2, University of Virginia, Charlottesville, Virginia, United States
The management of waste products generated during the recycling of spent nuclear fuel remains an important consideration in the development of processes such as pyroprocessing. We describe here the application of ion-selective ceramics as electrochemical filters for the separation of fission product waste from molten salt electrolytes used in spent nuclear fuel recycling. As part of a larger emphasis on separation and recycling of spent nuclear fuel, pyroprocessing allows for the electrochemical separation of recyclable actinides from waste fission products (FPs). In the course of this process, high-heat generating contaminants such as Cs+ or Sr2+ remain dissolved in the eutectic chloride molten salt electrolytes used for actinide separation. Removal of such short-lived, high heat-generating FPs is an important objective in the consolidation of radioactive waste and is key to recycling the LiCl-KCl molten salts. Here, we explore an electrochemical approach designed around the use of ion-conducting ceramics to selectively separate Cs+ and Sr2+ from LiCl-KCl eutectic molten salts. We will describe a ceramic-mediated scheme for ion filtration that relies on the selective transport of ions through designed solid state ion conductors, based on ionic size and ionic charge. Having demonstrated the feasibility of this approach in high temperature molten LiCl-KCl-based salts, we discuss the stability and performance of selective garnet-based and NaSICON-based ceramic ion conductors in electrochemically isolating Cs+ from a mixed salt melt. In addition to potentially improving the recycling of spent nuclear fuels, this ceramic-mediated approach to chemical separations may impact additional technologies ranging from energy storage to advanced chemical purification.
Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.