A 500 million euro hole in the roof of Chernobyl

It was two in the morning when Oleksandr Titarchuk was woken up by his phone. Within minutes he was in his car rushing to his workplace - the Chernobyl nuclear power plant.

When Titarchuk, the plant's chief engineer, arrived that morning a little over a year ago, he found firefighters and rescue teams already on the scene.

Towering above them was a huge steel structure covering the remains of the world's worst nuclear disaster. All Titarchuk could think about was the urgent message that woke him up: the structure had been hit by an attack drone.

The explosion tore through the outer shell of the steel arch. Built less than a decade ago, the structure was meant to safely enclose the “sarcophagus” – a hastily erected concrete tomb erected in 1986 around reactor 4 after an explosion that sent a radioactive cloud over Europe.

Titarchuk is proud of his composure. He was relieved to see that no one was injured. But the situation was serious. The drone's impact tore a hole in the north side of the steel arch, where fire was burning and smoke was rising.

Hour after hour, the fire spread through the space between the inner and outer layers of the arch, which was designed to provide a hermetic seal. Four days after the impact, it was completely engulfed in flames.

Worse, the fire spread deep into the inner membrane made of polymers and other materials - wrapped around the entire arch - which firefighters could not reach.

There was only one way to put out the fire, and that was to drill more holes into the structure. In total, more than 300 holes were drilled as firefighters attempted to put out the flames, according to technical staff at Chernobyl.

Several hundred people worked in shifts, climbing to great heights in winter temperatures that dropped below minus 10 degrees. Each of them carried a dosimeter to monitor radiation levels; when they exceeded the permissible limit, they took turns.

Drones with thermal cameras, which helped monitor the fire, showed that it was smoldering until March 3 - a full 17 days after the drone hit.

The arch was built to prevent the damaged nuclear facility from endangering the world again for at least another hundred years. Now it is compromised, exposed to the elements and susceptible to corrosion.

Inside the now-damaged arch, large enough to hold the Statue of Liberty, is an unstable concrete “sarcophagus,” containing hundreds of tons of nuclear fuel and vast quantities of radioactive dust, including uranium and transuranic elements. Without significant repairs to the arch, officials warn, corrosion will begin in less than four years.

"The real lesson of Chernobyl was never just about engineering or physics - but about the collective moral responsibility of our species to protect the world from its own inventions," Tarakanov said. If we allow a man-made war to break through a man-made protective shield, we are admitting that while we have learned to master the atom, we have not learned to master ourselves, Tarakanov said.

"If the (concrete) shelter collapses, a radioactive cloud will rise," says the plant's general director, Serhiy Tarakanov.

The cash-strapped Ukrainian government has taken the first steps to repair the hole made by the drone. However, the European Bank for Reconstruction and Development estimates that around 500 million euros will be needed to make the site safe again.

The appeal for donations, as well as the 40th anniversary of the 1986 disaster, point to the ongoing danger at one of the world's most vulnerable nuclear sites.

All of this comes at a time of deep international divisions. War rages in Ukraine, including near its nuclear facilities. The Middle East is in flames. And in the White House is Donald Trump, a vocal skeptic of multilateral projects.

“As 1986 taught us, radiation knows no borders,” Tarakanov says. “The wind will blow these transuranic elements across Europe.”

“This is not a ‘Ukrainian problem,’” he added. “It is a continental threat that is being ignored.”

"New Safeguard": How the Arc Works

When the “New Safety Shell” (NSC) – the official name for the €1,5 billion arch – was built in 2019, it was designed with multiple layers to protect the “sarcophagus” below, and to be resistant to moisture, radiation, heat, and even a category three tornado.

It is intended to buy Ukraine, and the world, time to find a permanent solution for the remains of the reactor located beneath it, as well as for the radioactive material in its surroundings.

Built in two sections, the arch was erected using rails and hydraulic cranes. The NSC designers expected it to last a century. What international donors did not foresee was a major war - let alone a drone attack in February 2025.

Chernobyl is located in northern Ukraine, near the border with Belarus, along an air corridor frequently used by Russian missiles and drones, including those aimed at Kiev. Ukrainian officials say last year’s attack was deliberate and carried out by an Iranian-designed “Shahed” drone. Ukrainian President Volodymyr Zelensky said the drone flew at an extremely low altitude of 85 meters, likely to avoid radar detection.

The site became an active military zone in the first weeks after the Russian invasion began in 2022. Soldiers occupied the facility and camped in the exclusion zone, kicking up radioactive dust as they moved through the highly contaminated “Red Forest” surrounding the power plant.

The metal frame of the arch is 108 meters high and weighs almost three times as much as the Eiffel Tower. Among the remains of Unit 4 are the damaged reactor and about 5.000 tons of sand, lead and boric acid, dropped by helicopter after the disaster. The European Bank for Reconstruction and Development says that 190 tons of uranium dioxide fuel still remain in the unit. The lower parts of the reactor contain “masses of lava-like fuel”, with molten steel and concrete in various places.

Damage - and what needs to be fixed

Last year's drone strike did not cause radiation to leak into the atmosphere, officials say. However, damage to the outer shell of the arch and holes drilled by emergency workers have disrupted the NSC's ventilation system.

