Depleted Uranium: Origin, Properties and Uses

Reference article · Updated 2026-11-06

Key facts

DU is uranium whose U-235 share is below the natural 0.711 percent; enrichment tails typically hold roughly 0.2 to 0.3 percent.
Metallic DU is about 1.7 times as dense as lead, which explains most of its industrial and military uses.
DU carries roughly 60 percent of the radioactivity of natural uranium of the same mass, according to WHO.
UNEP and WHO field and desk assessments have examined DU health and environmental questions since 2001.
Large amounts of DU are held as depleted uranium hexafluoride, a by-product of enrichment.

What counts as depleted uranium

Natural uranium is a mixture of isotopes in which U-238 makes up more than 99 percent and the fissile isotope U-235 about 0.711 percent. Reactor fuel for most commercial power plants must contain more U-235 than that, so uranium is enriched before it is fabricated into fuel. Every enrichment step produces two streams: a smaller product stream richer in U-235 and a much larger waste or tails stream that is poorer in it. Uranium in the tails stream is called depleted uranium.

The US Nuclear Regulatory Commission defines depleted uranium in its regulations as uranium containing less than 0.711 percent U-235 by weight. In practice the tails assay chosen by an enrichment plant is a commercial decision, and material leaving a plant commonly carries around 0.2 to 0.3 percent U-235. The US Department of Defense has stated that the DU it uses contains about 0.2 percent, and sources quote slightly different figures depending on the stream. For the arithmetic of how much tails a given amount of fuel creates, see the nuclear fuel cycle mass-balance page.

DU is not a separate element or a nuclear waste in the strict sense that spent fuel is. It contains almost no fission products. Chemically it is uranium, and the radiological and toxicological information on natural uranium applies to it with adjustments for its isotopic make-up.

Where DU comes from

Both historical enrichment technologies, gaseous diffusion and gas centrifuges, work on uranium in the form of uranium hexafluoride (UF6). The tails therefore leave the plant as depleted UF6, which is typically stored in steel cylinders in the open at the enrichment site. UF6 is chemically reactive with moisture, so many countries and operators have chosen to convert it into the more stable oxide U3O8 or to keep it under monitored storage until a use or disposal route is available. The inventories held in the United States and elsewhere are discussed on the stockpiles page.

DU metal is made from this material by converting the hexafluoride to uranium tetrafluoride and reducing it with an active metal, followed by casting and machining. Only a small share of the accumulated tails has ever been converted to metal. Most of the world inventory remains as hexafluoride or has been converted to oxide for storage.

Other routes exist in principle. Depleted uranium can be re-enriched when uranium prices or enrichment costs make it economic, and some operators have re-enriched older tails to extract further U-235. It can also be blended with high-enriched uranium to produce low-enriched fuel. These activities are described in general terms on the enrichment page.

Physical and chemical properties

Metallic uranium has a density of about 19 grams per cubic centimetre. An NRC-hosted technical paper describes it as roughly 1.7 times as dense as lead, and one commonly cited value is 19.1 g/cm3. Uranium metal is also pyrophoric in fine particles: finely divided DU can ignite in air, and a solid penetrator that fragments on impact can produce burning particles and oxide dust. Corrosion produces oxides that can differ in solubility, which matters for how the body handles inhaled particles.

Property	Natural uranium	Depleted uranium
U-235 content	about 0.711 percent	below 0.711 percent; commonly about 0.2 to 0.3 percent
U-238 content	about 99.3 percent	more than 99.3 percent
Radioactivity per unit mass	reference value	roughly 60 percent of natural uranium (WHO)
Main hazard type	chemical toxicity and weak alpha radiation	same, with slightly lower radiological contribution

The radioactivity drops because U-234, which is concentrated alongside U-235 in enrichment, is removed along with it. Depleted uranium is mainly an alpha emitter. Alpha particles are stopped by skin or a sheet of paper, so external radiation is minor except in direct, prolonged contact with large metal masses. Inhaled or ingested material is the relevant pathway. For the units used in dose comparisons, see the radiation units converter.

