Thermochemical Reduction of Uranium Hexafluoride for the Direct Fabrication of Uranium Dioxide Ceramic Fuels

Thermochemical reduction of uranium halides is being investigated at the Oak Ridge National Laboratory as a means of fabricating high-density refractory uranium compounds for fuel element application. A one-step conversion of uranium hexafluoride to uranium dioxide has been effected by combining the uranium hexafluoride with hydrogen and oxygen at elevated temperatures and reduced pressures. The product may be deposited as a submicron powder, dendritic crystallites, or a solid approaching theoretical density depending upon reaction pressure and gas-mixing techniques. The stoichiometry of the solid deposit may be controlled by adjusting the ratios of the gaseous reactants. It is anticipated that the process might be optimized for fuels having high enrichments or for reprocessing contaminated fuels, thus giving more-efficient controlled conversion to a desired form. The results also indicate that other refractory oxides may be produced as free-standing bodies through the use of similar techniques.