Molecular dynamics simulations were carried out to study the influence of grain

boundaries in stoichiometric UO2 on uranium and oxygen self-diffusion at 300 to

2100K. The study was carried out on two symmetrical tilt grain boundaries, Σ5 and

Σ41, which have respectively two different atomic structures. Firstly, the study of

the temperature effect on the grain boundary core structure was presented. With the

raise of temperature, the grain boundary core grew with an increase of disorder. Secondly, self-diffusion near both grain boundaries was studied. It was found that

grain boundaries accelerate the uranium and oxygen self-diffusion rates over

several nanometres from the grain boundary interface. Uranium and oxygen selfdiffusion

were anisotropic, with a high acceleration along the grain boundary

interface. Using the self-Van Hove correlation functions, hopping mechanisms

were identified for Σ41 in all directions while for Σ5 hopping mechanism takes

place along the grain boundary interface and random diffusion appeared in the

perpendicular direction of the grain boundary plane.

Self-Diffusion Near Symmetrical Tilt Grain Boundaries in UO2 Matrix: a

Molecular Dynamics Simulation Study. E.Vincent-Aublant, J.M.Delaye, L.Van

Brutzel: Journal of Nuclear Materials, 2009, 392[1], 114-20