Thermal removal of gallium from gallia-doped ceria

The potential for removing gallium from Ga-doped CeO2-x by thermal means wa s studied for the purpose of assessing gallium removal from PuO2-x. The lat ter is of interest to those considering the storage or use of weapon-grade Pu, for example as a mixed oxide fuel component. Experiments were done by v arying temperature, gas composition, exposure time, sample size, particle s ize, and gas flow rate. The kinetics of gallium removal were assessed throu gh measurements of weight change, scanning electron microscopy, and chemica l analyses. Results suggest that the gallium level can be reduced significa ntly by thermal treatments in Ar-6% H-2. Gallium species segregate to grain boundaries because of the low solubility of Ga2O3 in CeO2. The kinetics an d microstructural observations suggest that both gaseous and solid-state di ffusion of gallium species are important for the removal of gallium. (C) 20 00 Elsevier Science B.V. All rights reserved.