Role of diluents in the comparative extraction of Th(IV), U(VI) and other relevant metal ions by DHOA and TBP from nitric acid media and simulated wastes: Reprocessing of U–Th based fuel in perspective

• DHOA (di-n-hexyloctanamide) has been evaluated as an extractant in Solvesso 100 and Shell sol D70, comparing with TBP.
• The reprocessing of Th-based fuels (AHWR) revovery of Th and extraction of U(VI) in the presence of Th.
• Some interesting trends in the acid uptake and distribution ratios of metal ions
• A simulated HLW solution was treated with both extractants

Keeping reprocessing of 233U–Th based fuel in perspective, solvent extraction of Th(IV), U(VI) and some relevant metal ions has been carried out from nitric acid media and simulated high-level waste (HLW) typical of a fast-breeder reactor using dihexyloctanamide (DHOA) in commercially available alternate diluents, viz. Solvesso 100 and ShellSol D70. Acid uptake constant (KH) and distribution ratios (D) of metal ions as a function of nitric acid, thorium ion and extractant concentrations are determined. Slope-analysis results showed various types of species extracted into the organic phase. For comparison, a similar set of experiments were carried out with tri-n-butyl phosphate (TBP) in both diluents. A few clear and interesting trends were observed in the variation of D values of metal ions. Interference of other relevant metal ions likely to get co-extracted along with Th(IV) and U(VI) was also studied by ICP-AES using a simulated HLW.

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