Depleted uranium

Depleted uranium (DU) is uranium which has a reduced proportion of the isotope Uranium-235. It is mostly made up of Uranium-238. The names Q-metal, depletalloy, and D-38, once applied to depleted uranium, have fallen into disuse.

Sources

Depleted uranium is a byproduct of the enriching of natural uranium for use in nuclear reactors. When most of the fissile radioactive isotopes of uranium are removed from natural uranium, the residue is called depleted uranium. A less common source of the material is reprocessed spent reactor fuel. The origin can be distinguished by the content of uranium-236,[1] produced by neutron capture from uranium-235 in nuclear reactors.

As a toxic and radioactive waste product that requires long term storage as low level nuclear waste, depleted uranium is costly to keep but relatively inexpensive to obtain. Generally the only real costs are those associated with conversion of UF₆ to metal. Its extremely high density, only slightly less than that of tungsten and its low cost make it attractive for a variety of uses. However, the material is prone to corrosion and small particles are pyrophoric. [2]

History

Depleted uranium was first 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, only about 10% of reactors ever built utilize that technology, and both nuclear weapons production and naval reactors require the concentrated isotope. Originally DU was conserved in the hope that more efficient enrichment techniques would allow further extraction of the fissile isotope; however those hopes did not materialize.

In the 1970s, The Pentagon reported that the Soviet military had developed armor plating for Warsaw Pact tanks that NATO ammunition couldn't penetrate. The Pentagon began searching for material to make harder bullets. After testing various metals, ordnance researchers settled on depleted uranium. DU was useful in ammunition not only because of its unique physical properties and effectiveness, but also because it was cheap and readily available. Tungsten, the only other candidate, had to be sourced from China. With DU stockpiles estimated to be more than 500,000 tons, the financial burden of housing this amount of low-level radioactive waste was very apparent. It was therefore more economical to use depleted uranium rather than storing it. Thus from the late 1970s, the U.S., the Soviet Union, Britain and France, began converting their stockpiles of depleted uranium 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.

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 rest of the U - 235 having been removed and concentrated into enriched uranium through the process of isotope separation. This process, which separates the different isotopes of uranium, leaves large amounts of U-238 uranium. It is this residue that is called depleted uranium. Producing 1 kg of 5% enriched uranium requires 11.8 kg of natural uranium, and leaves about 10.8 kg of depleted uranium with only 0.3% U-235 remaining.

• Depleted Uranium Fraction Calculator designed by: The WISE Uranium Project

The Nuclear Regulatory Commission (NRC) defines depleted uranium as uranium with a percentage of the ²³⁵U isotope that is less than 0.711 percent by weight (See 10 CFR 40.4.) The military specifications designate that the DU used by DoD contain less than 0.3 percent ²³⁵U (AEPI, 1995). In actuality, DoD uses only DU that contains approximately 0.2 percent ²³⁵U (AEPI, 1995).

World Depleted Uranium Inventory

Country	Organization	DU Stocks (in tons)	Reported
USA	DOE	480,000	2002
Russia	FAEA	460,000	1996
France	COGEMA	190,000	2001
UK	BNFL	30,000	2001
Germany	URENCO	16,000	1999
Japan	JNFL	10,000	2001
China	CNNC	2,000	2000
South Korea	KAERI	200	2002
South Africa	NECSA	73	2001
TOTAL		1,188,273	2002

Source: WISE Uranium Project

Military applications

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 several countries.

It had been widely assumed that the type used by the US in its weapons was the uncontaminated variety, until 2001 when UN scientists found evidence of contaminated DU in the field. The U.S. Army admitted the problem the following day, and began to correct the issue. [3] [4] [5] [6]

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 the GAU-8 Avenger cannon of the A-10 Thunderbolt II [7] by the 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. The US Navy's Phalanx CIWS's M61 Vulcan gatling gun used 20mm armor piercing penetrator rounds with discarding plastic sabots which were made using depleted uranium, later changed to tungsten.

DU penetrator from the PGU-14/B incendiary 30mm round

Armor plate

Because of its high density, depleted uranium can also be used in tank armor, sandwiched between sheets of steel armor plate. For instance, some late-production M1A1HA and M1A2 Abrams tanks built after 1998 have DU reinforcement as part of its armor plating in the front of the hull and the front of the turret and there is a program to upgrade the rest.

Projectile munitions

Another use of depleted uranium 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. Staballoys are metal alloys of depleted uranium with a very small proportion of other metals, usually titanium or molybdenum. One formulation has a composition of 99.25% by weight of depleted uranium and 0.75% by weight of titanium. Another variant can have 3.5% by weight of titanium. Staballoys are about twice as dense as lead and are designed for use in kinetic energy penetrator armor-piercing munitions. 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 burn 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, incinerating 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. 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.

