Non-Aqueous Electrochemical Fluorination of Used Nuclear Fuel as an Advanced Separation Process

• Published in: Journal of the Electrochemical Society Vol. 166; no. 8; pp. E231 - E239
• Main Authors: Martínez-Rodríguez, Michael J., Olson, Luke C., Gray, Joshua R., García-Díaz, Brenda L.
• Format: Journal Article
• Language: English
• Published: United States The Electrochemical Society 2019
• Subjects: electrochemical engineering; FLiNaK; galvanic cell; molten salts; NUCLEAR FUEL CYCLE AND FUEL MATERIALS; uranium hexafluoride
• ISSN: 0013-4651; 1945-7111
• DOI: 10.1149/2.0261908jes

Development of efficient and environmentally benign methods to reprocess used nuclear fuel (UNF) will enable technologies for a nuclear renaissance. Electrochemical and fluorination methods for reprocessing UNF have been proposed, but combinations of electrochemical and fluorination methods have not been investigated. Electrochemical fluorination may reduce waste volumes compared to the main large-scale aqueous methods for processing used nuclear fuel. In this work, a non-aqueous electrochemical fluorination reprocessing method has been developed and demonstrated that enables gas phase uranium recovery while allowing for potential control of the reaction using a single process. Thermodynamic modeling showed a galvanic reaction between UNF and a fluorinating agent, such as NF3, in a molten fluoride electrolyte was possible and could selectively fluorinate U to UF6. To verify the model results, a reactor system for electrochemical fluorination was constructed along with vessels for product collection and analysis. Initial trials of the electrochemical reaction were performed and characterized by several electrochemical methods. The electrochemical oxidation of U using NF3 as an oxidizing agent was demonstrated and UF6 as a reaction product was detected.