Radionuclide Sequestration in Functionalized Montmorillonite Clay from Molecular Dynamics Simulations

Safe and reliable storage of radioactive waste (vitrified high-level waste (HLW) and spent nuclear fuel (SNF)) is a necessity for effective nuclear power infrastructure. Proper disposal requires buffer materials which can sequester radionuclides such as iodine and technetium for durations of up to 10⁶ years. In this work, the performance of functionalized montmorillonite as a buffer material is evaluated via molecular dynamics (MD) simulations. Functionalizing agents such as alkylammonium, thiol groups, and metallic species react via interlayer exchange to capture the anionic radionuclides which would otherwise be electrostatically repulsed by montmorillonite’s net negative charge. The simulations utilize a combination of ClayFF, SPC/e, and OPLSAA potentials to parameterize interactions between the clay sheet, water, and organic functionalizing agents respectively. Differences in performance between a neutral charge pyrophyllite clay, unfunctionalized montmorillonite, and montmorillonite with various functionalizing agents are evaluated to inform an optimal choice for future buffer material applications.<br/> <br/>This work was supported by the US Department of Energy Office of Nuclear Energy NEUP Project Number 20-19198.