'''Uranium''' (U) is a heavy, naturally [[radioactive]], [[metal]]lic [[element]] with an [[atomic number]] of 92. Its two principally occurring [[isotope]]s are uranium-235 and uranium-238. Uranium-235 is indispensable to the nuclear industry because it is the only isotope existing in nature that is fissionable by thermal [[neutron]]s. Uranium-238 is also important because it absorbs neutrons to produce a [[radioactive]] isotope that subsequently decays to the isotope [[plutonium]]-239, which also is [[fission]]able by thermal neutrons. | '''Uranium''' (U) is a heavy, naturally [[radioactive]], [[metal]]lic [[element]] with an [[atomic number]] of 92. Its two principally occurring [[isotope]]s are uranium-235 and uranium-238. Uranium-235 is indispensable to the nuclear industry because it is the only isotope existing in nature that is fissionable by thermal [[neutron]]s. Uranium-238 is also important because it absorbs neutrons to produce a [[radioactive]] isotope that subsequently decays to the isotope [[plutonium]]-239, which also is [[fission]]able by thermal neutrons. |