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Revision as of 09:24, 17 April 2006 by ER MD (talk | contribs) (health section moved to back of article please re-add legality, i accidentally deleted it)(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff)Depleted uranium (DU) is uranium which contains mostly Uranium-238 and a reduced proportion of the isotope Uranium-235. It is a toxic byproduct of the enriching of natural uranium for use in nuclear reactors. DU is what is left over when most of the fissile radioactive isotopes of uranium are removed. The names Q-metal, depletalloy, and D-38, once applied to depleted uranium, have fallen into disuse.
As a radioactive byproduct otherwise requiring long term storage as low level nuclear waste, depleted uranium is an inexpensive but controlled material. It is useful for its extremely high density, which is only slightly less than that of tungsten. However, it has extremely poor corrosion properties, is pyrophoric (it will burn spontaneously when small particles are exposed to air), and since it, like all heavy metals, is toxic, as well as being radioactive, the facilities for processing it need to monitor and filter airborne particles.
Production and availability
Natural uranium metal contains about 0.71% U-235, 99.28% U-238, and about 0.0054% U-234. Depleted uranium contains only 0.2% to 0.4% U-235, the remainder having been removed and concentrated into enriched uranium through the process of isotope separation. The enrichment process does not create U-235 but merely separates the different isotopes of uranium. Therefore the process leaves large amounts of U-238 uranium as a byproduct. This byproduct is referred to as depleted uranium. For example producing 1 kg of 5% enriched uranium requires 11.8 kg of natural uranium, leaving about 10.8 kg of depleted uranium with 0.3% U-235.
The Nuclear Regulatory Commission (NRC) defines depleted uranium as uranium in which the percentage of the U isotope by weight is less than 0.711 percent (See 10 CFR 40.4.) The military specifications designate that the DU used by DoD contain less than 0.3 percent U (AEPI, 1995). In actuality, DoD uses only DU that contains approximately 0.2 percent U (AEPI, 1995).
- World Depleted Uranium Inventory
Nuclear energy applications
In a nuclear reactor, uranium-238 can be used to breed plutonium, which itself can be used in a nuclear weapon or as a reactor fuel source. In fact, in a typical nuclear reactor, up to a third of the generated power does come from the fission of Plutonium-239 (not supplied as a fuel to the reactor, but transmuted from Uranium-238).
Breeder reactors
Depleted uranium is not usable directly as nuclear fuel. Depleted uranium can be used as a source material for creating the element plutonium. Breeder reactors carry out such a process of transmutation to convert "fertile" isotopes such as U-238 into fissile plutonium. It has been estimated that there is anywhere from 10,000 to five billion years worth of Uranium-238 for use in these power plants . Breeder technology has been used in several reactors .
As of December 2005, the only breeder reactor producing power is BN-600 in Beloyarsk, Russia. The electricity output of BN-600 is 600 megawatts. Russia has planned to build another unit, BN-800, at Beloyarsk nuclear power plant. Also, Japan's Monju breeder reactor is planned for restart, having been shut down since 1995, and both China and India have announced intentions to build breeder reactors.
The Clean And Environmentally Safe Advanced Reactor (CAESAR), a nuclear reactor concept that would use steam as a moderator to control delayed neutrons, will potentially be able to burn DU fuel rods once the reactor is started with LEU. This design is still in the early stages of development.
Radiation shielding
DU is also used as a radiation shield — its alpha radiation is easily stopped by the non-radioactive casing of the shielding and the uranium's high atomic weight and high number of electrons is highly effective in absorbing gamma radiation and x-rays. However, DU is not as effective as ordinary water for stopping fast neutrons. Both metallic depleted uranium and depleted uranium dioxide are being used as materials for radiation shielding. Depleted uranium is about five times better as a gamma ray shield than lead, so a shield with the same effectivity can be packed into a thinner layer.
DUCRETE, a concrete made with uranium dioxide aggregate instead of gravel, is being investigated as a material for Dry cask storage systems to store radioactive waste.
Downblending
The opposite of enriching is downblending. Surplus highly enriched uranium can be downblended with depleted uranium to turn it into low enriched uranium and thus suitable for use in commercial nuclear fuel.
