Recovery of Minor Actinides (MA) using a CyMe4-BTBP based SANEX solvent

Efficient recovery of minor actinides from a genuine spent fuel solution has been successfully demonstrated by the CyMe4-BTBP/DMDOHEMA extractant mixture dissolved in octanol. The continuous counter current process, in which actinides(III) were separated from lanthanides(III), was carried out in laboratory centrifugal contactors using an optimised flow-sheet involving a total of 16 stages. The process was divided into 9 stages for extraction from a 2 M nitric acid feed solution, 3 stages for lanthanide scrubbing and 4 stages for actinide back-extraction. Excellent feed decontamination factors for Am (7000) and Cm (1000) were obtained and the recoveries of these elements were higher than 99.9 %. More than 99.9 % of the lanthanides were directed to the raffinate except Gd for which 0.32 % was recovered in the product. In addition the the radiolytic degradation of the CyMe4-BTBP based SANEX solvent has been investigated. As the solvent used in the extraction process is designed to separate trivalent actinides from lanthanides, the radiolytic degradation is mainly due to alpha decay of extracted minor actinide isotopes. A calculation of dose-rates was done by estimating the concentration of minor actinides in the solvent by fuel burn-up calculations and assumptions on dilutions in the subsequent reprocessing steps. Several radiolysis experiments were carried out in order to compare the effect of low LET external gamma radiation (0.2 kGy/h) and internal alpha radiation with different dose-rates (0.05, 0.2 and 1.0 kGy/h). Significant radiolytic degradation was shown in the gamma radiolysis and in the alpha radiolysis experiment at a dose-rate of 1 kGy/h. These experiments were continued up to an absorbed dose ~ 1200 kGy and >300 kGy, respectively. Comparing the alpha radiolysis results for 0.2 kGy/h and 1.0 kGy/h, up to an absorbed dose of ~120 kGy, no significant difference in the degradation for the different dose rates could be seen.JRC.E.5-Nuclear chemistr