SGMP-an advanced method for fabrication of UO₂ and mox fuel pellets

Abstract

The External Gelation of Uranium (EGU) process, though originally developed for preparation of fuel particles for High-Temperature Reactors (HTR), was also found to be attractive for Sol-Gel Microsphere Pelletization (SGMP) of UO₂ and mixed oxide (MOX) fuel. No major changes of the process were necessary. However, for producing "porous microsphere" carbon black was added to the broth and later burnt out from the gel micropheres. Both "porous" and "non-porous" microspheres have been easily pelletized and sintered to high densities (≥ 95% TD) at relatively low temperatures (≤ 1500 ° C) in CO₂ atmosphere. The "porous" microspheres led to sintered pellets having closed pores in the diameter range of 2-5 µm. Such pellets are good for retention of fission gases and are hence recommended for water-cooled reactor fuel pins. The pellets prepared from "non-porous" microspheres had "open pores" and are suitable for LMFBR fuel pins. UO₂-5% CeO₂ and UO₂-30% CeO₂ were chosen to simulate MOX fuels for thermal and fast reactors, respectively.