The structure at Chernobyl that was hit on Friday is a huge arching shelter covering what remains of the crippled reactor. The meltdown spewed radiation into the atmosphere and contaminated an 18-mile zone around the plant that residents were forced to leave.
The protective structure, which resembles an aircraft hangar, was completed in 2016. It covers another structure known as the sarcophagus that was built immediately after the disaster.
The exploding drone breached the outer shield but did not damage the older, interior containment structure, Leontiy Derkach, a radiological engineer at the site, said in a telephone interview.
The explosion sprayed shrapnel into the space between the two structures, damaging both, he said, but did not spread radioactive materials. Emergency crews responded at about 3 a.m., he said, as the fire still burned.
The first people to approach the site were workers with radiation meters, to ascertain if radiation was leaking, he said. “We are not kamikazes to immediately go into the danger zone,” he said.
Air samples determined no radiation was leaking, Mr. Derkach said. Ukrainian military chemists and radiation specialists are still working at the site to gain a fuller picture of the damage. By around noon, he said, crews had not yet entered the outer containment structure for a closer view.
The drone, he said, had hit about 60 yards from where protective plates covered highly radioactive debris from the 1986 accident. Had it hit at that location, he said, the exploding drone could have spread radiation at least inside the outer containment structure.
Emergency crews, Mr. Derkach said, were assessing how to repair the hole. “The Russians caused us great damage,” he said. “The whole world built this shelter and the Russians destroyed it in one second.”
Greenpeace, the conservation group, issued a statement on the strike on the Chernobyl plant, saying it was “a further escalation of the threat to Ukraine’s nuclear power plants and must be condemned and punished.”
Chernobyl was among the first locations targeted in Russia’s invasion of Ukraine in February 2022, as the Russian army captured and occupied the decommissioned plant and used the site as a base for attacks on Kyiv, to the south.
Radiation levels rose for several days, most likely from columns of heavy weaponry stirring dust. During the monthlong occupation of the site, Russian soldiers dug trenches in irradiated soil, and electrical power to a cooling pool for nuclear waste was briefly cut, raising alarms.
The International Atomic Energy Agency said that its staff members at the site of the former nuclear plant had heard the explosion overnight.
The strike on Chernobyl, about two hours north of Ukraine’s capital, Kyiv, and the recent increase in military activity around the Zaporizhzhia nuclear power plant in a Russian-occupied zone “underline persistent nuclear safety risks,” said Rafael Grossi, the agency’s director general.
Ivan Nechepurenko and Maria Varenikova contributed reporting.
