For example, nearly one third of all mill tailings from abandoned mill operations are on lands of the Navajo nation alone. Others continue to suffer the effects of land and water contamination due to seepage and spills from tailings piles.
Uranium is generally used in reactors in the form of uranium dioxide UO 2 or uranium metal; nuclear weapons use the metallic form. Production of uranium dioxide or metal requires chemical processing of yellowcake. Further, most civilian and many military reactors require uranium that has a higher proportion of uranium than present in natural uranium. The process used to increase the amount of uranium relative to uranium is known as uranium enrichment. Some research reactors and all U.
To enrich uranium, it must first be put in the chemical form uranium hexafluoride UF 6. After enrichment, UF6 is chemically converted to uranium dioxide or metal. A major hazard in both the uranium conversion and uranium enrichment processes comes from the handling of uranium hexafluoride, which is chemically toxic as well as radioactive.
Moreover, it reacts readily with moisture, releasing highly toxic hydrofluoric acid. Conversion and enrichment facilities have had a number of accidents involving uranium hexafluoride.
The bulk of waste from the enrichment process is depleted uranium—so-called because most of the uranium has been extracted from it. Depleted uranium has been used by the U.
It was incorporated into these conventional weapons without informing armed forces personnel that depleted uranium is a radioactive material and without procedures for measuring doses to operating personnel. The enrichment process can also be reversed. Uranium metal at various enrichments must be chemically processed so that it can be blended into a homogeneous material at one enrichment level. In , French physicist Henri Becquerel left some uranium salts on a photographic plate as part of some research on how light influenced these salts.
To his surprise, the plate fogged up, indicating some sort of emissions from the uranium salts. Martin Heinrich Klaproth, a German chemist, discovered uranium in , although it had been known about since at least A. Klaproth discovered the element in the mineral pitchblende, which at the time was thought to be a zinc and iron ore. The mineral was dissolved in nitric acid, and then potash potassium salts was added to the remaining yellow precipitate.
Klaproth concluded that he had discovered a new element when the reaction between the potash and precipitate didn't follow any reactions of known elements. His discovery turned out to be uranium oxide and not pure uranium as he had originally believed. According to the Los Alamos National Laboratory , Klaproth named the new element after the recently discovered planet Uranus, which was named for the Greek god of the sky.
Uranium was found to be radioactive in by Antoine H. Becquerel, a French physicist. Becquerel had left a sample of uranium on top of an unexposed photographic plate, which became cloudy. He concluded it was giving off invisible rays, according to the Royal Society of Chemistry. This was the first instance that radioactivity had been studied and opened up a new field of science. Marie Curie, a Polish scientist, coined the term radioactivity shortly after Becquerel's discovery, and with Pierre Curie, a French scientist, continued the research to discover other radioactive elements, such as polonium and radium, and their properties.
The universe's uranium formed 6. It is all over the planet, and makes up about 2 to 4 parts per million of most rocks. It is 48th among the most abundant elements found in natural crustal rock, according to the U. Department of Energy , and is 40 times more abundant than silver. Though uranium is highly associated with radioactivity, its rate of decay is so low that this element is actually not one of the more radioactive ones out there.
Uranium has a half-life of an incredible 4. Western Canada is particularly rich in uranium, with anywhere between 28 to kilograms of uranium per tonne as opposed to the usual 3 grams per tonne found elsewhere.
This high abundance, taken in conjunction with the difficult geological conditions and the harsh climate have made the extraction process an almost entirely automated one.
Yellow cake The radioactivity of uranium is low, and so no particularly high standards of radioprotection are needed: as can be seen with the above workmen. This high concentration makes it much easier to transport the uranium from the mine to the factory.
Weapon-grade and civilian uranium Natural uranium is poor in the fissile isotope, containing as it does only 0. U and U which has neutrons are the most common isotopes of uranium. Uranium naturally contains all three isotopes U, U and U , and it rarely varies more than 0. To produce fuel-grade uranium, the uranium has to be processed to produce uranium dioxide and to enrich or concentrate the U in the fuel pellets. During this processing, depleted uranium DU , enriched in U and depleted in U, is produced.
DU and enriched uranium have numerous civilian and military uses. Since U is the most radioactive isotope of uranium, the removal of it to makes DU the least radioactive phase of uranium, but it still has heavy metal toxicity issues.
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