depleted uranium

depleted uranium
Name	Depleted uranium
Category	Actinide
Atomic number	92
Mass number	238
Density	19.1 g/cm³
State	Solid
Appearance	Silvery-gray metal

depleted uranium is a dense, weakly radioactive metal largely composed of the uranium isotope with mass number 238. It is produced as a byproduct of uranium enrichment processes used to make nuclear fuel and nuclear weapons material, and it has found applications in both Ballistics and industrial radiography. The material's high density and pyrophoric properties have driven debate involving public health advocates, militaries, and international organizations.

Composition and Properties

Depleted uranium is primarily uranium-238, with reduced concentrations of uranium-235 and traces of uranium-234, created through isotope separation operations at facilities such as Paducah Gaseous Diffusion Plant, Capenhurst, and Uranium Enrichment Corporation of China. As an actinide metal related to thorium and plutonium, it exhibits high density (~19.1 g/cm³), hardness greater than lead, and a melting point near 1132 °C. Chemically it forms oxides (notably UO2 and U3O8) when exposed to air and water; these oxides and metal particulates are the main chemical species considered in exposure scenarios investigated by organizations like the World Health Organization and the International Atomic Energy Agency. Depleted uranium emits primarily alpha radiation from uranium-238 decay chains and minimal gamma/neutron radiation, which underlies considerations by radiological protection bodies such as the International Commission on Radiological Protection.

Production and Sources

Major sources are cascades at enrichment plants performing gaseous diffusion or gas centrifuge operations, historically at sites including Oak Ridge National Laboratory, Urenco facilities, and Soviet-era complexes like Mayak. During enrichment of natural uranium for fuel or weapons, the heavier 238 isotope is left behind; stockpiles have accumulated in national inventories managed by entities such as the United States Department of Energy, Rosatom, and the European Commission. Depleted uranium also arises from reprocessing spent fuel at installations like Sellafield and storage operations at depots used by military organizations including the United States Army and British Army. Commercial markets for DU have included sales to defense contractors and manufacturers in countries such as United States, United Kingdom, Russia, France, and India.

Military and Civilian Uses

The material’s high density has made DU attractive in kinetic energy penetrators, notably in armor-piercing rounds produced by firms like General Dynamics and used by armed forces during conflicts such as the Gulf War, the Kosovo War, and the Iraq War. Depleted uranium rounds are valued for long-rod penetrator designs and for adiabatic shear behavior that aids armor defeat, employed by platforms including the M1 Abrams, Leopard 2, and Challenger 2 main battle tanks. Civilian applications have included counterweights and radiation shielding in medical devices at institutions like Massachusetts General Hospital and in industrial radiography sources for companies such as Siemens. DU has also been used experimentally in aircraft ballast and in naval applications by navies such as the Royal Navy.

Health and Environmental Effects

Concerns focus on chemical toxicity as a heavy metal and radiotoxicity from alpha-emitting decay products; investigations have been undertaken by bodies including the World Health Organization, the United Nations Environment Programme, and the European Environment Agency. Exposure pathways studied in incidents and epidemiological work involve inhalation of aerosols generated when penetrators impact armor, ingestion of contaminated soil or water near sites like firing ranges at former bases such as Gulfport and Dugway Proving Ground, and dermal contact. Health endpoints evaluated include nephrotoxicity, potential carcinogenicity assessed by panels such as the International Agency for Research on Cancer, and reproductive effects examined by researchers at institutions like Johns Hopkins University and Imperial College London. Environmental fate studies by agencies such as the United States Environmental Protection Agency and Norwegian Radiation Protection Authority analyze soil mobility, groundwater contamination near storage sites, bioavailability to species monitored by organizations like World Wildlife Fund, and long-term persistence in ecosystems.

Regulation and International Law

Regulatory oversight spans national authorities—e.g., the United States Nuclear Regulatory Commission, Environment Agency (England and Wales), and Rosatom—and international frameworks that address conventional weapons and radiological safety, including relevant provisions within the Convention on Certain Conventional Weapons discussions and reporting to the International Atomic Energy Agency. Some states and municipal bodies have adopted restrictions or moratoria influenced by resolutions in forums such as the United Nations General Assembly and debates in the European Parliament. Stockpile management, transport, and disposal of depleted uranium are subject to national hazardous-waste statutes and to international guidelines on radioactive material packaging promulgated by the International Maritime Organization and the International Civil Aviation Organization.

Controversies and Incidents

High-profile controversies have accompanied the deployment and storage of depleted uranium in contexts such as post-conflict contamination in Kuwait, Kosovo, and parts of Iraq; incidents of DU munitions use during the 1991 Gulf War and the 2003 invasion of Iraq prompted inquiries by bodies including the United Nations Environment Programme and sparked litigation in national courts like those in the United Kingdom and Italy. Activist organizations such as Greenpeace, International Physicians for the Prevention of Nuclear War, and Human Rights Watch have campaigned for bans, while defense establishments and manufacturers have defended DU use citing performance and existing risk assessments by the National Research Council and military research laboratories such as DRA and U.S. Army Research Laboratory. Notable contamination incidents at testing ranges and storage sites have led to remediation projects overseen by agencies including the United States Department of Defense and national environmental ministries.

Category:Uranium