What is Depleted Uranium and what are depleted uranium weapons?

DU weapons are weapons composed of Depleted Uranium (DU). DU is a waste product of the nuclear industry. Uranium naturally occurs as three different isotopes U234, U235 and U238. Isotopes are atoms of the same element that have different numbers of neutrons but the same number of protons. This means that they behave in the same way chemically, but different isotopes release different amounts of radiation.

The radioactive properties of DU differ from those of U-235. Unlike U238, U235 is fissionable. This means that it is so unstable that firing neutrons at it can produce a self-sustaining series of nuclear reactions in which neutrons produced by fission cause more fission and so on, releasing huge amounts of energy. This is the basis of nuclear weapons and nuclear power.

Before it is used, it needs to be concentrated as it only makes up a small proportion of naturally occurring uranium, around 0.7%. U238 makes up more than 99% of natural uranium and is much less radioactive. After natural uranium has had most of the U235 removed from it, it is called ‘depleted uranium’ i.e. uranium depleted in the isotope U235.

Depleted Uranium itself is a chemically toxic and radioactive compound, which is used in armour piercing munitions because of its very high density. It is 1.7 times denser than lead. This allows it to easily penetrate the steel armour of tanks and other vehicles when fired at high velocity.

The part of the weapon that is made of DU is called a penetrator; this is a long metal dart that can weigh more than four kilograms in the largest examples. It is usually an alloy of DU and a small amount of another metal such as titanium and molybdenum. These give it extra strength and stop it corroding.

In addition to armour-piercing penetrators, DU is also used as armour in US M1A1 and M1A2 battle tanks and in small amounts in some types of landmine (M86 PDM and ADAM). M86 PDM and ADAM landmines contain each 0,101 g of DU. 432 ADAM antipersonnel landmines were used on the Kuwaiti battlefield during the 1991 Gulf War. Both M86 PDM and ADAM landmines are still in U.S. stockpiles.

A large amount of DU in the stockpiles held in the United States has been contaminated with recycled spent nuclear fuel from nuclear reactors. For example, trace amounts of U-236 (an isotope that is only made in nuclear reactors and doesn't exist in nature) and highly radioactive substances such as plutonium, neptunium and technetium were found in a DU anti-tank shell used in Kosovo. Hundreds of thousands of tons of this contaminated stock was exported to the UK, France and other countries in the 1990s. The extent to which this DU has been contaminated with recycled spent fuel is still unknown and undisclosed. Governments have largely ignored the serious dangers this recycled fuel represents.

A common defence used by the British, US and other governments and their militaries is to claim that depleted uranium is less radioactive than natural uranium and therefore does not constitute a risk to human health. This statement is, however, misleading. In its natural form uranium is present in our environment in very small quantities as an ore, for example in rocks and soil. Conversely, the DU used by the military has been concentrated relative to background amounts, and is therefore many times more radioactive than uranium ore. In May 2003 Scott Peterson, a writer with the US newspaper Christian Science Monitor, examined radioactivity levels next to DU bullets in Baghdad and found Geiger-counter readings were 1900 times greater than background radiation levels next to DU bullets. When natural uranium is concentrated in a similar form to 'depleted' uranium it emits about 40% more alpha radiation, 15% more gamma radiation and around the same level of beta radiation. The chemical toxicity of uranium does not depend on the isotope, therefore enriched, 'natural', and depleted uranium are equally toxic chemically.

It is extremely difficult and expensive for the nuclear industry to store DU. It is thought that the US currently has 1 billion tonnes of depleted uranium radioactive waste, while the UK has at least 50,000 tonnes. With both countries and dozens of others worldwide about to embark on a new generation of nuclear power stations, this waste burden is set to increase dramatically, in turn increasing the pressure on governments to dispose of DU elsewhere.

The waste is stored in cylinders many sites across the world and is vulnerable to corrosion and leaks owing to ageing cylinders and outside storage. It is stored mainly in the form of depleted uranium hexafluoride (DUF6) which can leak if the corroding cylinders are breached. At least 10 cylinders are known to have breached during the past 10 years. DUF6 is extremely toxic and corrosive and represents a major health hazard.

Turning this DU waste into weapons solves some of the problems faced by governments and the nuclear industry, concerning what to do with these large stockpiles. Not only is DU practically free of charge for the arms manufacturers, but it no longer has to be stored and monitored indefinitely.