Worlds of David Darling
Encyclopedia of Science
   
Home > Encyclopedia of Science

uranium (U)





uranium
A billet of highly enriched uranium recovered from scrap processed at the Y-12 Facility in Oak Ridge, TN. Credit: US Dept of Energy
A heavy, soft, silvery-white, metallic element, radioactive, easily oxidized, and having 14 known isotopes of which 238U is the most abundant in nature. Uranium is in the actinide series. It occurs in several ores, including pitchblende, uraninite, and carnonite, from which it is extracted and processed for use in research and nuclear fuels.

The naturally occurring isotopes are fissionable 235U (0.7205% of natural uranium), 238U which cannot be fissioned with thermal neutrons (99.2739% of natural uranium), and 234U, a decay product of 238U (0.0056%). Enriched uranium is that in which the percentage of the fissionable isotope 235U has increased beyond the content of 0.7205% of natural uranium. Depleted uranium has a lower percentage of 235U than that occurring in natural uranium; it is produced during uranium isotope separation.

The decay of uranium yields a series (see radioactive series) of radioactive products, including radium and radon. Exposure to the radiation emitted by uranium can cause tissue damage or cancer. Uranium is also chemically poisonous and can cause damage to the urinary system.


atomic number 92
relative atomic mass 238.03
melting point 1,132°C (2,070°F)
boiling point 3,818°C (6,904°F)
relative density 18.95


Related categories

   • ATOMIC AND NUCLEAR PHYSICS
   • INORGANIC CHEMISTRY