Title: LABORATORY STUDIES ON THE USE OF URANIUM(IV) AS A PLUTONIUM REDUCTANT IN A PUREX PROCESS

This report describes laboratory-scale studies made to evaluate the feasibility of using uranium(IV)-hydrazine instead of ferrous sulfamate-sulfamic acid as the partitioning agent in the Hanford Atomic Products Operation Purex separations plant. Iron(II), in combination with sulfamic acid as a holding reductant, has been used very successfully for many years as a plutonium reductant in solvent extraction separation processes for irradiated nuclear fuels. However, the iron remains in the radioactive wastes produced in the separation processes. Its presence in these wastes accelerates corrosion of waste concentration equipment, complicates treatment of the waste for by-product recovery and adds to the total quantitymore » of contaminated salts which must be stored. Much effort has gone into searches for plutonium reductans which would not have the disadvantages associated with iron(II). Uranium(IV) has been proposed since, having acted as reductant, it is extracted along with uranium from the irradiated fuels and does in solvent extraction separations processes have involved mixer-settler contactors. The HAPO Purex plant has pulsed-column contactors. This difference, plus certain problems due to the particular flowsheet conditions used, required that additional laboratory studies be made to determine the feasibility of using uranium(IV) in the HAPO Purex plant.« less

Practical procedures were demonstrated for partitioning plutonium from uranium in the Purex process with hydrazine-stabilized uranium(IV) nitrate as the reducing reagent for plutonium. Typical partitioning results were 0.04--0.2% loss of plutonium to the uranium product and less than 1 wt% uranium in the plutonium product. With uranium(IV) nitrate as a replacement for ferrous sulfamate, most solids in wastes from the Parex process can be eliminated. No undue hazard is expected from the use of hydrazine as the stabilizing agent. (auth)