Investigations in Gallium Removal (ANRCP-1997-3)

Gallium present in weapons plutonium must be removed before it can be used for the production of mixed-oxide (MOX) nuclear reactor fuel. The main goal of the preliminary studies conducted at Texas A&M University was to assist in the development of a thermal process to remove gallium from a gallium oxide/plutonium oxide matrix. This effort is being conducted in close consultation with the Los Alamos National Laboratory (LANL) personnel involved in the development of this process for the US Department of Energy (DOE). Simple experiments were performed on gallium oxide, and cerium-oxide/gallium-oxide mixtures, heated to temperatures ranging from 700 900 C in a reducing environment, and a method for collecting the gallium vapors under these conditions was demonstrated. Background The scope of DOE’s integrated approach for weapons component conversions includes two options for plutonium disposition: (1) immobilization via vitrification/ceramification, or (2) use of the plutonium for fabrication of mixed uranium/plutonium oxide (MOX) fuel for commercial nuclear power reactors. However, weapons-derived plutonium contains approximately 1 weight percent gallium. Gallium at such concentrations presents various issues for MOX fuel fabrication and use. MOX fuel is a ceramic material, prepared by sintering oxides of uranium and plutonium, which are initially both in the form of fine powders. At high concentrations, gallium affects the sintering behavior of the ceramic. Since plutonium weapon components do not all have the same concentration of gallium, the sintering process parameters would have to be adjusted as the gallium concentration changed (undesirable in an industrial-scale operation) unless the gallium was reduced to an acceptable level prior to fabrication. In addition, there may be issues with using MOX fuel with excessive gallium concentration as a reactor