CHON AmSel: A New Extraction System for Selective Americium Partitioning Based on an Unsymmetrical Diglycolamide and a Sulfur-Free Complexant

One of the challenges of implementing a sustainable Partitioning and Transmutation (P&T) strategy in the nuclear fuel cycle is the development of a solvent extraction system for the selective separation of Am. One of the latest developments is the Americium Selective (AmSel) extraction system, a two-step process based on a lipophilic diglycolamide and a hydrophilic, sulfonated bistriazinyl bipyridine. However, this process has as a drawback the presence of sulfur in the hydrophilic complexant, making it unsuitable within a CHON strategy. This study presents a sulfur-free “CHON” variant of the AmSel process, replacing TODGA with N,N-dipentyl-N’,N’-didodecyldiglycolamide (PnDdDGA), and replacing SO3-Ph-BTBP with either 3,3′-([2,2′-bipyridine]-6,6′-diylbis(1H-1,2,3-triazole-4,1-diyl))bis(propan-1-ol) (PrOH-BPTD) or 3,3′-((1,10-Phenanthroline-2,9-diyl)bis(1H-1,2,3-triazole-4,1-diyl))bis(propane-1,2-diol) (BTrzPhen-tetraol). The latter two molecules are a hydrophilic bipyridine and phenanthroline, respectively. Both the organic and aqueous phases were optimized, and extraction tests were performed with a simulated highly active raffinate solution. Efficient separation of Am(III) from Cm(III) was feasible with both ligands, with SFCm/Am values of around 2.2. although the limited solubility of PrOH-BPTD requires lowering of the DGA concentration for stripping to occur. Demonstration on a simulated PUREX HAR lowered SFCm/Am values to around 1.9, and showed separating Am(III) from most fission products was possible. Separating Am(III) from La(III), Ce(III), and Pr(III) was not feasible in the stripping step, and necessitated an intermediary scrubbing step for the (light) lanthanides.