Actinide, lanthanide, fission product speciation and electrochemistry

There is currently a great deal of research interest in the development of molten salt technology, both classical high temperature melts and low temperature ionic liquids, for the electrochemical separation of the actinides from spent nuclear fuel. We are interested in gaining a better understanding of actinide and key fission product speciation and electrochemical properties in a range of melts. Our studies in high temperature alkali metal melts (including LiCl and LiCl-KCl and CsCl-NaCl eutectics) have focussed on in-situ species of U, Th, Tc & Ru using X-ray absorption spectroscopy (XAS, both EXAFS and XANES) electronic absorption spectroscopy (EAS) and Raman spectroscopy. We report unusual actinide speciation in high temperature melts and an evaluation of the likelihood of Ru or Tc volatilisation during plant operation. Our studies in lower temperature melts (ionic liquids) have focussed on salts containing tertiary alkyl group 15 cations and the bis(trifluormethyl)sulfonyl)limide anion, melts which we have shown to have exceptionally wide electrochemical windows. We report Ln, Th, U, Np and Pu speciation (XAS, EAS and vibrational spectroscopy) and electrochemistry in these melts and relate the solution studies to crystallographic characterised benchmark species.