Britain said that together with its Challenger 2 tanks, it would also be sending Ukraine armour-piercing shells containing depleted uranium.
Britain said that together with its Challenger 2 tanks, it would also be sending Ukraine armour-piercing shells containing depleted uranium (DU).
Russian President Vladimir Putin accused London of proliferating "weapons with a nuclear component", comments Britain labelled "disinformation".
So, what are these depleted uranium shells? And are they related to nuclear weapons?
What is depleted uranium?
The isotope U-235 is extracted from natural uranium ore and used both as fuel for reactors and in nuclear weapons. This process is called enrichment. But the content of the "useful" isotope in the ore is insignificant - about 10 per cent. The remaining 90 per cent of the isotope contains negligible amounts of U-235, which consist mainly of the slightly radioactive U-238. This is depleted uranium which can be described as waste from the enrichment process.
Why use depleted uranium in projectiles?
Depleted uranium is very dense. This means that it is much heavier than, for example, steel shells of the same size. The force of energy, therefore, is very strong, enabling it to penetrate armour.
Depleted uranium does not explode, but it is pyrophoric - small fragments that can penetrate armour can easily be ignited. So, a projectile made of this material is an armour-piercing incendiary material.
And since this material is, in fact, uranium enrichment waste, it is relatively cheap and available in large quantities in countries with a developed nuclear industry.
These qualities attracted the US military in the early 1970s when it became necessary to find ways to counteract the new generation of Soviet tank armour.
The US mostly abandoned the use of other metals for armour-piercing cores. Depleted uranium is used not only in tank shells but also in high-speed smaller calibre guns of 25-30mm, which are used on Infantry-Fighting Vehicles (IFV) and attack aircraft.
During the 1980s and 1990s, such ammunition entered the armament of other countries as well, including the United Kingdom and what was then the Soviet Union.
Where have depleted uranium projectiles been used?
The US first used them during Operation Desert Storm in 1991. According to the Pentagon, American and British tanks fired several thousand such shells and their aircraft fired hundreds of thousands.
The Pentagon acknowledged that such shells were then used in the former Yugoslavia, Iraq, and Syria. Some experts believe the evidence points to the use of DU in Somalia in the 1990s and in Afghanistan after 2001, although this has never been confirmed by officials.
Is the supply of British shells to Ukraine legal?
Depleted uranium is not subject to nuclear non-proliferation rules. Therefore, in terms of international law, DU shells are no different from any other. Nor are there any agreements that would regulate the supply of them specifically.
That is why, according to Western experts, Moscow's protests are groundless - bearing in mind that Russian tanks have also been carrying depleted uranium shells since at least the early 80s.
John Erath, a Senior Policy Director at the Center for Arms Control and Non-Proliferation told Euronews:
"They're not considered nuclear weapons. They do not have a nuclear component. And so they are not covered by nuclear non-proliferation treaties. They would be subject to the same export control restrictions as any conventional munition. So, the Russian statement that this is somehow transferring a nuclear capability is completely incorrect."
But Erath said the Kremlin could still use the supply of these shells to Ukraine as an "excuse" to threaten to use its own nuclear weapons.
"Russia is saying, by using something that a willing mind might connect to nuclear weapons, that increases the chance that we, Russia, would use a nuclear weapon. So this has been a pattern almost since the beginning of the war, where we see these threats that continued support by the West to Ukraine could lead to the use of nuclear weapons. And it's the West putting the world on that horrible path. So, this is highly irresponsible, but it's a tactic that the Russian government has used repeatedly."
So is depleted uranium dangerous?
DU is much less radioactive (by about 40 per cent) than uranium ore, let alone purified U-235. Furthermore, in tank shells, the core itself is covered by a sabot and fairing. The military claims that prior to firing, such projectiles are safe, as long as the most basic safety rules are observed: weak radiation is unable to penetrate skin and clothing.
However, if such a "pin" penetrates armour, a cloud of tiny fragments or dust, is produced. It is this radioactive and toxic dust - consisting to a large extent already of uranium oxides - that poses a danger both to the crew of the affected vehicle, as the dust can enter the lungs and digestive tract, and to civilians, as it can enter the soil and water.
The first studies on the dangers of uranium dust emerged in the mid-1990s, following Desert Storm, where DU shells were used for the first time and in very large quantities.
Several dozen American tanks and IFVs were incapacitated by "friendly fire" - American DU shells. The number of American soldiers who were wounded - or somehow came in contact with uranium dust - could be as high as 170.
It was then that papers appeared which did not rule out that depleted uranium could be one of the causes of "Gulf War Syndrome" - the chronic, poorly-explained varied ailments of ex-soldiers.
Operations in the former Yugoslavia led to talk of the "Balkan syndrome" and once again depleted uranium was cited. Tens of thousands of aircraft rounds were left in equipment debris and soil. Then, soldiers from several European countries fell ill. Leukaemia deaths were reported - in the Belgian contingent alone, five died suddenly.
The use of DU rounds in the Balkans in the mid-1990s was only revealed in 2001. Belgium, Germany, Italy, and France approached Washington demanding explanations. But, the military insisted that the shells were safe.
In 2001, the USA conducted research on military veterans and concluded that depleted uranium in a quantity considered dangerous had not been found in the bodies of wounded soldiers.
Germany conducted its own research. Tests on 120 soldiers who had served in Kosovo showed no deviations from the age norm.
In 2009, an Italian court ordered the country's defence ministry to pay a hefty compensation - €1.4 million – to the family of a soldier who fell ill with cancer and died after serving in Somalia in the early 1990s. The death was attributed to depleted uranium.
A number of organisations have been calling for a ban or restriction on the use of DU projectiles since the early 2000s. According to activists, while the health of soldiers is sometimes discussed, the possible long-term effects on civilians who return to the land where the battle was fought - for example in Iraq, where such projectiles have been used in huge quantities during two wars (in 1991 and since 2003) - are completely out of the question.
Here, too, other experts think the danger of the bombs is exaggerated, at least in Ukraine, where we are talking about 14 British Challengers and a few dozen or so rounds:
"Battlefields are going to be contaminated and they're going to suffer devastating environmental consequences anyway,” said Erath. “What the depleted uranium rounds would add would be minimal. The environmental problems created by a war are so extreme that that should be what people are worried about and not the addition of a few depleted uranium projectiles."
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