Some studies on the oxidation of plutonium III by vanadium V

The use of vanadate in the conditioning of plutonium to plutonium IV in aqueous nitric acid solution prior to solvent extraction has been examined by potentiometric and extraction techniques. Potentiometric studies show that the oxidation of plutonium III by vanadium V is rapid, quantitative reaction when the plutonium IV product is complexed. Observed potentials are close to the protentials predicted from the standard electrode potentials. Calculations predict that, under the conditions used for conditioning trace plutonium levels prior to extraction, vanadium V will result in an equilibrium mixture of plutonium III and IV, which will swing to complete oxidation as the plutonium IV is extracted. Extraction experiments confirm that conversion to plutonium IV is complete by the end of the extraction period. The extraction studies also show that no plutonium VI is produced by vanadate oxidation. The validity of the technique used is demonstrated by the use of dichromate in place of vanadate. These studies confirm that the sequential use of ferrous and vanadate at room temperature is a valid, effective and rapid technique for conversion of microgramme quantities of plutonium IV prior to solvent extraction. (author)