(497d) Atomistic Insights into Transient Covalent Bonding in Molten Uranium Chloride and Implications for Pyrochemical Separations in Advanced Nuclear Reactors
2025 AIChE Annual Meeting
(497d) Atomistic Insights into Transient Covalent Bonding in Molten Uranium Chloride and Implications for Pyrochemical Separations in Advanced Nuclear Reactors
Molten salt reactors (MSRs) hold significant promise for revolutionizing nuclear energy by enhancing reactor safety, efficiency, and sustainability. Central to realizing their potential is the mastery of chemical processes within high-temperature molten salts, particularly regarding uranium speciation and its separation from fission products. Our recent investigation into molten uranium trichloride (UCl₃) using a synergistic experimental and computational approach uncovered unprecedented chemical behavior: the formation of short, transient covalent U–Cl bonds resulting from the enhanced participation of uranium's 5f valence orbitals. This transient covalency creates a heterogeneous bonding environment characterized by distinct inner- and outer-coordination shells, influencing the chemical reactivity and separability of uranium from lanthanide fission products during pyroprocessing.
In this presentation, I will discuss how advanced characterization methods, including high-temperature neutron scattering, X-ray absorption spectroscopy, and first-principles atomistic molecular dynamics simulations enabled these findings. Such atomic-level understanding provides critical insights into the fundamental chemical behaviors of molten fuel occurring under extreme reactor-relevant conditions. These discoveries directly inform the rational design and optimization of pyrochemical separation methods, advanced fuel cycle processes, and corrosion-resistant structural materials, laying the groundwork for safer, more efficient, and economically viable nuclear energy systems.
