Separation of Americium from Curium through Oxidation State Control with Record Efficiency

Abstract

Separation of americium (Am) from curium (Cm) could greatly facilitate the development of advanced nuclear fuel cycles, help with accurate nuclear forensic analysis, and allow for more efficient recovery and utilization of the two strategic elements. In this work, an Am/Cm separation strategy based on the stabilization of pentavalent Am in a biphasic solvent extraction system using bismuthate as the oxidant and N,N,N′,N′-tetraoctyl diglycolamide (TODGA) as the extractant was developed. The distinctive differences between Am(V) and Cm(III) in terms of both steric configuration and charge density afford record high Cm/Am separation factors (>10 4 ) through only one single contact in solvent extraction. This separation strategy possesses superior features including fast kinetics, long-time stability, no secondary solid radioactive waste generation, and applicability over a wide range of HNO 3 acidities, making it promising for Am/Cm separation and analysis in a variety of applications.

The Speciation of Americium Cations in Neat Water Implicated from DFT Studies

“…The multivalent nature of Am in aqueous solution provides an alternative choice to separate Am­(III) from Ln­(III) by manipulating the valence state of Am (oxidizing Am 3+ to its higher penta- and/or hexavalent oxidation states), during which lanthanides remain in their trivalent state although with some exceptions (e.g., Ce, Tb). − Benefitting from the large difference between their coordination chemistry and migration behaviors in the condensed phase and those of Ln 3+ , the Am­(V, VI)/Ln­(III, IV) separation are relatively easier to accomplish by using the established solvent extraction technology. A few studies have been reported in this respect; − however, the development of this protocol is impeded by the lack of sufficient knowledge on the speciation of Am in the condensed phase, which offers a compelling need for an extensive study on the coordination chemistry of Am in its various valence states and the conversion mechanisms between them.…”

A Simple yet Efficient Hydrophilic Phenanthroline-Based Ligand for Selective Am(III) Separation under High Acidity

“… , Additionally, the Eu­(III)/Am­(III) separation performances of Phen-2DIBA were further demonstrated in the stripping (back-extraction) experiment as described in the i -SANEX process for direct comparison with the procedures reported in the literature (Note 1 in the Supporting Information, data given in Tables S3 and S4) and results similar to those described above were observed. Lastly, the high selectivity of Phen-2DIBA toward Am­(III) was demonstrated by americium–curium separation, which was believed to be a more challenging process, as Am­(III) and Cm­(III) are adjacent actinides with nearly identical radii . Curium isotopes were short-lived, intensively radioactive, and strong neutron emitters which were proposed to be separated as early in the separation process as possible in order to develop a compact separation process. , The equilibrium separation factor of Phen-2DIBA toward Cm­(III) and Am­(III) was determined to be around 4.4 (Figure d).…”

Ion sieving in graphene oxide membrane enables efficient actinides/lanthanides separation

“…3e, f prove the efficient ion sieving of U and Np from the lanthanides by the GOM, the other two actinides Pu and Am largely penetrate together with the lanthanides into the RC, emphasizing the necessity of oxidation in the FC to separate Pu and Am from the lanthanides. To address this issue, sodium bismuthate (NaBiO 3 ), known as a highly oxidizing agent capable of oxidizing Am(III) to Am(VI) quantitatively in nitric acid solutions, was employed as the chemical oxidant in this work to oxidize the actinides 12 , 13 , 17 , 36 . Absorption spectra (Supplementary Fig.…”