Separation of Am (V, VI) from Cm(III) and Pr(III) in Ammonia and Ammonium-Carbonate Media

Abstract

New approaches to the selective isolation of Am from the actinide–lanthanide fraction of high-level waste with preliminary oxidation of Am(III) to Am(V) and Am(VI) using ammonia and ammonia–carbonate media are proposed. When ammonium hydroxide is added to a 0.1 M HNO₃ solution containing Am(V), Cm(III), and Pr(III) (as a mimic of the behavior of lanthanides) to pH ~8, AmO₂⁺ shows increased stability and is retained in the solution to 80%, whereas Cm(III) and Pr(III) precipitate in the form of poorly soluble compounds. In ammonia–carbonate solutions at pH ~10, up to 96% of the initial amount of Am(VI) is retained in the solution, and Cm(III) and Pr(III) precipitate to 85%.