Americium valence control experiments in the dissolved solution of irradiated nuclear fuel

A method based on valence control and solvent extraction is presented for s eparating minor actinides (Am, Np) from nuclear fuel reprocessing solution. With this method, Am is adjusted from trivalence to hexavalence by adding 1.6 M (NH4)(2)S2O8 and 0.01 M AgNO3 to the solution of irradiated nuclear f uel. In the present study, the resulting valence of Am was determined by sp ectrophotometry. The oxidizing reaction of Am(III) to Am(VI) is exposed to competition by the oxidation to Pu(VI) of the Pu(IV) co-present in the solu tion, which results in lowering of the yield of Am(VI) to 90%+/-4% in a sol ution containing 15 g/l of Pu. Removal beforehand of Pu(IV) from the soluti on will permit Am(III) to be oxidized quantitatively. Neptunium also is oxi dized to hexavalence under the same conditions that yield Am(VI). The resul ting hexavalent actinides are both extractable with TBP (tri-n-butyl phosph ate). This means that both the minor actinides americium and neptunium can he recovered from raffinate solution generated from the co-decontamination step in spent fuel reprocessing.