Depleted uranium

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Depleted uranium (DU) is uranium which contains a reduced proportion of the fissile isotope U-235 and (usually) the highly radioactive but rare isotope U-234, compared to natural uranium.

Related Topics:
Uranium - Fissile - Isotope - U-235 - Radioactive

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Natural uranium contains nominally 0.7110% U-235 (+/- 0.1% variation) and 99.28305% U-238 (and 0.0054% U-234), while depleted uranium contains only 0.2 to 0.4 weight-percent U-235.

Related Topics:
Natural uranium - U-238

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The U-235 is concentrated into enriched uranium through the process of isotope separation for use in nuclear reactors and nuclear weapons:

Related Topics:
Enriched uranium - Isotope separation - Nuclear reactor - Nuclear weapon

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• Nuclear weapons usually use uranium containing 90% or more of U-235 (a lower grade is possible but makes the weapon less efficient).
• Commercial light water nuclear reactor fuel is usually enriched up to a maximum of 5% (the 5% limit is set by the currently licensed transport containers — in the future the 5% limit may be increased up to 7% for improved fuel economy).
• Research reactor fuel is today limited to maximum 20% (most older research reactors have been or will be converted down to this lower enrichment level).

The enrichment process does not create U-235; rather, the isotopes of uranium are merely separated. Therefore the process leaves large amounts of depleted uranium as a waste product. For example producing 1kg of 5% enriched uranium requires 11.8kg of natural uranium, leaving about 10.8 kg of depleted uranium with 0.3% U-235.

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The United States Department of Energy currently has an inventory of 704,000 tonnes of depleted uranium hexafluoride (stored in 58,000 metal cylinders), corresponding to 476,000 tonnes of uranium http://web.ead.anl.gov/uranium/. It encourages the use of DU as a means of disposing of the stock, and plans to eventually convert the remaining inventory to a less toxic form, probably either uranium metal or oxide.

Related Topics:
United States Department of Energy - Uranium hexafluoride

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As a product otherwise requiring long term storage as low level radioactive waste, depleted uranium can be obtained cheaply. It is useful for its extremely high density, which is only slightly less than that of tungsten. As well as a lower initial cost, depleted uranium is easier to roll, machine and cast than tungsten. However, it has extremely poor corrosion properties (tending to spall on exposure to air) and since it is toxic and radioactive the facilities for processing it need to monitor and filter dust and airborne particles. One disadvantage of DU is that it needs to be correctly handled when an object containing it is scrapped. The uranium is normally leased from the manufacturer and subsequently returned at the end of the object's life.

Related Topics:
Tungsten - Corrosion - Spall - Toxic

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Depleted uranium: Nuclear applications ►