Extraction behavior of actinides and lanthanides in a molten fluoride/liquid aluminum system

As one of the basic investigations on the group partitioning of actinides and lanthanides by a pyrochemical reductive extraction process, the distribution ratios of Pu, Am, Ce and Sm have been experimentally determined in the binary liquid LiF-AlF3/Al-Cu system at the temperature of 830 °C. The distribution ratios of Pu and Am are much larger than those of Ce and Sm. They would allow a high recovery yield of the actinides and good separation factors with lanthanides. The influence of the salt composition (LiF/AlF3 ratio) on the distribution coefficients has been investigated. Coupling the obtained experimental results and literature data, a thermodynamic model that describes the extraction in terms of Gibbs enthalpies of formation and the fluorobasicity of the melt (pF) has been developed. The activity coefficients of Sm(+II) et Ce(+III) versus the pF have been infered: they clearly reveal the difference in solvation behavior between divalent and trivalent species.