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Depleted uranium

Depleted uranium (DU) is uranium which has had most of the fissile isotope U-235 removed, and consists of mostly U-238. The U-235 is concentrated into enriched uranium through the process of isotope separation for use in nuclear reactors and nuclear weapons. The remaining, less radioactive (40% as radioactive as natural uranium), U-238 is waste material from this enrichment process. During the Manhattan Project depleted uranium had the codename tubealloy, a term that is still occasionally used. Uranium is mined mainly for its U-235 content, so the excess U-238 can be obtained cheaply and is used for its extremely high density, only slightly less than that of tungsten.

A major use of DU is as the head of a kinetic projectile fired to penetrate armour, so it is used by tanks and other military platforms. Depleted uranium is very dense: at 19.05 g/cmł it is 70% denser than lead, allowing it to penetrate most conventional armor. A DU projectile burns and melts as it penetrates steel, becoming 'sharper' rather than blunting. As the projectile passes through armor, the heat build-up causes it to catch fire and disintegrate into fine particles on re-encountering air.

The US military is a major user of DU projectiles. It uses the DU in an alloy with around 3.5% titanium. It is used by the US Army in 120 mm or 105 mm caliber by the M1 Abrams tanks and in 25 mm by the M919 mounted on the M2 Bradley and the LAV-AT. The US Navy use it in their 25 mm CIWS and the Mk 38 machine gun. The Air Force uses it in 30 mm caliber on the A-10 Thunderbolt II and the Marine Corps in 25 mm on their AV-8B Harrier.

Some modern tanks, including the Abrams, "fight fire with fire" by using depleted uranium as one of the layers of their complex, multi-layered armor systems.

Depleted uranium is also used in sailboat keels, as counterweights in oil drills, and in other places where there is a need to place a weight that occupies as little space as possible, such as in aircraft ballast.

Health concerns

Environmental groups have raised concerns about the use of this material. Whilst its radioactivity per se isn't of concern, uranium is also chemically toxic, roughly as much as lead. The chemical toxicity is of concern to the occupants of the vehicle hit and it may be a major problem for troops or civilians who come close later. The health effects of depleted uranium have been postulated to be one of the possible causes of Gulf war syndrome. This possibility has been widely denied by authorities and studies in countries that use DU weapons.

Recent studies of scientific bodies outside the USA and the UK - which are strong DU ammunition proponents - indicated several things:

Toxic material from shot DU ammunition does disperse into the air much more easily and widely than expected (since uranium is one of the heaviest metals there are, this came rather unexpectedly). Also DU disperses into the water, as mentioned in the UNEP study [4]:

"The most important concern is the potential for future groundwater contamination by corroding penetrators (ammunition tips made out of DU). The penetrators recovered by the UNEP team had decreased in mass by 10-15% due to corrosion. This rapid corrosion speed underlines the importance of monitoring the water quality at the DU sites on an annual basis."

While DU studies from the military sector mostly were conducted under the assumption about external exposure to DU materials, newer studies took inhalation of particles from the remains of used ammunition into consideration. These studies indicate that the battlefield use of DU ammunition may have grave consequences, especially if used near population centers.
Small amounts of radiation may even be more harmful to the body than bigger doses may be [1,2,3]. Damaged cells resulting from lower doses of radiation seem to be less efficiently repaired by the body. This seems to be a possible source of cancer. This may lead to controversy in the future if the facts become more clear (proven by more studies) and more commonly known, since this may be important to people living in the vicinity of nuclear power plants as well.

These facts together may indicate, that DU ammunition is actually quite of a health problem, and endangers the civilian population if left on the battlefield.

Bibliography, external links and references

"Evidence for a lack of DNA double-strand break repair in human cells exposed to very low x-ray doses" (http://www.pnas.org/cgi/content/abstract/0830918100v1?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&author1=Lobrich&searchid=1050501068156_3074&stored_search=&FIRSTINDEX=0) at PNAS Online (http://www.pnas.org)
"Clustered DNA damages induced in isolated DNA and in human cells by low doses of ionizing radiation" (http://www.pnas.org/cgi/content/full/97/1/103?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&titleabstract=DNA+radiation&searchid=1054053114644_5748&stored_search=&FIRSTINDEX=0), Vol. 97, Issue 1, 103-108, January 4, 2000, at PNAS Online (http://www.pnas.org)
"Mutagenesis and repair by low doses of radiation in mammalian cells" (http://www.pnas.org/cgi/content/full/99/19/12220) published on August 27, 2002 at PNAS Online (http://www.pnas.org)
Post Conflict Assessment Iraq (http://postconflict.unep.ch/publications/Iraq_DS_LowRes.pdf) by the United Nations Environment Programme
Depleted Uranium (http://www.royalsoc.ac.uk/du/intro.htm) article from the The Royal Society (http://www.royalsoc.ac.uk)
Report about the DU conference (http://www.uni-kassel.de/fb10/frieden/themen/DU-Geschosse/queck.html) in Prague at 24.-25.11.01 (in German)

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