Plutonium Third Phase Formation in the 30% TBP/Nitric Acid/Hydrogenated Polypropylene Tetramer System

A study on plutonium third phase formation in 30% TBP/nitric acid/hydrogenated polypropylene tetramer (HPT) was performed. Characterization studies of HPT indicate its composition to be a mixture of many highly branched alkanes with a volatility close to n-undecane. This composition results in about a factor of two better resistance to Pu(IV) third phase formation than dodecane. At 7M nitric acid in the aqueous phase, the presence of Pu(VI) was observed to substantially reduce the organic phase metal concentration necessary to induce phase splitting in both diluents. Spectroscopic investigation of mixed valence systems also suggest a prominent role for Pu(VI) in the formation of the dense organic phase. Accumulation of Pu(VI) in the heavy phase, as well as certain spectral features, suggest that Pu(VI) is Received 22 June 2005, Accepted 31 October 2005 **The views expressed are solely those of the authors and no official support or endorsement of this publication by the Defense Nuclear Facilities Safety Board or the federal government is intended or should be inferred. ***Work performed at Argonne National Laboratory was supported by Duke Cogema Stone & Webster under interagency agreement, through U.S. Department of Energy contract W-31-109-Eng-38. Address correspondence to J. Plaue, Defense Nuclear Facilities Safety Board, 625 Indiana Ave., Washington, DC 20004-290, USA. E-mail: [email protected] Solvent Extraction and Ion Exchange, 24: 271–282, 2006 Copyright # Taylor & Francis Group, LLC ISSN 0736-6299 print/1532-2262 online DOI: 10.1080/07366290600646814