Depleted uranium is uranium that has had some of its U-235 content removed.
Over the last four decades, large quantities of uranium were processed by gaseous diffusion to produce uranium having a higher concentration of uranium-235 than the 0.72% that occurs naturally (called "enriched" uranium) for use in U.S. national defense and civilian applications. "Depleted" uranium is also a product of the enrichment process. However, depleted uranium has been stripped of some of its natural uranium-235 content. Most of the Department of Energy's (DOE) depleted uranium inventory contains between 0.2 to 0.4 weight-percent uranium-235, well below levels necessary to create a nuclear chain reaction.
Any uranium compound (e.g., UF6, UF4, U3O8) can contain "enriched" or "depleted" uranium. Because the enrichment process used in the United States utilizes uranium hexafluoride (UF6), the depleted uranium product produced is depleted uranium hexafluoride (depleted UF6). Management of DOE's inventory of depleted UF6 is the responsibility of the DUF6 Management Program.