A simulation of the helium diffusion in uranium dioxide crystals: a comparison of the interaction potentials

Abstract

The article studies interaction of radiogenic gases, such as helium with oxide nuclear fuel. The problem of molecular-dynamic modeling of the processes of helium accumulation and diffusion in uranium dioxide crystals is considered. The simulations are carried out taking into account the high energy of the particles (up to 100 keV), characteristic of cascade collisions. The potentials of interaction of helium atoms with oxygen and uranium ions are proposed, applicable in the range from the energy of thermal motion to hundreds of keV. The well-known potentials of helium interaction in UO2 crystal (R.W. Grimes [1], E. Yakub [2]) are compared with these proposed in this paper. Using molecular dynamics, the coefficients of helium interstitial diffusion are calculated for the temperatures from 1500 K to the melting point, the values from 110–4 to 110–7 cm2/s are obtained. The corresponding activation energies varied from 2 to 2.7 eV, depending on the interaction potentials. The results are compared with the experimental data and molecular dynamics calculationsof other authors. The calculated values of the diffusion coefficient are shown to be close to the experimental data on helium interstitial diffusion for the fluorite crystal considered as a structural analogue of the oxide fuel.