Insights into Radiation Tolerance of Ceramics from Large Scale Molecular Dynamics Simulations

Abstract

Radiation tolerant ceramics are needed to advance the utilization of nuclear energy to meet rising global energy demand. They have potential to meet the demanding radiation environments in applications as nuclear fuel and waste forms. Their discovery and development are hampered by a lack of fundamental understanding of the physics underlying radiation tolerance of ceramics. Several theories have been advanced in the literature based on structure, radius ratio of cations and ionicity or covalency of bonds. Most of these theories focus on defect production and accumulation processes only, but neglect in-cascade and thermal annihilation of defects. We have performed large scale molecular dynamics simulations of 30 keV U and Zr recoils in zircon (ZrSiO₄), zirconia (ZrO₂) and yttria-stabilized zirconia (YSZ) to understand the atomic-level mechanisms that contribute to radiation tolerance, particularly fast annihilation processes. Zircon is amorphized by irradiation, while zirconia and YSZ do not undergo radiation-induced amorphization. Our results reveal that dynamic defect annihilation is very effective at controlling defect accumulation in radiation tolerant materials. Based on our results, we will discuss a strategy for improving the radiation tolerance of ceramics.