Without repairs to the ventilation system, “corrosion will start to eat away” the arc by the end of this decade, said Balthazar Lindauer, head of the nuclear safety department at the European Bank for Reconstruction and Development.

Nuclear experts say the NSC has lost several key functions, including the ability to contain radioactive substances and provide a controlled environment for dismantling the “sarcophagus” – the main reason for its construction. “Without a sealed envelope, the whole system collapses,” said the plant’s director, Tarakanov. “Now there is an open connection between the inside and the outside world. This means we can no longer maintain the humidity within the required limits.”

The Chernobyl administration completed emergency repairs to the NSC in early October, covering the main damage with a protective shield before the onset of winter rains and snow.

But officials admit that the metal sheet is practically only there to keep water out. Simon Evans, a nuclear safety expert at the European Bank for Reconstruction and Development who managed the fund for the NSC construction, describes it as “a prettier tarpaulin.”

The second phase, Tarakanov said, involves temporary repairs worth between five and ten million euros, for which Ukraine is raising funds from donors. He said the bulk of the work - sealing all minor damage and restoring part of the membrane - should be completed this year.

The third phase aims to fully restore the functions of the NSC, which, as Tarakanov said, is “an extremely demanding task,” because the burned membrane was embedded in a so-called “sandwich” structure.

“Given the intense radiation fields directly above the destroyed reactor, this poses a huge technical challenge,” says Tarakanov.

The danger from Chernobyl

The Chernobyl “sarcophagus” was built in about 200 days in 1986, under extremely difficult conditions. The enormous levels of radiation made it impossible to follow standard building codes, and the structure was never completely stable. Plant officials warn that a nearby rocket strike could cause it to collapse, sending radioactive dust into the atmosphere through a leaky arch.

Thousands of people were mobilized from across the then Soviet Union to clear the debris after the explosion and seal off Reactor 4. While cleaning the roof, they wore lead aprons and respirators and worked under strict time limits to reduce exposure to gamma radiation, according to Adam Higginbotham in his book Midnight in Chernobyl. The “shelter facility” was designed to last 20 years, but it has been standing for 40.

At the time of the drone attack, officials were preparing a plan for “early dismantling” of the unstable parts of the sarcophagus. However, after the NSC was damaged, dismantling of the remains of the facility was suspended.

“You can’t continue until you have the necessary level of containment,” says International Atomic Energy Agency Director General Rafael Mariano Grossi. “The structure of the building is not compromised,” Grossi said. “But all the supporting systems are compromised — and the level of containment of radioactive materials is compromised.”

Ukrainian nuclear officials warn that combat operations could trigger another incident.

“Almost every day and every night we witness enemy missiles and drones flying over the Chernobyl zone,” Tarakanov says. Drones and missiles can malfunction, be “blinded by electronic jamming systems or simply go off course,” he adds, while there is also the possibility of a deliberate strike: “The consequences of that would be catastrophic.”

“The impact of a rocket or a heavy drone near the arch creates a seismic shock,” he says. “No engineer in the world can guarantee that the shelter won’t collapse under such a quake.”

The site also houses the world's largest storage facility for spent nuclear fuel, as well as "huge quantities of liquid radioactive waste," he added. "An attack on any of these facilities - intentional or accidental - could cause a nuclear catastrophe on a global scale."

Ukraine has also called, with limited success, for greater international pressure on Russia over the war it is waging near nuclear facilities.

In May 2023, Grossi told the UN Security Council that both sides should respect five principles to ensure the safety of the Zaporozhye nuclear power plant, which Russia controls and operates.

“These principles boil down to two things,” says Grossi. “Don't shoot at a nuclear power plant, and don't turn a nuclear power plant into a military base for projecting force toward the other side.” However, no binding resolution has been adopted.

“The real lesson of Chernobyl was never just about engineering or physics – but about the collective moral responsibility of our species to protect the world from its own inventions,” says Tarakanov. “If we allow a man-made war to break through a man-made protective shield, we are admitting that while we have learned to master the atom, we have not learned to master ourselves.”

Funding appeal

The International Chernobyl Cooperation Fund, which coordinates work on nuclear safety, protection and decommissioning in the Chernobyl Exclusion Zone, has more than 70 million euros at its disposal, according to the EBRD. However, Arvid Tirkner, the bank’s director for Ukraine and Moldova, estimates that the project’s costs will “exceed 500 million euros.”

Although the arc prevents the spread of contaminated dust into the surrounding area, it does not block gamma radiation, which reaches anyone working above it.

“At the top of the arc, you would receive the maximum annual dose (of 20 millisieverts) in just 11 hours,” Evans says. “That adds complexity to the job and raises the cost.”

EBRD officials describe the international support to Chernobyl so far as “the largest global cooperation on nuclear safety,” but say it has been put in “fundamental jeopardy” after the Russian drone attack.

In a sign of how much circumstances have changed since the port was built in 2019, Moscow was among its initial donors. The countries, Evans says, “recognized the need to support Ukraine… and agreed to provide funding for a long-term solution.” He hopes “the international community will come together again.”

Prepared by: NB