TEHDGA, DMDOHEMA and Mixed Sorbents: Characterization and Am(III) Uptake Properties

The Atalante research facility produces radioactive waste that have to be managed according to specific rules. In particular, solid and liquid wastes need to be transferred to another facility in Marcoule to be evaporated with an alpha activity limit of 16.65 GBq/m3. The radioactive aqueous nitric acid wastes produced in Atalante must be first decontaminated by removing U, Pu and minor actinides and therefore a dedicated decontamination program for radioactive aqueous nitric acid wastes is implemented in Atalante. In particular, the recovery of americium and curium is obtained by extraction chromatography. TEHDGA (N, N, N', N'-tetra-2-ethylhexyl-3-oxopentane-1,5-diamide), DMDOHEMA ((N,N'-dimethyl-N,N'-dioctylhexyloxyethyl malonamide) and a mixture of both extractants were impregnated on silica gel and studied.Batch experiments were made to determine the performances of such a process. The weight distribution coefficients (Dw) were determined for Am and Nd. Different kinetic behavior was found with both complexants. An effect of nitric acid concentration was observed. For three solids, the americium's uptake increases with acidity. Loading capacities by isotherm and Langmuir isotherm are obtained (between 48mg.g-1 and 94mg.g-1). After determining various parameters in batch extraction experiments, the performances of the solid supports were studied in columns. The breakthrough and elution curves were obtained with neodymium (respectively between 12mg.g-1 and 21mg.g-1; 0.17 and 0.27 L.g-1). Capacity and recovery were optimized with the mixture of DMDOHEMA and TEHDGA.