Electrorefining is an electrolytic process that has been used to recover high purity metals (e.g., uranium) from the mixture of elements in used nuclear fuel, also known as spent nuclear fuel. Electrorefining is an electrolytic process carried out in an electrolysis cell in which the impure feed is the anode and the electrolyte is a molten salt of the metal or metals to be recovered mixed with one or more alkali metal salts, with the purified metal being recovered at a metal cathode. The electrorefining process can be used along with electrowinning steps that utilize an additional liquid metal cathode in which metal ions dissolved in the electrolyte are reduced to form an intermetallic with the targeted metal.
Methods based upon fluoride volatility have also been utilized to recover metals from used nuclear fuel. According to this process, metals or metal oxides in the used nuclear fuel are reacted with a fluorinating agent. The fluorinating agent converts the feed materials to a mixture of fluorides, some of which are volatile. The volatile fluorides can then be separated from the remainder of the material and then further separated from each other via adsorption, desublimation, distillation, etc. This method has also been utilized to remove nuclear fuel components from a mixture of molten salts.
U.S. Pat. No. 5,340,447 to Bertaud, et al. describes a process for the selective electrofluorination of a metallic alloy in which a controlled voltage is applied to the alloy. The electrolyte is a mixture of molten fluorides and hydrofluoric acid and a power supply applies a potential to a uranium electrode to selectively oxidate uranium to form volatile UF6. Such systems require energy input and close control of the input currents to maintain the targeted applied voltage across the cell.
What are needed in the art are methods and systems that can selectively recover targeted metals such as uranium from a mixture of components found in used nuclear fuel.