Molecular dynamic simulation of fission fragment induced thermal spikes in UO2: Sputtering and bubble re-solution

Sputtering and the re-solution of Xe fission gas bubbles in UO2 due to electronic energy deposition of fission fragments is investigated using molecular dynamic (MD) simulations. First, a two-temperature model coupling the electronic (e-) and phonon (p-) systems is employed to determine the temperature profile along the tracks of fission fragments. The e–p coupling constant within the model is determined by comparing the sputtering yields deduced from the MD simulations with those obtained experimentally. Next, fission fragments tracks are simulated in UO2 containing Xenon bubbles. At high (dE/dx)e bubbles are partially dissolved, however, for ions with electronic stopping powers lower than 34 keV/nm, no bubble re-solution is observed. Thus, bubble re-solution due to the electronic stopping of fission fragments in UO2 is expected to be insignificant compared to homogeneous re-solution.