A Russian Shahed drone costing up to £75,000 is estimated to have inflicted tens of millions worth of damage to the site of the Chornobyl nuclear power plant, according to initial assessments and engineering experts.
The cost of a full fix is likely to be borne by western governments including the UK, because initial estimates are that a complete repair will cost more than the €25m available in a special international contingency fund.
The strike in mid February did not cause an immediate radiological risk, but it significantly damaged the €1.5bn containment structure built in 2017 to encase the destroyed reactor and is likely to take months if not years to completely repair.
The 110-metre high steel structure at Chornobyl was hit before 2am on 14 February, with sensors registering “something like a 6 to 7 magnitude earthquake,” according to Serhiy Bokov, the chief engineer on duty. “But we clearly understood it wasn’t that,” he said.
The attack – quickly concluded to be caused by a drone flying below at a level where it could not be detected by radar – punctured a 15-sq-metre hole in the outer roof. It also caused a particularly damaging, complex smouldering fire to the inner cladding of the structure that took over a fortnight to put out.
Consisting of two double arches and longer than two jumbo jets, the New Safe Confinement (NSC) was completed in 2017 to secure the hastily built, unstable Soviet-era sarcophagus, which covers over Chornobyl’s ill-fated reactor number four, the site of the world’s worst nuclear disaster in April 1986.
But the attack in February has rendered the sarcophagus open to the elements again, meaning that radioactive dust could get out and rainwater in, though the country’s environmental protection ministry says “the radiation background is currently within normal level and is under constant control”.
More significantly, the confinement structure is now more vulnerable in the longer term to rusting due to greater exposure to the elements and damage to the cladding. Two hundred small boreholes were also drilled into the structure in the effort to douse the cladding fire with water.
“Not fixing it is not an option,” said Eric Schmieman, an American engineer who worked on the design and build of the Chornobyl shelter for 15 years. A complete repair, he said would “cost a minimum of tens of millions of dollars and it could easily go to hundreds of millions” with the repairs taking “months to years,” he added.
Previously the shelter was intended to have a 100-year design life, allowing time to decommission the sarcophagus and nuclear waste below, but this is now in doubt without it being repaired, Schmieman added. Unlike other large metal structures, such as the Eiffel Tower, it was never possible to repaint it to prevent corrosion.
Below the sarcophagus lies a highly radioactive lava like mass, a mix of 200 tonnes of uranium from Chornobyl reactor number four and 5,000 tonnes of sand, lead and boric acid dropped on to the site by Soviet helicopters in the immediate aftermath of the disaster caused by the reactor going out of control.
A more detailed impact assessment is expected to be released in May, but the European Bank for Reconstruction and Development (EBRD), which funded the building of the shelter and is involved in the post bombing analysis, said “it is clear that the attack has caused significant damage”.
Other sources, familiar with the assessment exercise, told the Guardian that Schmieman’s estimates appeared correct. Though the EBRD holds €25m in funds to allow for emergency work, it said “significantly more funding is required” to tackle long-term decommissioning challenges thrown up by the incident.
A similar calculation was made by Ukraine’s environmental protection ministry. “It is likely that eliminating the consequences of Russian aggression will require more funds than are currently available in the International Cooperation Account for Chornobyl [the €25m EBRD fund],” said the ministry in a statement.
When the attack took place in February, Moscow blamed Ukraine. Russia’s foreign ministry spokesperson Maria Zakharova said the incident was a provocation “premeditated by the Kyiv regime”. However, Ukrainian prosecutors believe, having reviewed the drone’s trajectory from the north, that the attack was a “possibly intentional strike” by Russian forces and a potential war crime.
Shaun Burnie, a senior nuclear specialist with Greenpeace Ukraine, said he believed the attack would have “consequences lasting decades” and said that it had taken place because “Putin and the Russian state has conducted a deliberate form of nuclear terror against Ukraine and Europe” that has “gone unpunished”.
Further cash for repairs is most likely to come from western governments. Twenty-six countries contributed to the cost of the original shelter, including the US, UK, France, Germany and even Russia – of which the vast steel arch structure cost €1.5bn out of a total €2.1bn fund. Others also made donations, including Turkey.
Home to the remains of a nuclear reactor that went out of control and exploded in April 1986, the Chornobyl site is seven miles from the border with Russia’s ally Belarus. It was occupied by Russian soldiers trying to capture Kyiv in February 2022, and has remained on the frontline after Ukraine regained it that April.
Two people were killed in the 1986 disaster and 28 more died from radiation poisoning in its immediate aftermath, while 350,000 were evacuated from nearby towns. Two exclusion zones remain in place, one 18 miles (30km) from the plant, where small numbers of people live and work, and a second at 6 miles, including the ghostly, abandoned town of Pripyat, a relic from an unlamented Soviet era.
Tourists were allowed to visit until the Russian full-scale invasion, but now the site lies in a military border zone, complicating decontamination efforts. Russian soldiers dug up contaminated earth as they built trenches in sight of the reactor shelter, but Ukrainian soldiers shipped in sand to build their own fortifications.
Debris recovered from the site led Ukrainian prosecutors to conclude that the damage was done by a Shahed 136, an Iranian-designed delta wing drone that has become Russia’s most frequently used long-range attack weapon. Now made at sites in Russia, their $50,000 to $100,000 cost is far below the amount of damage caused.
Ukrainian officials say the first step will be to “develop and implement” a temporary seal to the hole in the shelter, though Schmieman cautions that “one thing that is not obvious from distance is that as you go up the shelter object, the radiation dose gets higher. So you have to train and cycle workers based on safe annual dose limits”.
A radical option for full repair, probably only viable in peacetime, would be to slip the shelter back along a set of rails on which it was originally built 180 metres away, to reduce the radiation exposure for the workers. But that would be a “multi-year project” Schmieman estimated.
Remotely operated cranes hanging from the confinement shelter were intended to dismantle the sarcophagus and nuclear material below, and the strike hit a point near the maintenance garage Bokov said. That too may impair the plans to gradually dismantle and decommission the disaster site below.
“We designed this building for lots of contingencies, but we didn’t design it for war,” Schmieman said. “Though most nuclear plants are designed to survive an aircraft falling on them, we didn’t do that because after the accident in 1986 there has been a no-fly zone at Chornobyl. We had thought nothing would be flying overhead.”
