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An experiment on actinide partitioning from real high level waste (HLW) was performed in a continuous process by extraction with diisodecylphosphoric acid (DIDPA) using a battery of 12 centrifugal extractors installed in a hot cell. The HNO(3) concentration of the HLW was adjusted to 0.5 M by dilution. The extraction section had 8 stages , and H(2)O(2) was added to extract Np effectively. After extraction, Am and Cm were back-extracted with 4 M HNO(3) in 4 stages and Np and Pu were stripped with 0.8 M H(2)C(2)O(4) in 8 stages.
The actinides, except Np, were extracted from HLW with a very high yield. Although only 84% of the Np were recovered in the present experiment, the recovery would be improved to 99.7% by increasing the temperature to 45 C, the number of stages from 8 to 16 and the H(2)O(2) concentration from 1 M to 2 M. Long-lived Tc and the main heat and radiation emitters Cs and Sr were not extracted and were thus separated from the actinides with high decontamination factors.
About 98% of Am and Cm were recovered from the loaded solvent in the first stripping step with 4 M HNO(3). About 86% of Np and about 92% of Pu were back-extracted with 0.8 M H(2)C(2)O(4). These incomplete recoveries would be improved by increasing the number of stages and by optimizing the other process parameters. .

Additional information

Authors: MORITA Y ET AL, Japan Atomic Energy Energy Research Institute, Ibaraki-ken (JP);GLATZ J-P ET AL, JRC Karlsruhe (DE)
Bibliographic Reference: Article: Solvent Extraction and Ion Exchange Vol. 14 (1996) No. 3, pp. 385-400
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