Fundamental Chemistry of the Universal Extraction (UNEX) for the Simultaneous Separation of Fission Products and Transurancies from High-Level Waste Streams

Collaborative research by the Idaho National Engineering and Environmental Laboratory and the Khlopin Radium Institute (St. Petersburg, Russia) has already developed and validated the concept of a Universal Extraction (UNEX) solvent for simultaneously removing radioactive strontium, cesium, and transuranics from acidic aqueous waste streams in a single unit operation. These development efforts focused on the application of the process, where extractants were simply evaluated for extraction efficiency. No fundamental data exist on the chemistry of the UNEX solvent or its molecular interactions with extracted metal ions. The objective of this project is to conduct research that experimentally combines classical chemical techniques with advanced instrumental methods to elucidate the mechanisms of simultaneous metal extraction, along with subsequent deployment of Extended X-Ray Absorption Fine Structure (EXAFS) experiments to identify and explain the coordination geometries of extracted metal ions. This project will develop a fundamental understanding of the complicated, synergistic extraction chemistry of the multi-component UNEX extractant. The results will facilitate enhancements to the process chemistry-increasing the efficiency of the UNEX process, minimizing primary and secondary waste streams, and enhancing compatibility of the product streams with the final waste forms--with the global objective of implementing the UNEX process at the industrial scale