Atomic Scale Investigation of Lanthanide Substitution in Urania (UO 2 )

Uranium-based fuels are widely used for commercial nuclear energy generation as well as current and proposed nuclear reactors for space applications. The fission of UO2 generates a variety of fission products which affect the thermo-physical properties of the nuclear fuel. In this study we have characterized the effect of Lanthanides on the structural properties of urania fuel. Using atomic level simulations we have analyzed the effect of different concentrations of Lanthanides on UO2 matrix. Our results show that Lanthanides with smaller ionic radii compared to U 4+ ion reduces the overall lattice parameter, while Lanthanides with larger ionic radii increases the lattice parameter of the urania matrix. This observed variation in lattice parameter is explained by the elastic and/or electrostatic effects generated due to the particular ion substitution. A linear relationship between concentration and change in lattice parameter is predicted for all the Lanthanides.