Sol-gel microsphere pelletization: A powder-free advanced process for fabrication of ceramic nuclear fuel pellets

Hydrated gel-microspheres of U, Pu, Th oxide or oxide plus carbon mixture of diameter 400–800µ were prepared by ammonia gelation processes. They were dried and subjected to suitable treatment for obtaining free-flowing oxide, carbide or nitride micro-spheres of diameter 200–400µ suitable for direct pelletization and sintering. The oxide, carbide and nitride pellets were, in general, sintered at high temperature in Ar+8% H₂. However, for UO₂ and (U, Pu)O₂ pellets low temperature (1200 °C), short duration (1 h) oxidative (CO₂ or N₂+air) sintering (LTS) was also successful, thereby reducing electrical energy and gas consumption during sintering. Thus, the combined SGMP-LTS process simultaneously minimized “radiotoxic dust hazard” and fuel fabrication cost in case of UO₂ and (U, Pu) O₂ pellets.