Uranium 2 Essay, Research Paper

Uranium the 92nd element and a member of Group 3b in the periodic table. Its atomic weight is 238.029. Its name and chemical symbol, U, are derived from Uranus, because that planet was discovered a few years before the discovery of the element. A compound of uranium (uranium oxide) was discovered in a uranium ore, pitchblende, by German chemist M. H. Klaproth in 1789. The German thought that he had found a new element. This was not achieved until 1841, when the French chemist E. M. Peligot reduced uranium tetrachloride with potassium in a platinum crucible to obtain elementary uranium. It was in uranium containing crystals that the French physicist A. H. Becquerel discovered radioactivity in 1896.

Uranium is not as rare as was once believed. Widely distributed in the Earth s crust, it occurs to the extent of about 0.0004 percent, making the metal more plentiful than mercury, antimony, or silver. Before World War2 uranium was of interest as a source of RADIUM for medical use and for producing a yellow, green color in glass and ceramic glazes. Uranium now occupies a key position in nuclear weapons and Nuclear Energy.

Pure uranium is a heavy, silvery white metal that melts at 1,132c and boils at 3,818c. The design of metallic fuel rods for nuclear reactors came from the product of uranium. Uranium is a poor conductor of electricity. It is also soft, although it will harden when machined.

Uranium is a strongly electropositive element. This means that it is easily oxidized. In massive form the metal burns in air at 700c (1,292f). In finely divided form it is pyrophoric that is, it ignites spontaneously in air.

In combining with other chemicals, uranium commonly exhibits one of four oxidation states: +3, +4, +5, and +6. It reacts readily with most nonmetals, dissolves slowly in dilute mineral acids, and dissolves rapidly in oxidizing acids such as nitric acid. An important uranium compound is uranium hexafluoride, which is volatile, and in the absence of water, chemically stable.

Uranium is always found combined with other elements. Ingneous rocks than have uranium exist in the +4 valence state. Because it is large ion it tends not to be included in ferromagnesian minerals that crystallize early in the geochemical process. Instead it becomes concentrated residual liquids during the final stages of crystallization.

When exposed to oxidizing conditions near or at the Earth s surface, most of the time uranium minerals are readily oxidized. Large deposits of this type, which may also contain gold, occur in Canada (43%), South Africa (38%), and

Brazil (19%).

The main uranium ores mines are found in the Blind River area in Ontario, Canada. Vein deposits have also been mined in Canada s Northwest Territories and Saskatchewan, in the Northern Territory of Australia, in Zaire, in France and a little in the United States.

Approximately 90% of the remaining uranium minerals are uranyl compounds. No deposits of concentrated uranium ore have been discovered. As a result uranium must be extracted form ores containing less than 0.1% uranium, so that substantial, complex processing of the ores is required. Usually it is necessary to preconcentrate the ore by grinding and by the flotation process or similar processes.