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 mixt ure of diameter 400-800 mu were prepared by ammonia gelation processes . They were dried and subjected to suitable treatment for obtaining fr ee-flowing oxide, carbide or nitride microspheres of diameter 200-400 mu suitable for direct pelletization and sintering. The oxide, carbide and nitride pellets were, in general, sintered at high temperature in Ar + 8% H-2. However, for UO2 and (U, Pu)O2 pellets low temperature ( 1200-degrees-C), short duraton (1 h) oxidative (CO2 or N2 + air) sinte ring (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 fabricat ion cost in case of UO2 and (U, Pu)O2 pellets.