The behaviour of caesium in nuclear fuels was investigated using density

functional theory. In a first step, the incorporation and solution energies of Cs in

pre-existing trap sites of UO2 (vacancies, interstitials, U–O di-vacancy and

Schottky trio defects) were calculated using the projector augmented wave derived

pseudopotentials as implemented in the Vienna ab initio simulation package.

Correlation effects were taken into account within the density functional theory +

U approach. The solubility of caesium was found to be very low, in agreement with

experimental data. The migration of Cs was found to be highly anisotropic, it was

controlled by uranium diffusion with an Arrhenius activation energy of 4.8eV in

hyperstoichiometric UO2+x, in good agreement with experimental values.

Ab Initio Study of Solution Energy and Diffusion of Caesium in Uranium Dioxide.

F.Gupta, A.Pasturel, G.Brillant: Journal of Nuclear Materials, 2009, 385[2], 368-71