ThUO2

ThUO2, or thorium-uranium dioxide, is a mixed oxide ceramic in which thorium and uranium occupy the same cation sublattice within a dioxide lattice. The general composition is described by Th1−xUxO2, with 0 ≤ x ≤ 1, and the solid solution tends to adopt the fluorite-type cubic structure common to actinide dioxides. The material’s properties can be tuned by adjusting the thorium-to-uranium ratio, influencing lattice parameters, oxygen stoichiometry, and neutron economy.

Production typically involves forming a homogeneous mixture of ThO2 and UO2 powders, followed by high-temperature sintering under controlled atmosphere to achieve a single-phase solid solution. The resulting ceramic is a high-melting, chemically stable oxide whose thermal and irradiation behavior depends on composition, temperature, and burnup. Oxygen stoichiometry can deviate from ideal Th1−xUxO2 under non-stoichiometric processing, leading to oxygen-rich or oxygen-deficient variants that affect defect chemistry and transport properties.

In nuclear fuel research, Th1−xUxO2 fuels are studied as a potential thorium-based fuel cycle option. Thorium-232 can capture neutrons and breed U-233, a fissile isotope, enabling alternative pathways for sustaining fission reactions. Mixed Th/U oxides aim to combine the fertile advantages of thorium with the fissile content of uranium. Practical deployment faces challenges such as fabrication at scale, irradiation performance, fission-product management, and regulatory considerations, with ongoing investigations in test reactors and modeling efforts.

Related topics include thorium dioxide, uranium dioxide, mixed-oxide fuels, and thorium fuel cycles.