Using Depleted Uranium To Shield Vitrified High-Level Waste Packages

For more than 50 years, the U.S. Department of Energy (DOE) has been enriching uranium for commercial nuclear fuel and defense purposes. Natural uranium must be enriched to sustain the fissioning process required for nuclear power production. The uranium enrichment process generates large quantities of depleted uranium (DU) as a byproduct. DU contains less than 0. 7% of its U235 isotope. (The assay of most of the DU in the inventory is 0.2 to 0.5%.) Throughout the DOE complex, there are presently approximately 555,000 metric tons of UF. (375,000 metric tons of uranium metal) in 50,000 cylinders, most of which are stored at the three uranium enrichment sites in l 0-ton and 14-ton steel cylinders (Martin Marietta Energy Systems 1993). Approximately 2,500 ofthese 10- and 14-ton cylinders are added to this inventory annually. Since July l, 1993, the UF. generation has been the responsibility of US Enrichment Corporation. Until the end of the Cold War, DU was being stored by the DOE until it could be used as fuel for breeder reactors, mixed with more highly enriched uranium for reactor fuel, or used as armor protection or armor-piercing penetrators on artillery shells. With the collapse of the Soviet Union and other changes in the geopolitical arena, most of these intended uses are no longer necessary. Rather than direct disposal, alternative uses for the stored DU are being sought by the DOE. End products must be developed that use the specific properties of DU.