Stephen McCrady, age 12, of Nashville, Tenn., for his question:
WHO DISCOVERED URANIUM?
Uranium is the main source of nuclear energy, produced by the splitting of atoms. Uranium was discovered in 1789 by a German chemist named Martin Heinrich Klaproth. He found an oxide of uranium in the mineral pitchblende.
Klaproth named the new element in honor of the discovery of the planet Uranus. The element was not isolated until 1842, however.
Uranium is not a rare mineral. It is more common in the earth than such so called common elements as mercury, silver and iodine. But the concentration of uranium in most rocks is only a few parts in a million.
The richest uranium ore, pitchblende, contains uranium oxides. It is a dark bluish black mineral with a pitchlike luster. The most important ore found in the United States is carnotite, a compound of uranium with vanadium, potassium and oxygen.
Due to its importance as a source of nuclear energy, uranium has been vigorously sought since the end of World War II. Experts estimate that there are more than 1 million tons of uranium ore in non Communist countries that could be mined.
Large amounts of uranium also exist in shale and phosphate deposits, in granites and in the ocean, but these cannot be recovered at a reasonable cost.
Leading uranium producing country is the United States, followed by Canada, South Africa, France, Niger, Gabon and Spain.
Leading uranium producing state or province is Wyoming, followed by New Mexico, Ontario, Texas, Colorado, Utah and Saskatchewan.
Uranium ore goes from the mines to uranium concentrating plants. There, impurities are removed and the uranium is converted into an oxide of uranium. Then, in other plants, the uranium oxide is refined to either a metal powder of pure uranium or the compound uranium hexafluoride.
Uranium has the highest atomic weight of any element found in nature. Its atomic number is 92 and its atomic weight is 238.03. Uranium is radioactive, which means that it gives off nuclear particles.
The metal powder of pure uranium may be used in nuclear reactors to produce plutonium. The compound uranium hexafluoride goes to gaseous diffusion plants. There, the compound is vaporized or changed into a gas, and the atoms of uranium of different weights are separated. The highly fissionable uranium is used for weapons and as fuel elements for various reactors.
Used fuel elements may be processed to recover any unfissioned uranium. The unfissioned uranium can then be returned to the reactor.
Uranium is very reactive. It combines vigorously with oxygen and is pyrophoric. This means that small chips of the metal may burn spontaneously in air, as magnesium does.