Why on Earth is Depleted Uranium Used for Military Ammunition?

In the opening of the 2012 James Bond film Skyfall, everyone’s favourite super spy chases an assassin through the streets of Istanbul to recover a hard drive containing the identities of undercover British agents. For his trouble, he receives a shoulder full of shrapnel from the assassin’s pistol, is accidentally shot by a fellow agent, and falls off a bridge to his presumed death – whoopsie doodle. But this being a James Bond film, he inevitably returns to duty and, after digging the shrapnel out of his shoulder, discovers that the assassin’s bullets are made of depleted uranium. This handily allows him to identify and track down the assassin, kicking off the rest of the plot. But unless the assassin’s intention was to leave an easily-traceable calling card, he really needn’t have bothered with such fancy ammunition. For while depleted uranium projectiles are a real thing, the destructive properties of this very expensive material are wasted on something as small as a pistol bullet. So what is depleted uranium, anyway, and why is it used in military ammunition? Let’s lock and load and find out, shall we?

Depleted uranium, also known as DU or depletalloy, is uranium which contains less than the natural amount of the isotope U-235. Natural uranium consists mainly of the Isotope U-238, with only 0.72% being U-235. The only exception is uranium found at the Oklo mine in Gabon, Africa. Here, 2 billion years ago, Uranium deposits in the ground underwent a natural nuclear chain reaction, consuming most of the U-235. However, most depleted uranium is a byproduct of uranium enrichment, wherein the proportion of U-235 in Uranium metal is increased so the resulting fuel can be used nuclear reactors and weapons.

Depleted uranium typically contains 0.3% U-235 or less and has a density of 19.1 grams per cubic centimetre, making it the seventh densest metal after gold, tungsten, plutonium, neptunium, platinum, iridium, and osmium. This high density makes it ideal for use in high-velocity armour-piercing projectiles, as a DU penetrator can have a smaller cross-sectional area than a steel projectile of the same weight. This reduces aerodynamic drag, allowing for higher velocities; and concentrates the kinetic energy of the projectile onto a smaller area, improving penetration.

But DU also has two rather more unique properties. While most metal projectiles flatten on impact, increasing their cross-sectional area and decreasing their penetrating ability, DU projectiles fracture in a manner that makes them self-sharpening, allowing them to maintain their penetrating power all the way through the target. Uranium is also pyrophoric, meaning that it spontaneously ignites in air when ground into a fine enough powder. This, coupled with DU’s inherent brittleness, means that once a DU projectile has penetrated a tank’s armour, it disintegrates into a white-hot shower of fragments that can destroy equipment, ignite ammunition and fuel stores, and generally ensure that everyone inside the vehicle has a very bad day. And while DU is not nearly as hard as tungsten (the usual go-to metal for armour-piercing ammunition) it can be hardened by alloying it with titanium or molybdenum and carefully heat-treating it to produce one large metallic crystal.

But perhaps DU’s greatest advantage is its sheer availability. In the United States, uranium enrichment for use in reactors and weapons over the last half-century has generated nearly 700,000 metric tons of depleted uranium, all of which has to be stored and monitored by the federal government. Making armour-piercing ammunition is one way of reducing this stockpile. DU’s density also makes it useful in a number of other applications, such as radiation shielding for nuclear reactors and medical imaging, balancing weights on fixed-wing aircraft and helicopter rotors, and armour plating on tanks such as the American M1A1 and M1A2 Abrams. It is also used in the casing of the B61-11 bunker-busting bomb to improve penetration into the earth.

DU penetrators are mainly used in cannon rounds of 30mm and up, for in smaller, lower-velocity weapons – like, say, a pistol – DU’s penetrating ability would be wasted. In US service, DU rounds are used in the Phalanx 25mm Close-In Weapons System or CIWS [“sea-whiz”] used to protect US Navy ships from incoming missiles; the 25mm M424 cannon used on the Bradley and LAV-25 armoured fighting vehicles; the 25mm GAU-12 Equalizer and 20mm M197 rotary cannons used on the AV-8B Harrier jump jet and AH-1 Cobra attack helicopter; and in 105 and 120mm projectiles fired by the M1 Abrams tank. Internationally, DU penetrators are also used in 120mm rounds fired by the British Challenger 1 and 2 tanks and the 125mm 3BM59 Svinets-1 and 3MB60 Svinets 2 rounds fired by Russian tanks like the T-80. Today, companies in 5 countries – the United States, the United Kingdom, France, Russia, and Pakistan – are known to produce DU ammunition.

