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Uranium

Uranium was first identified as an element in 1789 by Martin Klaproth, a German chemist. The element was named after the planet Uranus. It is generally not found in concentrated deposits, although it is more abundant than silver, cadmium or mercury.

It remained little more than a curiosity for over a century, however, being used to manufacture vivid green glass but having little other application. Indeed uranium was treated as a waste product from pitchblende mining operations such as those established by Gilbert Labine at Great Bear Lake in northern Canada during the 1930s. Pitchblende was mined for its radium content, an element of interest to early researchers in radioactivity.

Uranium occurs in nature in two main isotopic forms: U-235 and U-238. Uranium 235 was the first element in which nuclear fission was observed. An atom of U-235 will capture a neutron and become U-236. U-236 is not stable and achieves stability by splitting into two lighter atoms, releasing some energy and two or three fast-moving neutrons. If those neutrons are slowed down sufficiently they can be captured by another atom of U-235 and the process is repeated. A piece of apparatus containing uranium-235, some material for slowing neutrons down, and some means to remove the heat energy produced is called a nuclear reactor.

Uranium can also be used in weapons, where a large amount of fission happens very quickly, releasing a large amount of energy. It is very difficult to achieve this explosive release of energy because the uranium has to be held in a concentrated position for the reaction to occur, but the explosion works to disperse the uranium and therefore stop the reaction. An electricity-producing reactor cannot explode like a bomb.

Uranium from Great Bear Lake was used by National Research Council Canada scientist George Lawrence in the construction of a prototype nuclear reactor that he built in the early 1940s in his lab at 100 Sussex Drive in downtown Ottawa. That prototype did not achieve sustained operation or it would have been the first operating nuclear reactor in the world. That achievement went to Enrico Fermi and his team, working at the University of Chicago in December 1942.

Today energy from the fission of uranium produces one sixth of the world's electricity. Because 20 kg of uranium produces as much energy as 400,000 kg of coal, nuclear power stations produce a lot less waste than fossil fuel stations. That means it is possible to store 100% of the waste and not pollute the environment.