The effect of fission-energy Xe ion irradiation on dissolution of UO$_2$ thin films

Abstract

The aim of this work was to study the effect of fission fragment damage on the dissolution of UO$2$ thin films in water. For this purpose, thin films of UO$2$ on LSAT (Al${10}$La$3$O${51}$Sr${14}$Ta$_7$) substrates were produced and irradiated by 92 MeV $^{129}$Xe$^{23+}$ ions to a fluence of 4.8 × 10$^{15}$ ions/cm$^2$ 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 O$_2$ ppm in N$_2$ ) to study the effect of the induced irradiation damage and mixing on the dissolution of the UO$_2$ 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 UO$_2$ films with the substrate elements, which resulted in stabilisation of the UO$_2$ matrix and increased its aqueous durability. Secondary phases were also observed on the surface of the UO$_2$ films after the dissolution experiment.