Depleted uranium is also used (with recycled plutonium) from weapons stockpiles for making mixed oxide fuel (MOX) which is now being redirected to become reactor fuel. This dilution, also called downblending, means that any nation or group that acquired the finished fuel would have to repeat the (very expensive and complex) enrichment and separation processes before assembling a weapon.
Military applications
Staballoys are metal alloys of a high proportion of depleted uranium with other metals, usually titanium or molybdenum, designed for use in kinetic energy penetrator armor-piercing munitions. They are about twice as dense as lead. One formulation has a composition of 99.25% by weight of depleted uranium and 0.75% by weight of titanium. Other variant can have 3.5% by weight of titanium.
Incendiary projectile munitions
Depleted uranium is very dense; at 19050 kg/m³, it is 70% denser than lead. Thus a given weight of it has a smaller diameter than an equivalent lead projectile, with less aerodynamic drag and deeper penetration due to a higher pressure at point of impact. DU projectile ordnance is often incendiary because of its pyrophoric property. DU munitions, in the form of ordnance, tank, and naval artillery rounds, are deployed by the armed forces of the United States, United Kingdom, Israel, France, China, Russia, Pakistan, and others. DU munitions are manufactured in 18 countries.
Most military use of depleted uranium has been as 30 mm and smaller ordnance, primarily the 30mm PGU-14/B armour-piercing incendiary round from AH-64 Apache helicopters and the GAU-8 Avenger cannon of the A-10 Thunderbolt II by the U.S. Army and Air Force. 25 mm DU rounds have been used in the M242 gun mounted on the U.S. Army's Bradley Fighting Vehicle and LAV-AT. The U.S. Marine Corps uses DU in the 25 mm PGU-20 round fired by the GAU-12 Equalizer cannon of the AV-8B Harrier, and also in the 20 mm M197 gun mounted on AH-1 helicopter gunships.
Another use of DU is in kinetic energy penetrators anti-armor role. Kinetic energy penetrator rounds consist of a long, relatively thin penetrator surrounded by discarding sabot. Two materials lend themselves to penetrator construction: tungsten and depleted uranium, the latter in designated alloys known as staballoys. The US Army uses DU in an alloy with around 3.5% titanium. Staballoys, along with lower raw material costs, have the advantage of being easy to melt and cast into shape; a difficult and expensive process for tungsten. Depleted uranium is favoured for the penetrator because it is self-sharpening and pyrophoric. On impact with a hard target, such as an armoured vehicle, the nose of the rod fractures in such a way that it remains sharp. The impact and subsequent release of heat energy causes it to disintegrate to dust and combust when it reaches air because of its pyrophoric properties (compare to ferrocerium). After a disintegrated DU penetrator reaches the interior of an armored vehicle, it explodes, often igniting ammunition and fuel, burning the crew, and causing the vehicle to explode. DU is used by the U.S. Army in 120 mm or 105 mm cannons employed on the M1 Abrams and M60A3 tanks. The Russian military has used DU munitions in tank main gun ammunition since the late 1970s, mostly for the 115 mm guns in the T-62 tank and the 125 mm guns in the T-64, T-72, T-80, and T-90 tanks.
The DU content in various munitions is 180 g in 20 mm projectiles, 200 g in 25 mm ones, 280g in 30 mm, 3.5 kg in 105 mm, and 4.5 kg in 120 mm penetrators. It is used in the form of Staballoy, alloyed with small proportion of other metals. The US Navy used DU in its 20 mm Phalanx CIWS guns, but switched in the late 1990s to armor-piercing tungsten for this application, because of the fire risk associated with stray pyrophoric rounds. DU was used during the mid-1990s in the U.S. to make 9mm and similar caliber armor piercing bullets, grenades, cluster bombs, and mines, but those applications have been discontinued, according to Alliant Techsystems. Whether or not other nations still make such use of DU is difficult to determine.
Incendiary uranium munitions may be implicated in some aspects of Gulf War syndrome and adverse reproductive outcomes such as congenital malformations. The United Nations Human Rights Commission passed a resolution to ban the use of depleted uranium in projectile weapons because they claimed it is not limited in time or space to the legal field of battle, or to military targets; it continues to act after the war; it is inhumane because it causes serious health issues, it causes harm to future civilian occupants and passers by (including unborn children and those breathing the air or drinking water); and it has an unduly negative and long term effect on the natural environment and food chain.
