It seems that every time uranium gets mentioned, hyperbole soon follows. Ukrainian media accounts in recent days have noted the discovery of a Russian munition containing depleted uranium (DU). This has ignited social media commentary that seems somewhat depleted of facts. The weapon in question is an R-60M air-to-air missile: a fairly venerable 1980s-vintage munition that has been seen in a number of conflicts around the world.

What is DU? Despite the name or the conspiratorial folklore, it is not expended nuclear reactor fuel. DU is the by-product of the process of enriching natural uranium into fissile material. It consists almost entirely of metallic uranium 238: the non-fissile and mildly radioactive isotope of uranium. A reasonable factsheet on DU is here. Countries with a nuclear fuel refining capability tend to build up reserves of thousands or even hundreds of thousands of tonnes of this by-product, so for countries like the United States and Russia it is effectively free. Over a million tonnes are sitting around worldwide. There are numerous civilian uses for DU due to the density of the metal. It is commonly used in radiological shielding in medical facilities, being denser than lead by a factor of 1.68. It has also been used as a counterweight material in structures like wingtips. Indeed, the amount of DU in the ailerons of a 1980s-era Boeing 747 airliner was equivalent in weight to the DU content of dozens of US 120 mm tank rounds.

DU gets used by some countries in weapon systems due to the physical properties of uranium metal. DU’s density means that, for a particular physical size of projectile, a DU projectile would have significantly more kinetic energy. It does not mushroom like lead and DU also has less tendency to shatter or splinter, unlike tungsten: another dense metal that can be used in such applications.

Finally, uranium metal is pyrophoric, meaning that it can ignite at higher temperatures. These properties mean that if you want some sort of bullet or projectile that can pierce through armour while also burning very hot, DU has good properties. It should also be noted that DU has been incorporated into armour, most notably the US military’s M1-series main battle tanks (MBTs).

Several countries have fielded DU munitions over the previous decades. The US, UK, Pakistan, China, the Soviet Union and then Russia, and France are all known to have made DU weapons at some point, but perhaps a dozen others have incorporated them into their arsenals through the international arms trade. DU munitions, not without controversy, have been sent to Ukraine to aid in its defence.

There are two categories of DU munitions that have seen the most use in recent decades: automatic cannon rounds in 25 mm (used by the M2 Bradley Fighting Vehicle) and 30 mm (used by the A-10 attack aircraft) to deliver an anti-tank capability; and larger-bore 105 mm and 120 mm discarding-sabot rounds developed for use in MBTs (such projectiles are basically large solid metal darts made of DU).

The Soviet/Russian R-60M, meanwhile, is more of a design outlier. It spreads a web of DU rods to increase the effective radius of the air-to-air munition, as only one tiny piece of it would likely need to hit a target.

Despite uranium’s association with both nuclear power and nuclear weapons, depleted uranium is not terribly radioactive. The radiation is principally from alpha particles, which only travel a few centimetres in air. For there to be enough DU to provide acute radiation hazards, one would literally need freight trainloads of the stuff for the maths to work out (see the previous Warsight article on detecting uranium.) It is factually incorrect to refer to DU weapons as ‘dirty bombs’ or ‘nuclear weapons’ because the radiation is simply insufficient.

The primary hazard from DU is due to its properties as a heavy metal poison, not dissimilar in some ways to lead and mercury poisoning. One really does not want to get DU into one’s body, and it does not have an easy metabolic pathway out of the body once it gets in. There are numerous papers and studies identifying the possible long-term health effects posed by DU, including this good overview. Vehicles and other targets destroyed by DU munitions are often heavily contaminated with fragments, debris and dust. Likewise, an armoured vehicle that contains DU in its armour could be a source of contamination. The US military has enacted safety procedures for this, while there have been many studies of environmental health effects in places like the former Yugoslavia and Iraq. There are numerous claims and some counterclaims, as well as both controversy and conspiracy theories at play, but the weight of the evidence seems to be that local contamination has been a problem.

It should be noted that unused or malfunctioning DU munitions, like the one seen in Ukraine, pose little hazard except to the handler – and even then only if poorly handled. It is important not to exaggerate the characteristics of such weapon systems. They are environmentally problematic but not a significant radiological threat.