Results of recent counter-current tests on An(III)/Ln(III) separation using TODGA extractant
Résumé
One of the different options investigated at the CEA Marcoule to separate trivalent minor actinides (An(III) = Am(III) to Cf(III)) directly from PUREX raffinates by solvent extraction takes advantage of both the high efficiency of the diglycolamide, N,N,N',N'-tetraoctyldiglycolamide (TODGA), to extract trivalent 4f and 5f elements from nitrate containing aqueous solutions, and the selectivity of hydrophilic polyaminocarboxylic acids, which better complex trivalent 5f elements than 4f elements in buffered conditions, and hence allow the former elements (An(III)) to be selectively stripped, whereas the latter elements (Ln(III)) remain in the solvent and are further back-extracted in diluted nitric acid. The major difficulty of this separation process is to tune the pH in a very narrow range of operating conditions, at the An(III) selective stripping step, because of the high sensitivity of the performances of the flowsheet. The extraction system was optimized to meet the requirements of an efficient process flowsheet allowing recovery yields greater than 99.9% to be obtained for the An(III), with high decontamination factors vs Ln(III), in only one cycle after the PUREX process implementation. A cold test was successfully carried out in small scale mixer-settlers in the Marcel testing loop, using a surrogate feed composed of major fission products. A medium activity test was further implemented in similar laboratory contactors, in the glove boxes of the ATALANTE facility, on a surrogate feed spiked with Am-241, Cm-244, and Eu-152. This paper describes the results of these two counter-current tests.
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