History
DU started to be stored in stockpiles in the 1940's when the U.S. and USSR began their nuclear weapons and nuclear power programs. While it is quite possible to design civilian power reactors with unenriched fuel, both nuclear weapons production and submarine reactors require the concentrated isotope. Originally it was conserved in hopes that more efficient enrichment techniques would allow further extraction of the fissile isotope; however those did not materialize. The Pentagon reported in the 1970s that the Soviet military had developed armor plating for Warsaw Pact tanks that NATO ammunition couldn't penetrate, and began searching for material to make harder bullets after testing various metals, ordnance researchers settled on depleted uranium.
What caused this particular material to be utilized as a form of ammunition was not only its unique physical properties and effectiveness in that role, but the fact that it was readily available, whereas tungsten, the only other candidate, had to be sourced from China. With DU stockpiles estimated to be in excess of 500,000 tons, the financial burdens associated with the housing of this kind of material quickly became apparent and that too made it more economical to use rather than store. Thus from the late 1970s onwards the US, the Soviet Union, Britain and France, began converting otherwise useless stockpiles of DU into Kinetic energy penetrators.
Photographic evidence of destroyed equipment suggests that DU was first used during the 1973 Arab-Israeli war. Various written reports cite information that was obtained as a consequence of that use.
The US and NATO Armed Forces argue that DU causes negligible increases in radioactivity and therefore minimum health risk; however, this neglects the non-radiological hazards of its toxicity. Mounting concerns have prompted calls for a ban on the use of this material, but thus far military analysts judge that its benefits outweigh its costs.
Nuclear weapons
Most modern nuclear weapons utilize depleted uranium as a "tamper" material (see Nuclear weapon design). A tamper which surrounds a fissile core works to reflect neutrons and add inertia to the compression of the plutonium charge. As such, it increases the efficiency of the weapon and reduces the amount of critical mass required.
In thermonuclear weapons using a Teller-Ulam design (by which the energy of a fission bomb is used to start a fusion reaction), a depleted uranium "tamper" is also used around the fusion fuel. In the process of detonation, the high flux of very energetic neutrons from the resulting fusion reaction causes the U-238 tamper to fission and adds energy to the yield of the weapon. Such weapons are referred to as fission-fusion-fission weapons after the three consecutive stages of the explosion. The larger portion of the total explosive yield in this design comes from the final fission stage fueled by DU, producing enormous amounts of radioactive fission products. For example, 77% of the 10.4 megaton yield of the Ivy Mike thermonuclear test in 1952 came from fast fission of the DU tamper. Because DU has no critical mass, it can be added to thermonuclear bombs in almost unlimited quantity. The 1961 Soviet test of Tsar Bomba produced "only" 50 megatons (still the largest man-made explosion in history), over 90% from fusion, because the DU final stage was replaced with lead. Had DU been used, the yield could have been as much as 100 megatons, and would have produced fallout equivalent to one third of the global total at that time.
Civilian applications
Civilian applications for depleted uranium are fairly limited and are typically unrelated to its radioactive properties. It primarily finds application as ballast because of its high density. 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. Other relatively minor consumer product uses have included: the manufacture of pigments and glazes; incorporation into dental porcelain used for false teeth to simulate the fluorescence of natural teeth; and in uranium-bearing reagents used in chemistry laboratories.
U.S. Nuclear Regulatory Commission regulations at 10 CFR 40.25 establish mandatory licensing for the use of depleted uranium contained in industrial products or devices for mass-volume applications. Other jurisdictions have similar regulations.
Aircraft
Aircraft may also contain depleted uranium trim weights (a Boeing 747 may contain 400 to 1,500 kg). However there is some controversy about its use in this application because of concern about the uranium entering the environment should the aircraft crash, since the metal can oxidise to a fine powder in a fire. However the other hazardous material releases from a burning commercial aircraft overshadow the contributions made by DU. Nevertheless, its use has been phased out in many newer aircraft, for example both Boeing and McDonnell-Douglas discontinued using DU counterweights in the 1980s.
Forklifts
It has been stated by forklift industry leaders that the mere substitution of depleted uranium metal for iron counterweights would revolutionize the industry by ushering in design concepts not previously available. Notably reduction in overall length when applied to the crucial right-angle stacking (the amount of space required to execute a 90° turn) dimension of the forklift, results in a 10% increase in usable warehouse floor space.