However, perhaps the most famous use of DU is in the 30mm PGU 14/B rounds for the GAU-8 Avenger rotary cannon carried by the Fairchild-Republic A-10 Thunderbolt II – AKA the “Warthog”. Weighing 395 grams, these rounds comprise a lightweight aluminium shell wrapped around a smaller DU penetrator and can achieve a muzzle energy of just over 200 kilojoules – enough to penetrate the thinner top armour of most modern tanks. Furthermore, the GAU-8 can deliver these projectiles at a blistering rate of 3,900 rounds per minute. At these speeds, it would take only 18 seconds of continuous firing to use up the A-10’s ammunition supply, though in practice pilots are limited to firing 2-second bursts to conserve ammunition and avoid overheating or wearing out the gun.

Depleted uranium ammunition made its combat debut during the Gulf War of 1990-1991, during which Coalition forces fired some 350 tons of DU against Iraqi targets over the course of six months. Some 10 tons of DU was also fired by NATO forces in Bosnia in 1994-95 and Kosovo in 1998-99; and 2,000 tons by US forces during the 2003 invasion or Iraq. Yet despite widespread claims by the US military, DU is not some magical tank-killing secret weapon; indeed, relatively few tanks were actually destroyed by depleted uranium rounds during these conflicts. During the Gulf War, for instance, of the 1,000 Iraqi tanks destroyed by A-10s, 900 were destroyed using the AGM-65 Maverick missile, not the GAU-8; while of the remaining 2,700 tanks destroyed by helicopters, tanks, and ground forces, only 45 were hit by DU rounds – a kill rate of less than one in seven. Some of this ineffectiveness has to do with the inherent inaccuracy of the GAU-8, exacerbated by the practice of flying at high altitudes to avoid anti-aircraft fire. However, even under ideal conditions, the A-10’s performance leaves much to be desired. On November 7, 1979, the US Air Force conducted a live-fire demonstration of the A-10 at Nellis Air Force Base in Nevada. For this test, ten M47 Patton tanks of 1950s vintage were arranged on the ground in a triangular formation to simulate a column of similarly-sized Soviet T-62 tanks on the move. The pilot then made 10 passes at the target – one for each tank – and fired a total of 174 rounds. Yet despite these near-ideal conditions – clear skies, a stationary target, and no antiaircraft fire – only 90 rounds hit their targets, with only 30 of these achieving penetration. 3 tanks were declared destroyed, 3 were immobilized by hits to the tracks and suspension systems, while 2 were completely unscathed. But this already marginal result was made worse by several factors. First, in a real combat situation, the presence of antiaircraft defence vehicles like the ZSU-23-4 Shilka would have limited the pilot to a single pass. The moving tank column would also have made aiming more difficult. Even worse, by the time the test was conducted the M47 was hopelessly outdated; had the targets been more modern M60 tanks, the report concluded, only one would likely have been destroyed. And had they been even more advanced Soviet T62s – the very tanks the targets were meant to represent – none would have been destroyed. Indeed, during the Gulf War, twenty Coalition vehicles were hit by DU rounds in friendly fire incidents, with 90% of their crews surviving. So while DU certainly has its advantages, it is far from the “magic bullet” its proponents claim it to be.

But the infamy of depleted uranium rounds lies less in their mythical tank-busting ability but rather their supposed long-term toxic effects. Indeed, DU contamination has been widely posited as at least one cause of so-called “Gulf War Syndrome”, a cluster of chronic symptoms including fatigue, muscle pain, insomnia, and impaired cognition afflicting nearly 250,000 US veterans of the 1990-1991 conflict. Following the Kosovo war in 1999, British biologist Roger Coghill claimed that DU contamination was likely to cause an 10,000 extra cancer deaths in Serbia, while more recently the use of DU munitions around the Iraqi city of Fallujah has been blamed for a steep rise in leukemia, liver and kidney disease, miscarriages, and serious birth defects among the local population. According to local physician Dr. Samira Alani:

“Between 2002 and 2005, the US armed forces expended six billion bullets [around Fallujah] – according to the figures of the US General Accounting Office…[these rounds create] fine metal-containing dust particles as well as DU-containing particles that persist in the environment. These particles can enter the food chain and enter the human body via contaminated food. Toxic particles can also become airborne with the wind and be inhaled by the public. Iraq is prone to frequent sand and dust storms. Continuous public inhalation of toxic materials can lead to cancer. Ingested or inhaled particles that emit alpha radiation can cause cancer.”

In 2010, Alani co-authored a study revealing that the rate of heart defects in Fallujah had risen to 13 times that in Europe, while between October 2009 and December 2011 she personally logged 699 cases of severe birth defects in the city – including cases of spina bifida, hydrocephalus, and even babies born with multiple limbs and heads. Meanwhile, official Iraqi statistics show that between 1991 and 2005, the cancer rate throughout Iraq rose 40 times from 40 to 1,600 out of every 100,000 people. This has led another Iraqi doctor, Huda Ammash, to compare DU contamination in Iraq to “100 Chernobyls.”

