Solvent extraction modeling in nuclear fuel cycle reprocessing: speciation of fission products with monoamides - 5116

In this study, a thermodynamic model based on Mikulin and Sergievskii-Dannus equations was developed to model the extraction of water, nitric acid and europium by a monoamide (or N,N-dialkyl-amide) DEHiBA in TPH. Experimental distribution ratios obtained for water, nitric acid and europium were described with a physico-chemical model based on the application of the mass action law on each extraction equilibrium taken into account. The best agreement between experimental and calculated concentrations was obtained by considering the two complexes [L₂Eu(NO₃)₃] and [L₃Eu(NO₃)₃] in organic phase. Speciation in organic phase was also studied by Electro-Spray Ionization Mass Spectrometry (ESI-MS). The stoichiometry of the complexes obtained during the study by ESI-MS and solvent extraction modeling are in very good agreement, suggesting that this spectrometry technique can help to support the modeling of the related separation process. (authors)