(393e) Elucidation Of Bubble Size Distribution In A Mock-Up Experiment For An Oxide Reduction Electrochemical Cell

Herrmann, S., Idaho National Laboratory
Li, S. X., Idaho National Laboratory

Sodium bonded metallic fuel was used in Argonne's EBR-II reactor. To improve this operation, a pyrochemical treatment process was designed to reprocess the fuel under the Integral Fast Reactor program and later to treat the fuel for disposal in Yucca Mountain under the EBR-II Spent Fuel Treatment Program. In this process, (1) fuel is anodically dissolved in molten LiCl-KCl-UCl3, (2) pure U deposits on a solid cathode mandrel and (3) sodium, active metal fission products, and TRU's are oxidized and accumulated in the molten salt as chlorides. Durable waste forms are generated to immobilize the fission products. Noble metals and cladding hulls remain in anode baskets and are converted into a metal waste form while active metals accumulate in the salt which is converted into a ceramic waste form by mixing with zeolite and glass. In order to extend this technology to be useful for treating advanced oxide fuels, which are being considered for various Generation-IV reactor concepts, a head-end process is needed to convert the oxides to metals. This is referred to as oxide reduction.

Despite extensive research and development of the oxide reduction process, there is a still a concern regarding the generation of oxygen bubbles around the anode which potentially lowers the cell efficiency. Therefore, the goal is to study the effect of physical properties and electrochemical variables on bubble size distribution for gas-liquid interaction in this electrolytic reduction process. To theoretically predict and experimentally assess this problem, a fundamental mock-up study for this process has been designed to focus on the effect of continuous phase viscosity on the bubble sizes. Oxygen bubbles were generated using the electrochemical process on a Pt anode at different variable rates in various aqueous glycerol solutions. Data were acquired at 500 frames per second using a high-speed imaging system. Results will be discussed.