Uranium is used in the production of nuclear energy, for peaceful uses as well as bombs. In 2007, 37,600 metric tonnes of uranium were produced.
Physical properties: In its pure form, uranium is a silvery-white metal. Uranium is 70% denser (19.10 gram/cm3) than lead, but not as dense as gold and tungsten. The metal is quite hard (6.0 out of 10 point scale), malleable, ductile and slightly paramagnetic. Uranium melts at 1132C, and boils at 4131C. Naturally occurring uranium is mostly of the U-238 type, which is weakly radioactive and emits alpha-radiation in a low dose. Mixed with it, however, is a small fraction of U-235. U-235 is unstable. When bombarded with neutron particles, U-235 splits into smaller atoms and releases immense amounts of energy. This energy can be used to generate power, or it can be used to make an "atomic bomb".
Powdered uranium is a fire hazard, as the small grains catch fire very easily.
Chemical properties: Uranium reacts with many non-metal elements such as oxygen, hydrogen, carbon, nitrogen and the halogens (fluorine, chlorine, bromine, iodine). Powdered uranium reacts with cold water, and when it is exposed to air it develops a thin layer of dark uranium oxide on the surface.
History: Uranium has been used since 79 AD to put a yellow color on ceramic glazes. It was used in Ancient and Roman times for coloring glass. Uranium was discovered in 1789 by German chemist Martin Heinrich Klaproth (1743-1817) while he was working in his laboratory in Berlin. Klaproth reacted uranium ore (uraninite) with nitric acid, then heated the remainder with charcoal. He thought the powder he had produced was a new element, and named it after the planet Uranus. However, the powder he was left with turned out to be uranium oxide, and only in 1841 did the French chemist Eugène-Melchior Péligot (1811-1890) manage to isolate pure uranium in his laboratory. In the 19th century, most of the world's uranium came from old silver mines in the area now known as the Czech Republic. In 1896, the physicist Antoine Henri Becquerel (1852-1908) discovered the radioactivity of uranium. He left a piece of uranium on a photographic plate, and when he came back, the photographic plate had become cloudy, or "fogged" as he described it. He realized that uranium must be giving off invisible rays (turned out to be alpha radiation) that altered the appearance of the plate. Research on uranium continued in the 20th century, mainly with the purpose of building atomic bombs. Two such bombs were dropped on Hiroshima and Nagasaki towards the end of World War II. Current research on uranium focuses more on its use to generate power in nuclear reactors.
Production: Uranium can be mined in several ways, including open-pit and underground mining. The uranium content in uranium ores varies greatly. While some ores (like uraninite) contain up to 70% uranium oxide, poor quality ores contain just 0.01-0.25% uranium. Uranium ores are converted to oxide, and then to fluoride. Uranium fluoride is reduced (i.e. the fluorine is removed) with magnesium or calcium to produce pure uranium. Uranium is often recycled, which adds back to our supply of the metal. The top five producers of uranium are Canada, Australia, Kazakhstan, Russia and Namibia. Pie Chart of Top 5 Uranium Producing Countries...
Uses: Before people became aware of the radioactivity of uranium, they used the metal to color glass yellow and in pottery glaze. Uranium chemicals were also used in photography.
Today, uranium rich in the U-235 variety is used to produce nuclear energy. One kilogram of U-235 can generate the same amount of power as 1,500 tonnes of coal. Power-generating nuclear reactors can use uranium with 3-5% U-235 to generate energy steadily, but nuclear weapons often use uranium with up to 90% U-235 content. The high level of U-235 in nuclear weapons causes a runaway "fission" (atom-splitting) reaction that releases tremendous energy in the form of a nuclear blast. This is how the "Little Boy" atomic bomb dropped on Hiroshima killed 140,000 people on Monday, August 6, 1945.
Uranium is dense, hard and flammable, and is used to make both military armor as well as weapons that can pierce such armor. The residue from uranium weapons are radioactive and cause serious damage to health.
Health: A person can be exposed to uranium by inhaling uranium dust in the air, or by eating or drinking contaminated substances. People working in environments where uranium is used are at greater risk. If eaten, only a small part of uranium is digested, but that itself is highly toxic. Inhaled uranium settles in our lungs and causes problems to our respiratory system. Inhaled or ingested uranium cause the kidney, brain, liver and heart to function abnormally. Tests on animals in laboratories show that uranium damages the immune system and causes birth defects in babies. The same effects seem likely when humans are exposed to uranium.
Jackson, Tom. Radioactive elements, 2006, Marshall Cavendish, USA.
Uranium, Wikipedia. <http://en.wikipedia.org/wiki/Uranium> accessed on 22-Feb-2009.
ToxFAQs for Uranium, ATSDR (Agency for Toxic Substances and Disease Registry). http://www.atsdr.cdc.gov/tfacts150.html> accessed on 22-Feb-2009.