Americium Valence Control Experiments in the Dissolved Solution of Irradiated Nuclear Fuel

Abstract

A method based on valence control and solvent extraction is presented for separating minor actinides (Am, Np) from nuclear fuel reprocessing solution. With this method, Am is adjusted from trivalence to hexavalence by adding 1.6M (NH₄)₂S₂O₈ and 0.01 M AgNO₃ to the solution of irradiated nuclear fuel. In the present study, the resulting valence of Am was determined by spectrophotometry. 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 solution, which results in lowering of the yield of Am(VI) to 90%±4% in a solution containing 15 g/l of Pu. Removal beforehand of Pu(IV) from the solution will permit Am(III) to be oxidized quantitatively. Neptunium also is oxidized to hexavalence under the same conditions that yield Am (VI). The resulting hexavalent actinides are both extractable with TBP (tri-n-butyl phosphate). This means that both the minor actinides americium and neptunium can be recovered from raffinate solution generated from the co-decontamination step in spent fuel reprocessing.

KEYWORDS:

• americium
• neptunium
• rare earths
• fuel reprocessing
• solvent extraction
• separation process
• valence control
• ammonium peroxodisulfate
• silver nitrate
• TBP
• recovery