It is thought that between 17 and 20 states, approximately, have weapons incorporating depleted uranium in their arsenals. They include the USA, the UK, France, Russia, Greece, Turkey, Israel, Saudi Arabia, Bahrain, Egypt, Kuwait, Pakistan, Thailand, Iraq and Taiwan. DU munitions are manufactured in 18 countries. While only the US and the UK have acknowledged using DU weapons, its use by other states cannot be excluded.The International Legality of the Use of Depleted Uranium Weapons: A Precautionary Approach, Avril McDonald, Jann K. Kleffner and Brigit Toebes, eds. (TMC Asser Press Fall-2003).

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: incorporation into dental porcelain used for false teeth to simulate the fluorescence of natural teeth; and in uranium-bearing reagents used in chemistry laboratories.

Uranium was widely used as a coloring matter for porcelain and glass in the 19th century. 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. [8]

DU is also used for shielding for radiation sources used in medical and industrial radiography.

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

Trim weights in aircraft

Aircraft may also contain depleted uranium trim weights (a Boeing 747 may contain 400 to 1,500 kg). This application of DU is controversial. If an aircraft crashes there is concern that the uranium would enter the environment: the metal can oxidise to a fine powder in a fire. While arguably other hazardous materials released from a burning commercial aircraft overshadow the contributions made by DU, its use has been phased out in many newer aircraft, Both Boeing and McDonnell-Douglas discontinued using DU counterweights in the 1980s.

Uranium hexafluoride

About 95% of the depleted uranium produced till now is stored as uranium hexafluoride, (D)UF₆, in steel cylinders in open air yards close to enrichment plants. Each cylinder contains up to 12.7 tonnes (or 14 US tons) of UF₆. In the U.S. alone, 560,000 tonnes of depleted UF₆ had accumulated by 1993. In 2005, 686,500 tonnes in 57,122 storage cylinders were located near Portsmouth, Ohio, Oak Ridge, Tennessee, and Paducah, Kentucky. [9], [10] The long-term storage of DUF₆ presents environmental, health, and safety risks because of 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 signs of corrosion and leaks. The estimated life time of the steel cylinders is measured in decades. [11]

There have been several accidents involving uranium hexafluoride in the United States. [12] The U.S. government has been converting DUF₆ to solid uranium oxides for disposal. [13] Such disposal of the entire DUF₆ inventory could cost anywhere from 15 to 450 million dollars. [14]

Health concerns

Summary

Based on the body of publicly available scientific evidence, several tentative conclusions can be drawn as to depleted uranium's health effects:

• Exposure to DU can cause kidney damage in humans.
• Epidemiological evidence suggests that uranium aerosols could possibly have reproductive effects in humans.[15]
• It has been shown in rodents and frogs that water soluble forms of uranium are teratogenic or able to delay the metamorphosis (through animal experimentation).
• Evidence of human health effects caused by DU is inconclusive, due largely to the fact that the health status of only a few dozen people with verified exposures has been assessed;
• After DU munitions have been used in combat, the presence of DU and DU compounds in soil and water, or on equipment and in buildings, may – depending on a variety of factors – present short- and long-term hazards to the health of local populations.

At length

For further details see Actinides in the environment.

Depleted uranium differs from natural uranium only in its isotopic composition, not in its chemistry. As such, its chemical hazards are those which would be expected from natural uranium in the same form. The metal is pyrophoric when finely divided: in a massive form, it will slowly corrode under the influence of air and water producing uranium(V) and uranium(VI) salts.

Soluble uranium salts are toxic, though less so than those of other heavy metals such as lead or mercury. The organ which is most affected is the kidney. Soluble uranium salts are readily excreted in the urine, although some accumulation in the kidneys does occur in the case of chronic exposure. The World Health Organization 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.

The radiological dangers of pure depleted uranium are relatively low, lower (60%) than those of naturally-occurring uranium due to the removal of the more radioactive isotopes, as well as due to its long half life (4.46 billion years). The chemical toxicity of soluble uranium salts is greater than their radiological toxicity. The greatest radiological hazard is posed by inhalable dusts of insoluble uranium dioxide. However, the radiological hazards are dependant on the purity of the uranium, and there has been some concern that depleted uranium produced as a by-product of nuclear reprocessing may be contaminated with more dangerous isotopes: this should not be a concern for depleted uranium produced as tailings from initial uranium enrichment.

Due to the fact that the uranium has been chemical separated from the decay products in the recent past, the levels of radium in it will be exceptionally low. It is likely that exposure to DU will not exert as great a baneful effect upon human health as uranium ore.

The possible dangers of exposure to depleted uranium have received renewed attention as a result of the use of DU munitions in the Gulf War. Some observers believe that exposure to uranium (or any of its compounds) is the cause of, or a contributing factor to, Gulf War syndrome. Many scientists do not believe this, however. The long-term effects on populations living in the areas in which DU munitions were used have also caused some concern.

