Characterisation of Cr2O3 Doped Fuel

In this paper, the fuel that will be irradiated in the IFA-716 experiment of the OECD Halden Reactor Project programme was further characterised by EPMA and XRD. By EPMA, the amount of chromium dissolved in the UO2 matrix was estimated and a value of 964 ppm was found. This value is consitent with literature values. As expected, part of the chromia has been evaporated at the fuel pellet periphery during sintering. The presence of Cr2O3 precipitates was observed for all the Cr2O3 doped fuel pellets, even for the fuel pellets which contain a chromia amount below the solubility limit. The results obtained by EPMA were confirmed by XRD analysis, which showed that most of the chromia is present in the UO2 matrix. Indeed, the lattice parameter decreased linearly with increasing amount of chromia dissolved in the fuel matrix. The scoping study performed using empirical interatomic potentials leaded to an improved understanding of the behaviour of chromium in the UO2 lattice. The substitutional behaviour of chromium was predicted both by computing the defect energies for different types of defect clusters and by calculating the lattice deformation in the presence of these defects.