Tanks in Savannah River (SRS) and Hanford sites contain alkaline high-level waste (HLW) with high concentration of actinides along with Sr, and Cs. An Actinide Removal Process (ARP) is used at SRS to separate Sr and Actinides, while Cs is separated by the Caustic-Side Solvent Extraction technology (CSSX), invented at ORNL. In this project, new organic ligands are proposed that can complex actinides and are compatible with the CSSX solvent system, (and the next-generation NG-CSSX analogous process), for combined Cs and actinide separation from the HLW stream into the organic phase. This modification could lead to improvements in the HLW separation process. The following ligand families are proposed: i) Pyrazolates with softer aromatic N-donor sites; ii) ligands that contain combinations of softer S-sites (sulfoxides) and strongly complexing P-O sites (phosphates); iii) ionizable polysulfonamides with moderate acidity (pK<sub>a</sub> ~ 9-11). Characterization of ligands and/or their metal complexes by NMR, FT-IR and X-ray crystallography will be discussed.

Organic ligands for actinide extraction in alkaline conditions

251st National Meeting (2016)

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