But is it true? Is depleted uranium actually responsible for all these illnesses? At first glance, the link appears plausible. Depleted uranium is only around 60% as radioactive as natural uranium and emits mostly alpha radiation, which cannot penetrate human skin and is largely harmless outside the body. However, if uranium dust enters the body via inhalation, ingestion, or wound contamination, the large amount of energy deposited by alpha particles directly into the tissue can cause severe genetic damage and cancer. Worse still, the main constituent of DU, uranium 238, has a half-life of 4.5 billion years. As a heavy metal, uranium is also toxic in and of itself, and like lead and cadmium can accumulate in the bones, liver, and kidneys, causing long-term damage to these organs and the central nervous system. And making the link between DU munitions and chronic health effects even more probable, the fine dust generated by the impact of DU projectiles is very easily absorbed into the body.

Yet, despite this, there is almost no evidence that DU contamination is directly responsible for any cases of cancer or long-term illness among combat veterans or residents of war zones. Following the Kosovo War, a study of 122 German soldiers deployed in the region revealed that none had incorporated any DU into their bodies, while similar studies on soldiers of other nationalities as well as residents of Bosnia-Herzegovina and Bosnia returned similar results. And in the early 2000s, a team from the United Nations Environment program’s Post Conflict Assessment Unit and a committee of 50 nations set up by NATO both concluded that soldiers who were possibly exposed to DU dust suffered chronic illnesses at a rate no higher than those who were not exposed. Likewise, a 2021 study conducted by the University of Portsmouth in England concluded that DU contamination was not responsible for Gulf War Syndrome; while a 2013 study found that not only was DU not responsible for the rise in chronic illnesses in Fallujah, but that no traces of the material could be found anywhere in the city’s soil.

Much of this discrepancy stems from an overestimation of the contamination risk posed by depleted uranium. For despite the large quantities of DU ammunition expended during the Gulf War, Balkan Wars, and Iraq invasion, very little entered the environment in a form that could easily cause contamination. For instance, during the Gulf War, 86% of DU rounds were fired by aircraft, which when firing at ground targets typically achieve a hit rate of only 5-10% . Furthermore, only about 20% of each projectile is vaporized on impact. Thus, of the 350 tons of DU fired during the Gulf War, only around 7 tons would have been converted into dust – and most of that would have been concentrated inside the targeted vehicles, making it unlikely to be dispersed into the environment. Meanwhile, the projectiles that missed would largely have landed intact in the soft ground and thus pose little long-term contamination risk.

And even if soldiers and civilians had been exposed to large quantities of uranium dust, there is little evidence that this would have impacted their health either. Indeed, a US Centres for Disease Control review of 11 studies on uranium miners found no link between exposure to uranium dust and cancer, with all recorded instances of chronic illness being attributed to exposure to radon gas – a decay product of uranium – and other toxic substances in the mine. A 1999 literature renew by the RAND corporation similarly concluded that:

“No evidence is documented in the literature of cancer or any other negative health effect related to the radiation received from exposure to depleted or natural uranium, whether inhaled or ingested, even at very high doses.”

Thus, Huda Ammash’s comparison of DU contamination in Iraq to “100 Chernobyls” is a gross exaggeration, and the sharp spike in chronic health problems in Falljuah is likely caused by other factors, such as non-radioactive heavy metals and other toxic materials released by regular munitions.

Despite this, many groups have pushed for DU projectiles to be banned, with the Yugoslav government even arguing in June 1999 that the use of such weapons was an act of genocide due to the potential long-term effects of DU contamination on the Yugoslav people. Others have pointed to Article 35 of Protocol I of the Geneva Conventions, which prohibits any means or methods of warfare that cause superfluous injuries or unnecessary suffering. However, the US military has countered these claims by arguing that DU rounds are solely designed to defeat armoured vehicles via kinetic and incendiary effects – thus making them perfectly legal under international law. Nonetheless, several branches of the US Armed Forces as well as many foreign militaries have begun slowly abandoning DU ammunition. In 1989, the US Navy announced that it would phase out DU shells in its Phalanx CIWS systems in favour of more conventional tungsten ammunition, which meets performance requirements without any potential health and environmental risks. In 2002 and 2008, the British Army and the US Marine Corps also announced the replacement of DU rounds with tungsten on its armoured fighting vehicles, with the latter stating:

“We’re not considering depleted uranium anymore because of the environmental problems associated with it, be [they] real or perceived.”

But while depleted uranium weapons may not be a tank-killing “magic bullet” nor a radioactive disaster waiting to happen, you still wouldn’t want to find yourself on the receiving end of one. So if ever you see the menacing shape of an A-10 Warthog swooping down towards you, it’s probably best to take cover.

Expand for References