Actinide, lanthanide, and fission product speciation and electrochemistry in ionic melts

We report the results of recent research that we have undertaken to increase our understanding of key actinide and fission product speciation in a range of ionic melts. These results will be used to develop novel electrochemical methods of separation of uranium and plutonium from irradiated nuclear fuel. Our studies in high temperature alkali metal melts (including LiCl and the eutectics LiCl-KCl and CsCI-NaCl) have focussed on in-situ speciation of U, Tc and Ru using both Electronic Absorption Spectroscopy (EAS) and X-ray Absorption Spectroscopy (XAS). The XAS studies have included Extended X-Ray Absorption Fine Structure (EXAFS) and X-Ray Absorption Near Edge Structure (XANES) measurements. We report what could be unusual uranium speciation in high temperature melts and evaluate the likelihood of Ru or Tc volatilisation during plant operation. Our studies in lower temperature melts, commonly known as ionic liquids, have focussed on salts containing tertiary alkyl group 15 cations and the bis(trifluoromethylsulphonyl)imide anion, melts which we know to have exceptionally wide electrochemical windows. We report Ln, Th, U and Np speciation (XAS, EAS and vibrational spectroscopy) and electrochemistry in these melts.