The effect of fission-energy Xe ion irradiation on dissolution of UO2 thin films

The aim of this work was to study the effect of fission fragment damage on the dissolution of UO2 thin films in water. For this purpose, thin films of UO2 on LSAT (Al10La3O51Sr14Ta7) substrates were produced and irradiated by 92 MeV 129Xe23+ ions to a fluence of 4.8 × 1015 ions/cm2 to simulate the fission damage and induce chemical mixing that occur within nuclear fuels. The dissolution experiment was conducted under a nitrogen atmosphere (200-900 O2 ppm in N2) to study the effect of the induced irradiation damage and mixing on the dissolution of the UO2 matrix. The irradiated samples showed a decrease in the amount of dissolved uranium, as compared to the corresponding unirradiated samples. This was ascribed to the irradiation-induced chemical mixing of the UO2 films with the substrate elements, which resulted in stabilisation of the UO2 matrix and increased its aqueous durability. Secondary phases were also observed on the surface of the UO2 films after the dissolution experiment.