A Molecular Dynamics Study Of Oxide Based Glasses For Potential Applications As Nuclear Waste Host

Abstract

The immobilization of high-level radioactive waste (HLW) is a critical challenge in the nuclear fuel cycle, necessitating the development of structurally durable and chemically stable waste forms. In this study, molecular dynamics (MD) simulations were employed to investigate the structural, dynamic, and radiation-tolerant properties of a complex borosilicate glass matrix composed of SiO₂, B₂O₃, Na₂O, BaO, ZrO₂, and UO₂. The objective was to assess its suitability as a potential host for the safe containment of actinide-rich nuclear waste. A melt-quench protocol was applied to generate an amorphous glass structure, followed by equilibrium and radiation-damage simulations using the LAMMPS simulation package. Structural analysis through radial distribution functions (RDFs), coordination number calculations, and Voronoi volume analysis revealed the presence of stable tetrahedra units, and ZrO₆ octahedra—suggesting a well-connected, radiation-tolerant glass network. Uranium ions were observed to be immobilized within the cage-like structure formed by Zr and O polyhedra, which effectively limited their mobility even under thermal and irradiation conditions. Displacement cascade simulations, initiated by imparting kinetic energy to uranium atoms (1–5 keV), demonstrated localized structural damage without long-range atomic diffusion, confirming the glass’s inherent resistance to radiation-induced destabilization. Mean squared displacement (MSD) analyses further confirmed negligible mobility of heavy ions like U, while lighter species such as Na⁺ reflecting the role of network modifiers in accommodating dynamic rearrangements. Post-radiation thermal annealing simulations suggested partial self-healing capabilities of the glass network, with RDF peaks and coordination distributions largely recovering to pre-damage states. Overall, the simulation results highlight the resonable structural integrity, uranium retention potential, and self-repair behaviour of the proposed borosilicate glass under radiation. These findings support its viability as a long-term nuclear waste host, contributing to the broader goal of safe and sustainable radioactive waste management.