In military applications, when alloyed, Depleted Uranium [DU] is ideal for use in armor penetrators. These solid metal projectiles have the speed, mass and physical properties to perform exceptionally well against armored targets. DU provides a substantial performance advantage, well above other competing materials. This allows DU penetrators to defeat an armored target at a significantly greater distance. Also, DU's density and physical properties make it ideal for use as armor plate. DU has been used in weapon systems for many years in both applications.Depleted uranium results from the enriching of natural uranium for use in nuclear reactors. Natural uranium is a slightly radioactive metal that is present in most rocks and soils as well as in many rivers and sea water. Natural uranium consists primarily of a mixture of two isotopes (forms) of uranium, Uranium-235 (U235) and Uranium-238 (U238), in the proportion of about 0.7 and 99.3 percent, respectively. Nuclear reactors require U235 to produce energy, therefore, the natural uranium has to be enriched to obtain the isotope U235 by removing a large part of the U238. Uranium-238 becomes DU, which is 0.7 times as radioactive as natural uranium. Since DU has a half-life of 4.5 billion years, there is very little decay of those DU materials.