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Uranium is a naturally occurring element, found in low levels in all rock, soil and water. It is the highest numbered element that occurs naturally in quantity and is always found in combination with other elements. The natural, as distinct from man made, importance of uranium is as the source of the heat that keeps the outer core of the earth liquid and drives mantle convection and hence plate tectonics.
The average concentration of uranium in soil ranges from 1 to 11 parts per million and in rock from 2 to 4 parts per million. As a reference point, the concentration of silver in rock is just 0.05 to 0.1 parts per million.
One of the earliest identified uses of uranium comes from a 1st century Roman villa in the Bay of Naples, Italy. Drinking glasses found there used uranium oxide as a yellow colorant. A thousand years later, this use as a colorant in glassmaking was evident in the Czech Republic, where pitchblende (also known as uraninite) was a by-product of silver mining at the Hapsburg's mines. Indeed, as late as the early 19th century, the world's only recorded source of uranium was from these mines.
The discovery of uranium as an element is attributed to Martin Heinrich Klaproth, in Berlin in 1789. He named the new element uranium after the planet Uranus, which had been discovered a few years earlier.
During the 19th century, uranium was generally regarded as a safe element and its main use continued as a colorant in glassmaking and ceramics. However, this was also a century of major scientific discoveries and some of those concerned uranium and lead directly to its current significance in medicine, power generation and military use. In 1841, Eugene-Melchior Peligot, a professor at the Central School of Arts and Manufactures in Paris, heated uranium tetrachloride and potassium and thus produced the first recorded uranium metal. Then, in 1895, Wilhelm Roentgen, while experimenting with X rays and energy sources, recorded the skeletal hand of his wife on a photographic plate when she accidentally moved her hand into the beam of the electron rays. Another accidental discovery occurred a year later, when Antoine Becquerel exposed a photographic plate to uranium crystals and found that the weak radioactivity in the crystals exposed the photographic plates. Pierre and Marie Curie were working with Becquerel and their work on the electrical conductivity of pitchblende led to the discovery of polonium and radium. Marie Curie later established that radiation was an atomic property and not an independent release.
Ernest Rutherford, Joseph John Thompson, Albert Einstein and Niels Bohr were all party to discoveries and developments in scientific understanding that lead to the theory of splitting the atom and the knowledge that energy was intensely concentrated within the atom's nucleus. Research published in 1939 by Otto Hahn and Fritz Strassman showed that the absorption of a neutron by a uranium nucleus sometimes caused the nucleus to split with the release of enormous amounts of energy. This splitting or breaking apart was referred to a nuclear fission and collaboration by Leo Szilard and Enrico Fermi at the University of Chicago created the first self-sustaining nuclear chain reaction inside the world's first nuclear reactor.
The timing of these developments was unfortunate as World War II was raging and the release of such enormous power through nuclear fission was seized on for military use. This culminated in the dropping of the uranium based atomic bomb over Hiroshima in 1945.
Happily, the civic uses of nuclear power received attention after World War II and in 1952 the town of Arco, Idaho, became the first in the world to have all of its electricity supplied by nuclear power. Then in 1956 the first commercial scale nuclear power plant was commissioned in Calder Hall, England. In 2007, the IAEA reported that 435 nuclear power plants were operating in 31 different countries. These are producing 16% of global electricity requirements.
USEFUL LINKS
The following are interesting Internet sites providing broader information on the uranium market and further background and history of uranium.
- World Nuclear Association:
- Australian Uranium Association:
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