

D(cm2/s) = 0.12 exp[-43.6(kcal/mol)/RT]

D.Scargill: Journal of Nuclear Materials, 1978, 74[1], 62-7