Nuclear power generation will continue to have a role in the United States total energy production in the forseeable future, and whether or not that role continues, the legacy waste from nuclear power generation will need to be remediated. Long term storage options are no longer seriously considered. The Purex and other processes for removing uranium and plutonium from aqueous wastes are very successful and most of the remaining radioactivity of the wastes is due to americium and curium (minor actinides, "MAs"). Their removal is complicated by similarity in size, charge, surface charge density, and reactivity to the lanthanides which are also present and which can prevent the transmutation of these MA isotopes to stable elements. Therefore the long term goal of this project is to develop an extraction method for the elements americium and curium. This project will use a ligand designed by Idaho National Laboratory (a polyfluoridated dithiophosphinic acid) to selectively extract minor actinides from a mixture containing the lanthanides as well. The hypothesis is that the minor actinides favor more covalency in coordination (i.e. softer donor atoms), while the lanthanides favor more ionicity in the coordination sphere. A trend in donor preference is expected across the actinide series, from actinium through curium, from greater ionicity of the coordination bond, to greater covalency. To demonstrate such a trend it is desirable to include as many elements in the series as we can. Therefore we will use thorium and uranium in addition to the MA's. These two elements favor higher oxidation states than the MAs therefore they must be reduced to include them in the series, so that charge is not a differentiator in the strength of the ligand-metal bond. The reduction of uranium in aqueous solution has proven to be challenging. We seek to characterize the reduction of uranium using a specially designed electrochemical cell in which U(III) can be generated electrochemically. Studying the thermodynamics and kinetics of the reduction process will enable us to define a protocol for generation and stabilization of the uranium(III) ion in acidic aqueous solution. Progress in reduction of uranium(VI) to uranium(III) will be reported.

Electrochemical reduction of aqueous uranium

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.