Uses of depleted uranium

The unusual density of DU is the reason it has found limited commercial use despite being a plentiful by-product. An NRC-hosted overview lists three main uses of the metal: armour-piercing projectiles for military ordnance, radiation shielding and aircraft counterweights. It describes military ordnance as by far the largest use.

Penetrators. Kinetic-energy rounds made of DU alloys combine high density with a tendency to keep a sharp profile as they penetrate armour, and with a tendency to ignite on impact.
Armour. Some armoured vehicles have used DU in or behind armour plate, again for density. Which vehicles and in what quantity is a matter for national defence publications.
Counterweights. High density lets a counterweight be small relative to a control surface, which is why DU was used in some aircraft.
Shielding. Dense materials attenuate gamma rays, so DU has been used in shielded containers for radioactive sources and transport casks.

The military use of DU, and the documented history of its use in Iraq, is covered separately in the Iraq page.

Health questions: what major bodies have said

The health discussion has two parts. First, uranium is a heavy metal, so high intake can damage the kidneys; this chemical effect is generally of more concern than the radiation for soluble uranium compounds. Second, insoluble oxide particles lodged in the lungs or in tissue, or fragments embedded in the body after an injury, deliver alpha radiation locally over long periods.

WHO published a monograph on DU sources, exposure and health effects in 2001 and sent a mission to Kosovo in the same year. Its assessments concluded in general that for most people in post-conflict areas intakes would be low and that adverse effects would not be expected from them, while stressing that people who handle damaged vehicles or contaminated sites, and children who play there, deserve specific attention.

WHO's current radiation page continues to describe DU as a by-product of enrichment and covers sources of exposure and precautions. A US Department of Defense health page citing a US toxicological profile notes that no human cancer has been seen from exposure to natural or depleted uranium; this reflects the state of evidence in that document and not a statement that every question is settled.

Concerns of affected communities, particularly in Iraq, and the uncertainty of data in conflict settings are discussed on the Iraq page. Readers should treat claims from advocacy sources on either side with care and consult the institutional reports listed below.

Regulatory and policy status

In the United States, DU is regulated as source material under NRC rules, with the definition in 10 CFR 40.4. Military stocks held by the Department of Defense fall under that department's own radiation-safety rules. Elsewhere, national nuclear regulators treat depleted uranium as a radioactive material subject to licensing, transport rules and waste-classification schemes; the details differ by country, and the regulation overview gives the general picture.

At the international level there is no treaty that specifically bans DU munitions. The UN General Assembly has, since 2007, adopted a series of resolutions on the effects of armaments and ammunition containing depleted uranium. The most recent one verified for this page, A/RES/79/49, was adopted on 2 December 2024 by 152 votes in favour, 4 against and 30 abstentions. These resolutions ask for information, for assistance to affected states and for further study, and do not themselves prohibit any weapon. More detail is on the Iraq page.

UNEP has contributed to the evidence base through post-conflict assessments of DU in Kosovo (2001), Serbia and Montenegro (2002) and Bosnia and Herzegovina (2003). UNEP described the Balkan results as showing no immediate risks under the conditions found there while recognising open scientific issues, such as long-term groundwater effects near penetrators.

Frequently asked questions

Is depleted uranium nuclear waste?

It is a by-product of enrichment and in several countries is classified as radioactive material or, when no use is foreseen, as waste. It contains almost no fission products, unlike spent fuel.

How radioactive is depleted uranium compared with natural uranium?

WHO states that it carries roughly 60 percent of the radioactivity of natural uranium for the same mass, because the U-234 and U-235 removed in enrichment contribute much of the activity.

Why is DU used in munitions?

Mainly because it is very dense, about 1.7 times as dense as lead, and it is a plentiful by-product. Dense penetrators concentrate energy on a small area when they strike armour.

What do WHO and UNEP conclude about health risks?

Their Balkan-era assessments found low exposures for most people and no immediate widespread risk, while identifying groups needing attention and uncertainties that deserve follow-up.

Is DU banned under international law?

No treaty specifically bans it. UN General Assembly resolutions call for study, information sharing and assistance but are not binding prohibitions.