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

Abstract

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.