(558cf) Optimization of Reduction Cell Efficiency for UO2 to Uranium Metal

Various benefits of closing the nuclear fuel cycle motivate the processing of UO₂ -based spent fuel waste via pyroprocessing techniques. Using pyroprocessing, U and other actinides can be recovered and used to manufacture new nuclear fuel for fast reactors. The reduction of UO₂ is conducted at an elevated temperature (650ºC) in a molten salt (LiCl 1wt% Li₂O). Electrical charge is passed through a cathodic basket containing UO₂ to a platinum anode. In order to achieve the maximum cell efficiency in a reduction cell, the charge needs to go to reducing the UO₂ rather than producing Li metal that subsequently re-oxidizes by reaction with O₂ bubbles. The reduction of Li⁺ ions in the salt can occur at relatively low cathode potential if adequate current cannot be achieved through direct reduction of UO₂. In this study, we found that the value of the cathode potential can indicate whether UO₂ is being directly reduced or metallic Li is being generated. Process variables investigated to promote direct UO₂ reduction and maximize cell efficiency include the use of an anode shroud, the particle size of UO₂, and mesh size of the screen used to contain the UO₂ particles within the cathode basket. Additionally, experimental results are compared between running in constant current or constant cathode potential mode. The extent of reduction of reduced samples for different conditions will be reported as measured via TGA and LECO methods.