Catalysts
Uranium oxides are known to have high efficiency and long-term stability when used to destroy volatile organic compounds (VOCs) when compared with some of the commercial catalysts, such as precious metals, TiO2, and Co3O4 catalysts. Much research is being done in this area, DU being favoured for the uranium component due to its low radioactivity. (Hutchings, G. J., et. al., AUranium-Oxide-Based Catalysts for the Destruction of Volatile Chloro-Organic compounds,@ Nature, 384, pp. 341B343, 1996.)
Semiconductors
Main article: Uranium dioxideSome uranium oxides, namely uranium dioxide, have semiconductor properties similar to other semiconductor materials. Its band gap lies at around 1.3 eV. Its Seebeck coefficient is very high, making it a promising material for thermoelectric applications. It is also capable of withstanding high temperatures.
The low level of alpha radiation produced in the material is a cause of electronic noise, causing multiple single-event upsets. Schottky diodes made of uranium oxide and a p-n-p transistor of uranium dioxide were successfully demonstrated in a laboratory.
Pigments
Uranium was widely used as a coloring matter for porcelain and glass in the 19th century. The total production of uranium pigments was about 260 tonnes (with an uranium contents of ~70%), 150 tonnes of which were used for uranium glass. The practice was believed to be a matter of history, however in 1999 concentrations of 10% depleted uranium were found in "jaune no.17" a yellow enamel powder that was being produced in France by Cristallerie de Saint-Paul, a manufacturer of enamel pigments. The depleted uranium used in the powder was sold by Cogéma's Pierrelatte facility. Cogema has since confirmed that it has made a decision to stop the sale of depleted uranium to producers of enamel and glass.
Health concerns
Soluble uranium salts are toxic, causing kidney damage in large doses and proven reproductive, neurological, and immunological harm in mammals. Soluble uranium salts are excreted in the urine, although some accumulation in lungs, bones, and soft tissues does occur. (Many uranium compounds are partially soluble, and some are insoluble.) The World Health Organisation has established a daily "tolerated intake" of soluble uranium salts for the general public of 0.5 μg/kg body weight (or 35 μg for a 70 kg adult): exposure at this level is not thought to lead to any significant kidney damage.
Safety and environmental issues
About 95% of the depleted uranium produced to date is being stored as uranium hexafluoride, (D)UF6, within steel cylinders in open air yards adjacent to enrichment plants. Each cylinder contains up to 12.7 tonnes (or 14 tons) of UF6. In the U.S. alone, 560,000 metric tons of depleted UF6 had accumulated by 1993. As of 2005, 686,500 metric tons in 57,122 storage cylinders were located near Portsmouth, Ohio, Oak Ridge, Tennessee, and Paducah, Kentucky. , The long-term storage of DUF6 presents environmental, health, and safety hazards due to its chemical instability. When UF6 is exposed to moist air, it reacts with the water in the air to produce UO2F2 (uranyl fluoride) and HF (hydrogen fluoride) both of which are highly soluble and toxic. Storage cylinders must be regularly inspected for evidence of corrosion and leakage. The estimated life time of the steel cylinders is measured in decades.
External links
Scientific bodies
- Canadian Uranium Medical Research Centre
- German World Uranium Weapons Conference
- U.K. Depleted Uranium Oversight Board
United Nations
- "Depleted Uranium: Sources, Exposure and Health Effects," World Health Organization, Ionizing Radiation Unit, 2001 (see Chapter 8, "The Chemical Toxicity of Uranium," in particular.)
- Sub-Commission resolution 1996/16
(resolves and states DU to be "incompatible" with human rights and international law; lists DU as "particularly" one "weapon of mass destruction or indiscriminate effect") - UN High Commission for Human Rights, 1998
(statement that DU is prohibited and contravenes prior UN resolutions) - "Human rights and weapons of mass destruction, or with indiscriminate effect, or of a nature to cause superfluous injury or unnecessary suffering"
(The UN 2002 report)
Scientific reports
- U.S. Center for Disease Control's Toxicological Profile for Uranium (includes discussion of teratogenic and immunotoxic effects)
- Salbu, B. et al. (2005) "Oxidation states of uranium in depleted uranium particles from Kuwait," Journal of Environmental Radioactivity, 78, 125–135. Abstract: "Environmental or health impact assessments for ... DU munitions should ... take into account the presence of respiratory UO3...."
