The drone, which was armed with a warhead, hit the outer shell that covers the nuclear power plant, which partially melted down in 1986 in one of the world’s most infamous disasters. Ukrainian president Volodymyr Zelensky blamed Russia for the attack, but the Kremlin has denied responsibility.
The shell – called the New Safe Confinement or NSC – was completed in 2016, after a six-year build. The 10-metre-thick steel construction weighs 25,000 tonnes and can withstand temperatures from -43 to 45ºC, as well as category-three tornado wind speeds.
Fear of corrosion lingered in the minds of those designing the NSC, something engineers counteract by passing warm air between its multiple steel and concrete layers, while dehumidifiers ensure humidity never goes above 40%.
During planning for the dome that entombs Chernobyl, the goal was to protect against the worst natural disasters. But its builders did not expect attacks from warheads dropped by drones, as appears to have happened this month.
“The dome was built many years before drone attacks were a risk that anyone took seriously, which may raise questions about whether it has any specific vulnerabilities to this kind of weapon,” says Arthur Holland Michel, a research partner at the Peace Research Institute in Oslo.
“That being said, drones generally carry a small explosive payload, so one would expect – and indeed hope – that it would take a lot more than a drone attack to compromise the structure.”
The attack did puncture the structure, suggesting that the strike’s payload exerted a pressure greater than the 36,000 pounds per square inch (psi) the steel outer casing was designed to withstand.
While the damage will be frustrating for the plant’s operators, it did not breach safety limits or cause any issues that could release radioactive materials into the atmosphere. “The protective structure is strong and reliable, though it has been damaged,” Oleksandr Kharchenko, director of the Kyiv-based Centre for Research on Energy and Clean Air, told the Associated Press.
The attack on the nuclear power plant is a significant moment because it changes the calculus engineers have to consider when they are developing such safety systems going forward. Nuclear plants had been considered beyond the pale, even in war.
Thankfully, the engineering industry has developed materials that can help, with one of the main lines of defence likely to be material hardening. Defence research has developed materials that can resist ballistic impacts, including MIL-A-46100, a steel alloy that is tempered at high temperatures and engineered to be significantly tougher than the steel encasing the current NSC. MIL-A-46100 has a yield strength of 205,000 psi and a significant impact toughness.
It is also possible that, if the protective dome over Chernobyl were being built today, it would not be made from steel in the first place. Instead, more military-grade metals such as tungsten, which is well known for its hardness and density, might be used – though steel was likely chosen as the original material for the NSC because of its resistance to corrosion.
“The issue isn’t drones as such; they’re just a delivery system,” says Lynette Nusbacher, a military historian and former senior lecturer in war studies at the Royal Military Academy Sandhurst. “The Russians can use – as they’ve shown – theatre ballistic missiles with conventional high-explosive warheads.”
Nusbacher points out that the issue will be preying on the mind of Ukrainian authorities. “If you hammer the thing with enough ordnance you’ll blow a hole in it, and once you do that you can make the hole bigger,” she says. “The action of conventional explosives in doing this will put a lot of radioactive dust into the atmosphere, and that’s the threat in the first instance.”
The issue is not just a concern for Ukraine. While the drone attack did not cause nuclear leakage, as far as authorities can see now, it does open up the potential for a horrifying new era of warfare. “You’re effectively turning the whole enclosed facility into a big dirty bomb,” says Nusbacher. Engineers have to figure out how to prevent that from happening.
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