Uranium-238, also known as Depleted Uranium and 238U, is the most common uranium isotope that is naturally occurring. It is an unstableCitation Needed isotope, which accounts for approximately 99.284% of naturally occurring uranium isotopes. It is also used in warfare, for depleted uranium materials such as artillery ammunition, and tank armor. If it is hit by a neutron, It turns into Uranium-239, which decays into Plutonium-239. Uranium-238 decays, itself, by means of Alpha decay. "In a fission nuclear reactor, uranium-238 can be used to breed plutonium-239, which itself can be used in a nuclear weapon or as a reactor fuel source. In fact, in a typical nuclear reactor, up to a third of the generated power does come from the fission of plutonium-239, which is not supplied as a fuel to the reactor, but transmuted from uranium-238."