High Temperature Electrochemistry IV: Session II
Sponsored by: TMS Extraction and Processing Division, TMS: Nuclear Materials Committee, TMS: Hydrometallurgy and Electrometallurgy Committee
Program Organizers: Prabhat Tripathy, Batelle Energy Alliance (Idaho National Laboratory); Guy Fredrickson, Idaho National Laboratory
Tuesday 8:30 AM
March 16, 2021
Room: RM 40
Location: TMS2021 Virtual
Session Chair: Vasant Kumar Ramachandran, University of Cambridge
8:30 AM
Electrochemical Reactions of Oxide Ions with Tungsten in Molten CaCl2: Chao Zhang1; Devin Rappleye1; Michael Simpson2; 1Lawrence Livermore National Laboratory; 2University of Utah
In support of development of a real time electrochemical sensor for measuring oxide ion concentrations in molten CaCl2, cyclic voltammetry was run in molten CaCl2 with controlled additions of CaO. The magnitude of an oxidation peak at close to 0 V versus a W quasi-reference electrode correlated linearly with concentration of added CaO. The reaction mechanism appears to consist of two electrochemical steps followed by a chemical reaction to form CaWO4, which is soluble in the salt. These findings are beneficial to controlling electrochemical nuclear material processing such as direct oxide reduction of actinides. A simple probe consisting of three W rods can be used to monitor CaO concentration in real time.
9:00 AM
Optimizing Reaction Selectivity in High Temperature Molten Electrolytes: Mary Elizabeth Wagner1; Antoine Allanore1; 1Massachusetts Institute of Technology
Achievement of a high-purity metal product during electrolysis is a challenge faced by both primary processing and recycling industries. Determination of what species will be reduced at the cathode is often limited to standard-state thermodynamics and trial-and-error experimentation. This approach hinders development of new electrolytes by requiring large amounts of data to be gathered before practicality can be determined. However, in high-temperature processes where both the metal product and the electrolyte are molten, the thermodynamic behavior of the electrolytic cell as well as the liquid-liquid equilibria established will heavily influence which metal is reduced and if any co-deposition will occur. By modeling this equilibrium, novel electrolytes can be screened for feasibility. Furthermore, knowledge of the cathode-electrolyte equilibrium can be used to optimize cell performance by tailoring the use of additives and supporting electrolytes.
9:30 AM
Fundamental Challenges for the Development of Electrolytic Reduction of Uranium Oxide in Molten LiCl-Li2O
: Jarom Chamberlain1; Adam Burak1; Mario Gonzalez1; Michael Simpson1; 1University of Utah
Electrolytic uranium oxide reduction has the potential to be a process for recycling spent fuel from commercial light water reactors to advanced nuclear reactors—including molten salt reactors and metal fueled reactors. However, several problems with the process have been identified that need to be addressed to support efficient, cost-effective commercial implementation. Process optimization requires attention to corrosion, anode stability, cell efficiency, and cathode product purity. Generation of oxygen bubbles at the anode combined with high temperature (650oC) and molten chloride salt (LiCl + 1 wt% Li2O) create an oxidizing environment for metals needed for salt containment and shrouding the anode. Methods for removing water and hydroxides from the salt will be reported that improve cell efficiency. Uranium oxide can be reduced chemically by reaction with electrochemically generated lithium atoms or electrolytically with direct reduction of UO2. The reduction mechanism also affects the buildup of entrained lithium oxide.
10:00 AM
New Electrochemical Deoxidation Method of Ti Metal in Molten Salts Containing YCl3: Akihiro Iizuka1; Takanari Ouchi1; Toru Okabe1; 1The University of Tokyo
Technologies for removing oxygen (O) directly from titanium (Ti) scrap are highly important from an industrial view point. In our previous study, a thermochemical deoxidation method of Ti using Y metal in YCl3 (l) was developed. We demonstrated that Ti with an extremely low O concentration (30–60 ppm O) can be reliably obtained utilizing the Y/YOCl/YCl3 equilibrium. To further decrease O contamination in Ti, in this study, an electrochemical deoxidation method was designed and investigated in molten salts containing YCl3 (l). The set-up consists of a Ti anode and a graphite cathode. This method can be applied for semi-continuous deoxidation of Ti and has a high tolerance for O contamination during the process. The establishment of this method is expected to promote the efficient recycling of Ti scrap in the future.