A Synergistic Stabilization Strategy for Room-Temperature Internal Gelation Process: From Zirconia Surrogates to Uranium Fuel Microspheres

The internal gelation process is essential for producing spherical nuclear fuel micro-spheres. However, its application is constrained by the poor room-temperature stability of conventional broths and by the inherent trade-off between stability and strength. A novel five-component broth system (ZrO(NO₃)₂-HMTA-urea-acetylacetone (ACAC)-glucose) was developed. The synergistic effects of ACAC and glucose on sol stability and gelation ki-netics were systematically investigated. An optimal ACAC/glucose molar ratio of 1:1 and an ACAC/ZrO2+ ratio of 1.5 were identified, yielding a broth stable for over 5 h at 25°C. The resulting yttrium stabilized zirconia (YSZ) microspheres exhibited excellent sphericity (1.04±0.01), density (5.84 g/cm³), and crushing strength (8.0 kg/sphere). This stabilization strategy was successfully extended to a uranium system, enhancing its room-temperature stability from minutes to 6 h. The work demonstrates that the synergistic ACAC-glucose system effectively decouples the stability-strength dilemma. Its successful application to a uranium broth confirms the broader utility of the dicarbonyl complexation strategy, providing an energy-efficient route for producing high-quality nuclear fuel microspheres.