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.