The Back-End Question for Depleted Uranium

Depleted uranium (DU) is uranium primarily composed of the isotope uranium-238 (U-238). DU is useful because of its very high density. Civilian uses include counterweights in aircraft, radiation shielding in medical radiation therapy and industrial radiography equipment, and containers used to transport radioactive materials. Military uses include defensive armor plating and armor-piercing projectiles. A review of present and future situation of DU inventories in the world points out the back-end of the depleted uranium cycle as a future important question: what are the possible destinations of the relatively large quantities of DU produced by the nuclear industry in the past and in the future? An evaluation of the alternatives for the final destination of DU is carried out: recycle and re-use, now and in the future, is one of the options. Immediate use deals with re-enrichment of part of the tails, while future uses may regard the extraction of more LEU (Low-Enriched Uranium), and the use in the fuel cycle of breeder reactors. In all these cases, the implicit store option requires a disposal option that is recoverable. Innovative civil uses of DU in perspective are described in the paper, such as for Spent Nuclear Fuel (SNF) waste packages. This appears to be a valid alternative to the pure waste disposal option: DU has a unique chemical capability for SNF disposal applications (criticality control and suppressing SNF uranium dioxide matrix dissolution). The “waste only” option can foresee seawater dilution (four billion tons of U in equilibrium with the ocean seabed), geological disposal (different European/U.S. requirements for heavy metals), and shallow land burial in the US (with chemical and radiological issues).