There are still more questions than answers about the health and environmental impacts of DU munitions. Nonetheless, it appears that the effects of DU are more serious than public officials would like to admit, but less harmful than asserted by hyperbolic activists.

Legal status in weapons

The legality of depleted uranium weapons has been challenged. Under the current language of the Hague or Geneva law, it is unclear if depleted uranium weapons are legal or illegal and contentious debate exists about its continued use.

Medical and scientific experts are still unsure, or not in agreement, of the mid- to long-term effects of exposure to depleted uranium. Since it is impossible at the current time to make a fully-informed assessment of the impact of this material on combatant or the civilian population, there is no consensus about whether the use of these munitions contravenes any principle or rule of international humanitarian law. Whether the use of DU munitions would be disproportionate or indiscriminate or whether they would causes superfluous injury or unnecessary suffering is a source of speculation.

Part of the problem in assessing the legality of the use of DU weapons concerns the fact that the applicable international humanitarian law generally measures the short-term rather than the medium to long-term effects of the conduct of hostilities. The assessment of whether a particular method or means of warfare is, for example, indiscriminate, is usually gauged by looking at its immediate effects and only in the context of a particular armed attack: how many civilians are killed as a direct result of the use of a particular method and means of warfare.

The law relating to the protection of the environment in armed conflicts contains some provisions that might potentially suggest the illegality of the use of DU, again however, in order to make any definitive statement in this respect, more evidence needs to be forthcoming regarding the long-term effects on the environment of these weapons, since it is not yet clear that the threshold for a finding of illegality would be met, it remains extremely difficult to reach a finding of illegality in the abstract.

The International Legality of Depleted Uranium Posted under the terms of The Creative Commons License

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

• [16] RAND review of scientific literature relating to depleted uranium as it pertains to Gulf War illnesses.
• U.S. Center for Disease Control's Toxicological Profile for Uranium (includes discussion of teratogenic and immunotoxic effects)
• 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.
• Hindin, R. et al. (2005) "Teratogenicity of depleted uranium aerosols: A review from an epidemiological perspective," Environmental Health, vol. 4, pp. 17.
• 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.
• 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.
• 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.
• Lestaevel, P. et al. (2005) "The brain is a target organ after acute exposure to depleted uranium" Toxicology, 212, 219-226.
• Depleted Uranium article from the Royal Society
• An Analysis of Uranium Dispersal and Health Effects Using a Gulf War Case Study by Sandia National Laboratories
• Depleted Uranium Human Health Fact Sheet by Argonne National Laboratory Environmental Assessment Division
• Uranium Human Health Fact Sheet
• Hindin R, Brugge D, Panikkar B., Teratogenicity of depleted uranium aerosols: a review from an epidemiological perspective, PMID 16124873

"Animal studies firmly support the possibility that DU is a teratogen. While the detailed pathways by which environmental DU can be internalized and reach reproductive cells are not yet fully elucidated, again, the evidence supports plausibility."

• Lin RH, Wu LJ, Lee CH, Lin-Shiau SY, Cytogenetic toxicity of uranyl nitrate in Chinese hamster ovary cells, PMID 7694141

"This finding indicates that uranyl nitrate has the property of causing genotoxicity and cytotoxicity in CHO cells. It appears that this cytogenetic toxicity of uranyl nitrate provides a biological basis for the potential teratogenic effect of uranium on developing fetal mice."

• Miller AC, Bonait-Pellie C, Merlot RF, Michel J, Stewart M, Lison PD., Leukemic transformation of hematopoietic cells in mice internally exposed to depleted uranium, PMID 16283518

"Intravenous injection of FDC-P1 cells into DU-implanted DBA/2 mice was followed by the development of leukemias in 76% of all mice implanted with DU pellets. In contrast, only 12% of control mice developed leukemia. Karyotypic analysis confirmed that the leukemias originated from FDC-P1 cells. The growth properties of leukemic cells from bone marrow, spleen, and lymph node were assessed and indicate that the FDC-P1 cells had become transformed in vivo. [...] These results demonstrated that a DU altered in vivo environment may be involved in the pathogenesis of DU induced leukemia in an animal model."

• S.E. Mitchell, C.A. Caldwell, G. Gonzales, W.R. Gould and R. Arimoto, Journal of Toxicology and Enviromental Health-Part A- Current Issues, 2005, 68, 951-965. (Frogs)
• M.L. Albina, M. Belles, M. Gomez, D.J. Sanchez and J.L Domingo, Experimental Biology and Medicine, 2003, 228, 1072-1077. (mice)
• A.U. Arfsten, K.R. Still and G.D. Ritchie, Toxicology and industrial Health, 2001, 17, 180-191. (Review)

Other publications

• Depleted uranium: the health debate Extract from article discussing the medical effects of depleted uranium
• "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)
• NATO Background Information on a current topic Depleted uranium
• Properties, use and health effects of depleted uranium (DU): A general overview. Journal of Environmental Radioactivity