Fabrication of UO2–Mo composite fuel pellets with enhanced thermal conductivity by using wet mixing

Jan. 26, 2026, 2:52 p.m. - by Fihan Alharbi , Hywel Ragnauth , Timothy Abram , Joel Turner

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Uranium dioxide (UO₂) is widely used as fuel in light water reactors (LWRs owing to its proven in-reactor performance, irradiation stability, and manufacturability. Nevertheless, its inherently low thermal conductivity generates steep temperature gradients within fuel pellets during operation, which can induce thermal stresses, dimensional changes, and cracking. In this study, the incorporation of a high–thermal-conductivity molybdenum phase in the form of a nanopowder is investigated as a strategy to enhance pellet heat transport. Nano-sized Mo powder was combined with pre-sintered UO₂ granules, dispersed in ethanol during mixing, followed by solvent removal and consolidation via spark plasma sintering (SPS) at 1473 K with a 5-minute dwell. Composite pellets containing 10 wt.% Mo were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD), while thermal conductivity was determined using the laser flash technique. The as-fabricated composites exhibited substantial improvements in thermal conductivity, with increases of up to 75% at 1073 K relative to monolithic UO₂ pellets. These findings demonstrate that the combined use of nano-Mo additions and pre-sintered UO₂ granules is an effective approach for improving the thermal performance of UO₂-based nuclear fuel materials.

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