Treatment of High-Level Wastes from the IFR Fuel Cycle

Abstract

The Integral Fast Reactor (IFR)¹ is an advanced power reactor concept sponsored under the U. S. Department of Energy’s reactor development program.² It promises to have important advantages over present reactors in its capability to conserve resources and consume the transuranic elements, thus excluding these from its wastes. It can also be used to consume the actinides in other nuclear wastes, such as spent light-water reactor fuels, and the transuranic (TRU) elements from nuclear weapons. The IFR features on-site reprocessing using pyrochemical methods to recover actinides from the U-Pu-Zr core and U-Zr blanket fuels, separate fission products, and produce suitable high-level waste forms. More than 99% of the TRU elements are recovered and separated from fission products by an electrorefining process at about 500°C.3 Treatment of electrorefiner wastes to recover residual actinides results in the recovery, recycle, and burnup of more than 99.9% of the TRU elements in discharged fuel. The electrorefiner (Figure 1) is a steel vessel that holds a pool of liquid cadmium (which serves as an anode in some operations) and a liquid LiCl-KCl electrolyte. Spent fuel elements are chopped, placed in steel baskets, and immersed in the electrolyte, where the fuel is anodically dissolved from the cladding. A major fraction of the uranium from the fuels is electrochemically deposited on steel cathode rods, and the rest of the uranium and the TRU elements are deposited in liquid cadmium cathodes. A significant fraction of the zirconium is also deposited with uranium on the solid cathodes. These cathodes are retorted to recover salt and cadmium, and melted to produce metal ingots for use in producing new core and blanket fuels.