The solution and diffusion of ruthenium in UO2±x

Atomic scale computer simulation is used to develop models that describe the behaviour of ruthenium in the uranium dioxide lattice. Results are consistent with observed metal particle formation in UO2−x and UO2. Conversely it is predicted that ruthenium can be soluble in UO2+x although in irradiated fuel the extent of ruthenium solution will depend on the total concentration of fission products compared to the oxygen interstitial ion concentration. Second phase oxide particles such as BaRuO3 and RuO2 are not predicted to be stable. At all stoichiometries activation energies for migration are high.