On Monday August 6, 1945 the U.S. Bomber Enola Gay flew over the Japanese city of Hiroshima. Seconds later a metallic projectile fell towards its target. In a blinding flash the world felt the power of a new age, the nuclear age.
The study of radiation that would eventually lead to these uranium weapons began in 1798. It was in this year that the german chemist Martin Heinrich Klaproth identified the element uranium. Uranium was not isolated in a metallic state until 1841. The radioactive properties of uranium were first discovered in 1896 when a French physicist Antoine Henti Becquerel studied the properties of uranyl sulfate.
Although science found uranium in 1789, the study of uranium dates back much further. As early as the sixteenth century it was recognized that men who worked in pitchblende( a chemical containing iron ore) mines were subject to fatal pulmonary diseases. An early study of the Schneeberg mines of Germany conducted between 1869 and 1877 found that 650 miners working in the mines had a life expectancy of 20 years after entering the mines.
It was two german doctors, Harting and Hesse, who brought this to the public. The doctors found that 75 percent of the miner deaths were due to lung cancer. But with their scientific knowledge the doctors could only assume that the deaths were caused by the inhalation of arsenic. Later studies between 1900 and 1940 found that the deaths were caused by radiation in the mines.
The radiation the miners were exposed to would later be identified as uranium. Uranium is a natural occurring element, it has a atomic count of 92. Uranium is easily identified by its properties. Uranium melts at about 1132C, boils at about 3818C, and has a specific gravity of 19.05 at 25C. Uranium has three crystalline forms, of which the one that forms at about 770C is malleable and ductile. Uranium is soluble in hydrochloric acids and nitric acids, but not in alkalies.
Uranium never occurs naturally in the free state but is found as an oxide or complex salt in minerals such as pitchblende and carnotite. It has an average concentration in the earths crust of about 2 parts per million, and ranks 48th among the natural occurring elements on earth. Pure uranium consists of more than 99 percent of the isotope uranium-238, less than 1 percent of the isotope uranium-235, and a trace of uranium 234. Artificially produced isotopes of uranium-235, 237, and 239 have also been produced.
Since uranium is rare, a long and difficult process must be used to mine and process the uranium. First the uranium must be mined in a underground or surface uranium ore mine. Next the uranium must be milled. During this process chemicals are used to convert and purify the uranium ore into semirefined oxide( U3O8) known as yellow cake. The second stage in this conversion process is to change the U3O8 into UF6. The next step for the uranium is enrichment. In enrichment, the UF6( which is a gas at room temperature) is forced through about 1700 barriers in which the uranium concentration is increased from the natural 0.7 percent to a level of 3 to 4 percent. The final stage in the preparation of uranium is fuel fabrication. In this process UF6 is converted to uranium dioxide( UO2).
In 1938, the potential of refined uranium was found when Otto Hahn and Fritz Strassman bombarded a uranium metal with a stream of neutrons. At the conclusion of their experiment, they found a trace of barium in the uranium. Later they found that the release of energy and the presence of barium were caused by the splitting of uranium atoms. It was at that moment that the world was first introduced to man controlled nuclear power.
After the successful splitting of an atom, many nations set to work to find a way to produce and extract energy from the reaction. The first generation of electric power from nuclear power was achieved at a reactor testing center in Arco, Idaho. This early generating plant utilized a form of nuclear energy call fission. In this process uranium-235s nuclei is split open when struck by an sub-atomic particle called a neutron. This breaking open releases two or three neutrons which then split open still