J.D. Einkauf, J.M. Pyles, M.E. Lamb, L.R. Sadergaski, H.M. Meyer, L.H. Delmau, B.A. Moyer, J.D. Burns
Oak Ridge National Laboratory,
United States
Keywords: ruthenium, oxidation, used nuclear fuel
Summary:
Ruthenium presents a significant challenge in used nuclear fuel (UNF) reprocessing due to its complex redox behavior, variable speciation in nitric acid, partial extractability, and volatility. Here, we demonstrate a strategy for selective Ru removal through volatilization of RuO4 using a strong oxidant, followed by deposition onto various substrates. Polymer-based substrates, particularly polyolefin wax film, showed superior performance, achieving up to near-quantitative Ru removal from solution, and after dissolution of the substrate, 99.6% of the Ru was recovered as RuO2. Mechanistic studies show that Ru deposition on these polymers involves both physisorption and oxidative reactions with the polymer, whereas inorganic substrates only support physisorption. This approach remains effective under conditions of simulated oxidation of UNF solutions, selectively removing Ru while leaving other fission products in solution. This method offers a practical and efficient strategy for ruthenium decontamination and recovery, offering a route for integration into existing UNF reprocessing flowsheets to enhance overall process safety and performance.