Research on Actinide Chemistry in Molten Salt

Development of pyroprocess technology and its safeguards technology requires understanding the chemical behaviors of actinides and lanthanides in molten salt at high temperatures and developing chemical analysis methods for nuclear materials of the process. We studied the chemical behaviors of U, Np, and lanthanide ions and their chemical interactions in the molten salt using spectroscopic and electrochemical methods. We constructed a rotating disk electrode system for a high temperature molten salt media and obtained various thermodynamic and electrochemical parameters of actinides and lanthanides. We developed electrochemical and spectroscopic methods to estimate concentrations of uranium and metal ions (up to -9 wt%) in the molten salt for real-time monitoring technology development. We made new systems and technologies to determine molten salt physical properties such as electric conductivity, viscosity, density, and melting point at high temperatures. We enable the electric conductivity measurements of multi-component LiCl-KCl systems containing up to 30 wt% of ions at various temperatures. In particular, our systems had very good reproducibility, which allowed for the production of reliable physical property data, and the modification of a single bubbler afforded a liquid level measurement system at high-temperature environments. In addition, we built a database program (DataChoa) to systematically manage the physical and chemical properties for the molten salt chemistry, and have inputted some of data obtained in this study. We developed chemical analysis methods for various samples produced in the pyroprocess technology development activities. In particular, we validated the bromine-ethyl acetate method and determined the metal/oxide composition of electrochemically reduced SIMFuel at PRIDE. We also set up a shielded ICP-AES system for the analyses of high-level pyroprocess products and salts.