Depleted uranium Guide, Meaning , Facts, Information and Description
Depleted uranium (DU) is uranium which has had most of the fissile isotope U-235 and the highly radioactive but rare isotope U-234 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 U-238 is 60% as radioactive as natural uranium. It is waste material from this enrichment process. During the Manhattan Project depleted uranium had the codename tuballoy, 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.
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2 Civilian applications 3 Health concerns 4 External links |
Military applications
A major use of DU is for high-energy penetrators for the anti-tank role. Depleted uranium is very dense: at 19.05 g/cm³, it is 70% denser than lead, allowing it to penetrate most conventional armor. Additionally, DU is pyrophoric: if it penetrates steel or other metal armor, the heat build-up causes it to disintegrate and combust when it reaches air. Against an armoured vehicle this is devastating, piercing the hull to create a white-hot ball of flame in the interior, killing the crew and igniting fuel and ammunition. 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, causing it to emerge from the other side of the armor accompanied by a white-hot ball of fire and a shower of molten shrapnel.
Not only is DU effective in the anti-armor role, depleted uranium armor-piercing penetrators are far less expensive to manufacture than those made of tungsten or other dense, non-radioactive materials. Depleted uranium is far easier to cast, whereas the hardness and high melting points of materials like tungsten makes manufacturing difficult.
Currently the US military is the primary user of DU in combat, though DU armor-piercing munitions were invented by the Soviets in the late 1970s and are still mass-produced in Russia today (as well as 17 other countries, including Pakistan). The US Army 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 and M60A3 tanks and in 25 mm by the M242 mounted on the M2 Bradley and the LAV-AT; some late-production M1A1HA and M1A2 Abrams tanks built after 1998 have DU rods as reinforcements as part of its armour plating in the front of the hull and the front of the turret. The US Navy uses it in its 20 mm Phalanx CIWS guns (though it has switched to tungsten for this application) and the 25 mm Mk38 machine gun. The Air Force uses the 30 mm PGU-14/B API round in the GAU-8 Avenger cannon of the A-10 Thunderbolt II and the Marine Corps in the 25 mm PGU-20 fired by the GAU-12 Equalizer cannon of the AV-8B Harrier and also in the 20 mm M197 mounted on AH-1 helicopter gunships.
The Russian military mainly uses DU munitions in tank main gun ammunition, mostly for the 115 mm guns in the T62 tank and the 125 mm guns in the T64, T72, T80, and T90 tanks. DU munitions (in the form of tank and naval artillery rounds) are also deployed by the armed forces of the UK, Israel, France, Japan, China, Russia, Pakistan, and many other countries.
Such applications include sailboat keels, as counterweights and sinker bars in oil drills, gyroscope rotors, and in other places where there is a need to place a weight that occupies as little space as possible. Tungsten could be used instead, but it is much more expensive (and although more expensive to work, this is offset by the pyrophoric and toxic nature of uranium). One disadvantage of DU is that it needs to be correctly handled when the object containing it is scrapped.
Aircraft may also contain depleted uranium counterweights (a Boeing 747 may contain 400–1,500 kg). However there is additional controversy about its use in this application because of concern about the uranium entering the environment should the aircraft crash, particularly as the metal is pyrophoric. This was highlighted by the collision of two Boeing 747s at Tenerife Airport in 1977 when the resulting fire consumed 3000 kg of the material. Consequently its use has been phased out in newer aircraft, for example both Boeing and McDonnell-Douglas discontinued using DU counterweights in the 1980s. However many aircraft remain in service using them and they are still available as second-hand spares.
An unexpected application is in Formula 1 racing cars. The rules state a minimum weight of 600 kg but builders strive to get the weight as low as possible and then bring it up to the 600 kg mark by placing depleted uranium under the front axle to achieve a better balance.
DU is also used as radiation shielded — its alpha radiation is easily stopped by the non-radioactive casing of the shielding and the uranium's high atomic weight is effective in absorbing gamma radiation.
Such issues are of concern to those fired upon by DU weapons, to those firing DU weapons, to those protected by DU armour-plating, and to civilians and troops operating in a theatre where DU is used.
The health effects of depleted uranium have been postulated to be one of the possible causes of Gulf war syndrome. Government officials have disputed this claim.
Studies of scientific bodies have resulted in mixed conclusions. Studies showing detrimental health effects have claimed the following:
Civilian applications
Depleted uranium is also used in a number of civilian applications, generally where a high density weight is needed.Health concerns
Environmental groups have raised concerns about the use of this material, particularly in munitions; arguing that not only is it dangerously radioactive, but it is also as toxic as lead.
"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 mainly evaluated 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. [1] [1] [1] In this model, cell damage resulting from lower doses of radiation is less efficiently repaired by the body, possibly leading to cancer. If this is proven out, it would be important to people living in the vicinity of nuclear power plants as well. However, some studies suggest that very small doses of radiation can actually decrease the likelihood of cancer, in an effect called hormesis.
- While DU is minimally radioactive (and its radioactivity figures are often cited by advocates of its use) its decay product - 234 Th - and its own daughter 234 Pa - are beta particle emitters with half-lives of several weeks (234 Pa decays to 234 U, with a half-life of hundreds of millennia; this isotope does not build to equilibrium concentration for a significant amount of time). When the two first isotopes in the decay chain reach their (tiny) equilibrium concentrations (over the months following manufacture), a DU fragment will emit 3 times the radiation due to DU itself, and most of this will be beta radiation - which can penetrate the skin or cause damage if ingested or inhaled.
The Vienna-based International Atomic Energy Agency reports, "based on credible scientific evidence, there is no proven link between DU exposure and increases in human cancers or other significant health or environmental impacts." [1] The US military watchdog group Federation of American Scientists has come to similar conclusions.
External links
Depleted uranium: Dirty bombs, dirty missiles, dirty bullets - San Francisco Bay View article by Leuren Moret
- Metal of Dishonor - documentary film by Peoples Video Network.
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