Improving Americium/Curium\nSeparation Factors in the\nAmSel Process through Symmetry Lowering of the Diglycolamide Extractant

Partitioning and transmutation are important strategies\nfor closing\nthe nuclear fuel cycle. The diglycolamide extractant TODGA has played\na major role in the development of solvent extraction processes for\nnuclear fuel reprocessing due to its good extraction performance,\nits hydrolytic and radiolytic stability, and its compliance with the\nCHON principle. However, due to drawbacks such as the tendency to\nform a third phase during extraction if no phase modifiers are used,\ncontinued research on diglycolamide-type extractants has led to the\ndevelopment of diglycolamides with decreased symmetry. In this study,\nit is shown that the recently developed diglycolamide, <i>N</i>,<i>N</i>-diisopropyl-<i>N</i>′,<i>N</i>′-didodecyldiglycolamide (iPDdDGA), is a potential\nalternative to TODGA with improved separation between Am and Cm or\nthe Ln. Using the AmSel system as a reference, the extraction kinetics,\ninfluence of the acid concentration, influence of the iPDdDGA concentration,\nand influence of temperature were evaluated. Slope analysis indicates\nsimilar average stoichiometries for iPDdDGA and TODGA complexes, but\nthe extraction efficiency of iPDdDGA is orders of magnitude higher.\nThe feasibility of selective americium stripping in combination with\nthe hydrophilic sulfonated bis-triazinyl bipyridine SO<sub>3</sub>-Ph-BTBP complexant was demonstrated. Selective stripping of americium\nwas found to be possible, and the use of iPDdDGA gave an unexpected\nimprovement in Am/Cm separation, with SF<sub>Cm/Am</sub> values of\nup to 3.0. This represents a small but significant improvement compared\nto the 2.5 value typically found for TODGA, and it demonstrates the\npotential of this solvent extraction system to improve existing processes\nbased on diglycolamide-type extractants.