Promising Pyrochemical Actinide/Lanthanide Separation Processes Using Aluminum

Thermodynamic calculations have shown that aluminum is the most promising metallic solvent or support for the separation of actinides (An) from lanthanides (Ln). In molten fluoride salt, the technique of reductive extraction is under development in which the separation is based on different distributions of An and Ln between the salt and metallic Al phases. In this process molten aluminum alloy acts as both a reductant and a solvent into which the actinides are selectively extracted. It was demonstrated that a one-stage reductive extraction process, using a concentrated solution, allows a recovery of more than 99.3% of Pu and Am. In addition excellent separation factors between Pu and Ln well above 10³ were obtained. In molten chloride media similar separations are developed by constant current electrorefining between a metallic alloy fuel (U₆₀Pu₂₀-Zr₁₀Am₂Nd_3.5Y_0.5Ce_0.5Gd_0.5) and an Al solid cathode. In a series of demonstration experiments, almost 25 g of metallic fuel was reprocessed and actinides collected as An-Al alloys on the cathode. Analysis of the An-Al deposits confirmed that an excellent An/Ln separation (An/Ln mass ratio = 2400) had been obtained. These results show that Al is a very promising material to be used in pyrochemical reprocessing of actinides.