Electrochemical Oxidation of Americium
There is considerable interest in a closed nuclear fuel cycle in which all process stream materials are either recycled back into power production or transmuted to non-hazardous stable isotopes which can be disposed in ordinary ways. One impediment to this process is the presence of minor actinide and lanthanide metals, both, in the waste. The minor actinides could be separated from the mixture and either (i) recycled into power generation, or (ii) transmuted via neutron bombardment to non-hazardous stable elements. Separating the actinides from the lanthanides is essential because the lanthanide metals also absorb neutrons and block the process. However it is very challenging because of similarity in size and charge of the two classes of metals. Ligands that selectively bind to actinides in the presence of lanthanides, and permit their extraction, have been demonstrated. We are investigating the cause of the ligand selectivity. Our hypothesis is that increased covalency of ligand-metal bond enhances the selective coordination of americium. We are studying a series of lanthanides and actinides to test this hypothesis and if successful this work would lead to improved separation techniques. We employ electrochemical methods to generate unusual oxidation states of americium and the lanthanides, in order to put them all into the same oxidation state. This permits direct comparison of ligand-to-metal binding under the same conditions of size and charge, and allows the effect of ligand covalency to be isolated. Ligand covalency can be measured via raman spectroscopy. We will present the results of this work.