The present invention provides a method of simultaneously removing uranium and transuranics from metallic nuclear fuel in an electrorefiner. In the method, a potential difference is established between an anode basket containing the fuel and a solid cathode of the electrorefiner, thereby creating a diffusion layer of uranium and transuranic ions at the solid cathode, a first current density at the anode basket, and a second current density at the solid cathode. The ratio of anode basket area to solid cathode area is selected based on the total concentration of uranium and transuranic metals in a molten halide electrolyte in the electrorefiner and the effective thickness of the diffusion layer at the solid cathode, such that the established first and second current densities result in both codeposition of uranium and transuranic metals on the solid cathode and oxidation of the metallic nuclear fuel in the anode basket.