Eric Schmieman worked for 15 years on the modern engineering equivalent of the Great Pyramid — building a giant protective shield for a damaged reactor at Chernobyl that would protect the world from further fallout from the worst ever nuclear disaster.
The steel shell, slid into place over Reactor No. 4 on railroad tracks in 2016, is the world’s largest movable structure. It is as tall as a football field and weighs almost 40,000 tons. More than 45 countries and organizations spent almost $1.7 billion building it.
“We did a lot of safety analysis, considering a lot of bad things that could happen,” said Mr. Schmieman, 78, a retired civil engineer from Washington state who was a senior technical adviser on the project. “We considered earthquakes, tornadoes, heavy winds, 100-year snowfalls, all kinds of things. We didn’t consider acts of war.”
On Feb. 14, a drone with a high-explosive warhead that likely cost as little as $20,000 to produce punched a hole in the steel shell. Ukrainian officials said the Russians deliberately targeted the structure with a Shahed 136 drone. The Kremlin has denied responsibility.
While the initial fire was quickly put out, a waterproof membrane inside the insulation of the arch burned and smoldered for almost three weeks, said Artem Siryi, the head of the operations department for the structure, called the New Safe Confinement. Emergency workers in mountain-climbing equipment had to knock holes into the shield’s outer layer, hunting for the fire, and spray water inside a structure designed to stay dry to prevent corrosion, Ukrainian officials and international experts said.
On March 7, Ukraine declared the fire officially extinguished. But by that point, roughly half of the northern section of the shield had been damaged, Ukrainian officials said. The International Atomic Energy Agency said on March 13 that the fires and smoldering had caused “extensive damage, including to the northern side and to a lesser extent to the southern side of its roof,” according to an evaluation that Ukraine shared with the agency.
Radiation levels outside Chernobyl are still normal, the I.A.E.A. and Ukrainian nuclear regulators say. But it is unclear how the shield will be fixed, how much it will cost and how long it will take.
Repairs could take years, nuclear experts warn. That could delay a plan to dismantle the damaged reactor and safely dispose of the radioactive waste that was supposed to begin over the next five years. And there are risks that the steel shell starts corroding — or that the temporary “sarcophagus” Soviet engineers built around the reactor almost 40 years ago, which still sits within the shell, deteriorates further.
“The reason the international community spent so much money and time building this structure is because they know the scale of the threat radiologically inside,” said Shaun Burnie, a nuclear specialist at Greenpeace who visited the damaged reactor at Chernobyl after the drone attack.
“It’s an enormous intellectual achievement to build something that could protect Europe, Ukraine and the world from what’s inside,” he said. “And now the Russians have basically blown a hole in it, both physically and metaphorically.”
On Thursday, Greenpeace released a report saying the drone attack severely compromised plans for the damaged reactor and that the shell was no longer functioning as designed. Jan Vande Putte, a nuclear specialist at Greenpeace Ukraine, said the entire shell might have to be removed, dismantled and replaced — a view echoed by Mr. Schmieman and Mr. Siryi. The I.A.E.A. said the shell’s confinement function had been compromised and that the structure needed “extensive repair efforts.”
Both Russia and Ukraine have targeted one another’s energy infrastructure since Moscow’s full-scale invasion in February 2022, but both have also stopped short of launching major strikes at nuclear power plants.
On Wednesday, as part of negotiations on a potential cease-fire, President Trump suggested that the United States take over Ukraine’s electrical and nuclear power sites, arguing that this would help protect them.
Drones continue to fly over Chernobyl almost every night, Mr. Siryi said in an interview. “Their motor noise has become a familiar sound,” he added. Many were likely heading toward Kyiv, the country’s capital.
For people of a certain age, the explosion at Chernobyl in 1986, after years of heightened fears of nuclear war between the Soviet Union and the United States, was the stuff of nightmares. It sent a plume of radioactive material into the air, caused a public health emergency across Europe and led many to question nuclear energy. The Soviets, who initially hid the extent of the disaster, hastily built the concrete-and-steel emergency “sarcophagus” to encase the damaged reactor. Authorities also set up a 1,000-square-mile “exclusion zone” where no one was allowed to live.
The explosion’s official death toll was 31. But many other people got sick or eventually died. Cancer rates, especially for thyroid cancer, increased in areas heavily exposed to radiation.
The sarcophagus, which has become increasingly unstable, was never meant to last. Figuring out how to replace it took decades.
The confinement structure at Chernobyl that Mr. Schmieman worked on was an engineering and construction feat, designed to protect the damaged reactor for 100 years. To minimize radiation exposure, the structure was built about one-third of a mile away from the damaged reactor, then moved into place. It is about 40 feet thick, with an outer and an inner shell that are both made of steel. The humidity level between the shells is kept below 40 percent to prevent corrosion.
The outer shell is the key to keeping out precipitation, Mr. Schmieman said. The inner shell is designed to keep the radioactive dust inside the structure, especially when the cranes already set up start taking apart the sarcophagus and the damaged reactor before safely disposing of the waste in smaller containers.
By the end of this year, specialists had aimed to finish the initial plan outlining the first dismantling stage. “Unfortunately, that’s no longer possible” because of the drone attack, Mr. Siryi said.
He said experts were evaluating how the shell could be fixed — and even if it could be. Workers would have to close the initial 540-square-foot hole from the drone. But they would also have to seal up the small holes created by workers trying to extinguish the fire. They would have to somehow repair the damaged membrane and insulation and any damaged internal structures. And they would have to reduce the humidity that resulted from hundreds of workers spraying high-powered hoses inside the structure.
Doing that where the confinement shell now sits is probably not possible, experts said, because workers would be exposed to high radiation levels from within. Moving the structure and then fixing it would also be challenging. What would protect the already unstable sarcophagus while that work was carried out?
“Full restoration of the facility is practically impossible,” Mr. Siryi said. “To bring it as close as possible to its original state — well, that would likely require hundreds of millions of dollars.”
Mr. Schmieman said repairing the structure, or building a new one, would be extremely costly. He suggested temporarily covering the holes — with something akin to duct tape — so the ventilation system inside could start reducing humidity. “Don’t immediately look for a quick, permanent solution for the large number of holes in the building, but look for a quick way to reduce corrosion,” he said.
One thing that might help, he said: drones. Largely because of the war, Ukraine has developed drone technology faster than almost any other country. Small drones — much smaller than the Shahed 136 that pierced the structure — could perhaps evaluate the damage inside the shell, and even help with fixing it.
Oleksandra Mykolyshyn contributed reporting.