Sigma Team for Minor Actinide Separation FY2011 Annual Report

Abstract

Now finishing its third year of productivity, the Sigma Team for Minor Actinide Separation (STMAS) was formed at the beginning of FY 2009 to perform ground-breaking research laying the basis for more efficient separation methods for americium and other minor actinides (MAs) to greatly improve the overall benefit of fuel recycle. Specific aims of the STMAS are essentially two-fold: to develop the scientific basis for a more robust, more efficient actinide/lanthanide (An/Ln) separation process and to develop the scientific basis for an efficient separation of americium from curium. These two aims are being pursued by integrated hypothesis-driven research mainly within the paradigm of aqueous reprocessing of used oxide nuclear fuel dissolved in nitric acid, with one exception focused on carbonate media. Questions being addressed deal with principles of selectivity through various means including aqueous-phase complexation, use of soft-donor extractants, higher oxidation states of americium, ion exchange, and crystallization/dissolution processes. Explicit attention is also paid to the question of robustness of chemical systems under conditions relevant to future technology implementation. This report outlines the goals of the STMAS, significance of achieving these goals, STMAS organization around the above aims and questions, recent highlights, and future direction.