- Wilson, W.B. (1961) "High-Pressure High-Temperature Investigation of the Uranium-Oxygen System," Journal Of Inorganic and Nuclear Chemistry, 19, 212-222, p. 213.
- Arfsten, D.P. et al. (2001) "A review of the effects of uranium and depleted uranium exposure on reproduction and fetal development," Toxicology and Industrial Health, vol. 17, pp. 180-91. Summary contains: "A number of studies have shown that natural uranium is a reproductive toxicant...."
- Hindin, R. et al. (2005) "Teratogenicity of depleted uranium aerosols: A review from an epidemiological perspective," Environmental Health, vol. 4, pp. 17. "Conclusion: In aggregate the human epidemiological evidence is consistent with increased risk of birth defects in offspring of persons exposed to DU."
- Domingo, J.L. (2001) "Reproductive and developmental toxicity of natural and depleted uranium: a review" Reproductive Toxicology, 15, 603-609.
- Durakovic A. (1999) "Medical effects of internal contamination with uranium," Croatian Medical Journal, vol. 40, pp. 49-66. Abstract: "well documented evidence of reproductive and developmental toxicity...."
- Briner, W. and J. Murray (2005) "Effects of short-term and long-term depleted uranium exposure on open-field behavior and brain lipid oxidation in rats," Neurotoxicology and Teratology, vol. 27, pp. 135-44. Abstract: "DU is a toxin that crosses the blood-brain barrier, producing behavioral changes in male rats and lipid oxidation regardless of gender in as little as 2 weeks...."
- Monleau, M. et al. (2005) "Bioaccumulation and behavioural effects of depleted uranium in rats exposed to repeated inhalations," Neuroscience Letters, vol. 390, pp. 31-6. Abstract: "depleted uranium is able to enter the brain after exposure to repeated inhalation, producing behavioral changes."
- Lestaevel, P. et al. (2005) "The brain is a target organ after acute exposure to depleted uranium" Toxicology, 212, 219-226.
- Busby, C. and S. Morgan (2006) "Did the use of Uranium weapons in Gulf War 2 result in contamination of Europe?" European Biology and Bioelectromagnetics, 1(5), 650-668.
- Depleted Uranium article from the Royal Society (does not include discussion of teratogenic and immunotoxic effects)
- An Analysis of Uranium Dispersal and Health Effects Using a Gulf War Case Study by Sandia National Laboratories (does not include discussion of teratogenic and immunotoxic effects)
- Depleted Uranium Human Health Fact Sheet by Argonne National Laboratory Environmental Assessment Division (does not include discussion of nonradiological teratogenic, developmental toxicity, and immunotoxic effects)
- Uranium Human Health Fact Sheet (does not include discussion of teratogenic and immunotoxic effects)
Other publications
- "After the Dust Settles" (Bulletin of the Atomic Scientists report from 1999)
- Better World Links on Depleted Uranium Weapons 500+ links
- 'Blowin' in the Wind' information about a film about depleted uranium by David Bradbury
- Campaign Against Depleted Uranium
- Depleted UF6 Management Information Network – on U.S. Department of Energy's inventory of depleted uranium hexafluoride.
- Guardian Unlimited's Special Report on Depleted Uranium
- International Atomic Energy Agency Depleted Uranium FAQ
- International Coalition to Ban Uranium Weapons
- My Life Living With Depleted Uranium
- Proposal for Research on Depleted Uranium (U.K. Ministry of Defence)
- Radioactive Wounds of War
- U.S. Soldiers Contaminated With Depleted Uranium Speak Out – Democracy Now!, April 5, 2004
- Uranium and Weapons – Uranium Medical Research Centre
- Annotated bibliography for depleted uranium from the Alsos Digital Library
- Nuclear Files.org information and articles relating to depleted uranium
- Have DU Will Travel series of sixteen articles in the Crawford, Texas Lone Star Iconoclast
- DU-Watch
- International Atomic Energy Agency Depleted uranium FAQ
- The Depleted UF6 Management Information Network
- Cost-Effectiveness of Utilizing Surplus Depleted Uranium (DU)
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