Unexploded ordnance from World War II is becoming more dangerous

A study of unexploded bombs from World War II found that one of the explosives they contained had become shock-sensitive and could ignite if dropped during disposal. The explosive, called Amatol, was widely used during World War I and World War II and is still included in some of the ammunition used during Russia’s war in Ukraine.

“Based on our findings, we can say that it is relatively safe to handle, but it cannot be treated like TNT,” says Geir Petter Novik of the Norwegian Defense Research Establishment. “In contrast to TNT, it can definitely explode if dropped.”

There are millions of tons of unexploded ordnance around the world, some in old ammunition dumps and some in artillery shells and bombs that did not explode after being fired or dropped. Novick said there is a widespread misconception that unexploded ordnance becomes less dangerous over time. In a 2022 study, he tested samples of TNT and PETN, two of the most widely used high explosives, taken from World War II bombs and shells. However, it was found that there was no deterioration in the explosive properties.

Now he has tested the impact sensitivity of five samples of Amatol taken from unexploded World War II bombs and artillery shells found in Norway. The test involved dropping weights from various heights on small samples to see what would explode. All five samples were more sensitive to shock than expected with Amatol, and one sample was four times more sensitive.

Novick says this discovery will change the way he and his team deal with unexploded ordnance. For example, when clearing a dump, fewer volumes are transported at once. He now plans to find out why shock sensitivity has increased. “We think sensitive crystals or salts may have formed,” he says.

This may be the result of contaminants from the manufacturing process, or reactions with the metal case as the lining deteriorates, or simply due to aging.

Amatol is the name used to describe an explosive made from a mixture of TNT and ammonium nitrate. It was developed by Britain’s Royal Arsenal in 1915 when TNT was in short supply. As TNT production increased at the end of World War II, many countries stopped using Amatol, although it continued to be used in countries such as the Soviet Union. “Several types of Soviet-era ammunition currently in use in Ukraine are known to contain Amatol,” Novik said.

It’s impossible to say what percentage of the world’s unexploded ordnance contains amatol, he says. But five of the 20 bombs and shells he cut open for this study contained the substance, and so did most of the World War II unexploded ordnance he examined. has been found.

Accidents in which unexploded ordnance explodes also occur frequently. For example, in 2023, a World War II bomb exploded during disposal in Great Yarmouth, England. In 2004, new scientist A US ship that sank in the Thames Estuary was carrying 1,400 tonnes of high explosives and posed a serious threat to nearby towns, an unpublished risk assessment has revealed. A 2023 survey of the ship found plans to remove the mast could be dangerous and were postponed.