Precise determination of plutonium in nuclear fuel process samples

A REDOX-based analytical method was developed for determining the plutonium concentration. In this method, plutonium was oxidized to the +6-oxidation state using of ceric ammonium nitrate solution. The interference from ceric(IV) nitrate was suppressed by reducing its oxidation state from +4 to +3 with sodium nitrite. Hexavalent plutonium in this sample was then reduced to be tetravalent by adding a known volume of excess standard ferrous ammonium sulphate. The dichromate equivalence required for unreacted ferrous ammonium sulphate was determined to obtain the concentration of plutonium. Interference studies from chemicals envisaged to be present in the PUREX process stream, such as dissolved tri-n-butyl phosphate, uranium, and various reagents employed during analysis, were performed for the determination of plutonium concentration. The relative standard deviation was found and it is within ±1.0% for an aliquot containing plutonium in a range of 0.7-2.5 mg. (author)