Modeling high-energy radiation damage in nuclear and fusion applications

We discuss molecular dynamics (MD) simulations of high-energy radiation damage in materials relevant for encapsulation of nuclear waste and materials to be used in fusion reactors, including several important oxides and iron. We study various stages of evolution and relaxation of 100-200 keV collision cascades, and identify reversible elastic and irreversible inelastic structural changes. The elastic expansion of the lattice around the cascade is explained in terms of anharmonicity of interatomic interactions. The remaining irreversible structural change is related to resistance to amorphization by radiation damage. This resistance is quantified by the number of remaining defect atoms in the damaged structure. We discuss how MD simulations can predict experimental resistance to amorphization, including the important case of highly resistant materials. Finally, we discuss our current work to simulate radiation damage of MeV energies and system sizes of the order of billion atoms using massive parallel computing facilities.