Mechanical Engineering Journal (Mar 2024)
Performance comparison of monoamides on U recovery by temperature swing extraction using Ce
Abstract
Nuclear fuel fabrication process has generated a large amount of wastes contaminated with enriched uranium, and those have been accumulated for long time in Japan. These waste hasn’t treated, because there is no protocol to treat and dispose these. Procedure is proposed; 1) Leaching Uranium from the waste, 2) recovering uranium from the leaching solution, 3) treating residue and secondary waste for disposing in the near field region. As concentration of uranium in the leaching solution must be far smaller than that of dissolving solution of the spent fuel, an efficient uranium recovery procedure which generates less secondary wastes than the solvent extraction technology is required. Temperature swing extraction technology is one of promising methods to recover uranium efficiently. In the technology, uranium ions are extracted by extraction, and complex with ligands are separated by a polymer with reversible hydrophilic-hydrophobic properties. Monoamides can be adopted to the procedure. However suitable structure of monoamide for the technology is unclear. Therefore, for deciding appropriate structure of monoamides, these with different alkyl chain structures were synthesized, and applicability of the extractants were evaluated by solvent extraction and temperature swing extraction experiments. In experiments, Ce(IV) was used as a simulant of U(IV). Three monoamides were synthesized, and solvent extraction experiments and Temperature swing extraction experiments were carried out. Monoamides with straight chain showed larger recovery ratios whereas the branching monoamide showed far smaller values on solvent extraction experiments, and separation factors of Ce was good on monoamides with straight chain on temperature swing extraction experiments. Therefore the monoamide with long straight chain can be favorable for uranium recovery.
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