Ukraine's nuclear ghosts were raised again on Friday after a drone armed with a warhead hit the protective outer shell of the plant at Chernobyl, the site of the world’s worst nuclear accident.

The strike, which Kyiv blamed on Moscow, did not breach the plant’s inner containment shell and radiation levels did not increase, according to the U.N. nuclear watchdog, the International Atomic Energy Agency.

Russia denied involvement, and accused Ukraine of waging a false flag attack. Their competing claims could not be independently verified.

What's at stake?

The timing is sensitive as the incident comes against the backdrop of the Munich Security Conference, a gathering of world leaders meant to hash out paths to ending the nearly three-year war.

Both Russia and Ukraine have traded accusations, claiming the other is trying to derail President Donald Trump's efforts to help broker a peace deal.

Rafael Mariano Grossi, the head of the U.N. watchdog, the IAEA, said Friday's incident was deeply concerning and underlines the persistent risks to nuclear safety during the ongoing war.

“There is no room for complacency, and the IAEA remains on high alert,” he said in a statement. “I once again call for maximum military restraint around Ukraine’s nuclear sites.”

How dangerous can it be?

Ukrainian President Volodymyr Zelenskyy said a Russian drone slammed into the shell covering the remains of Chernobyl's reactor No. 4 — the same one that exploded on April 26, 1986, spewing radioactive fallout over much of Europe.

The 2-billion euro ($2.1 billion) structure, built in 2019, enclosed the original concrete shelter that was built over what was left of the exploded reactor.

Made of metal and designed to prevent any radioactive release from the exploded reactor, the outer shell is meant to protect it from any external hazards.

Experts have said the drone didn't threaten the integrity of the original concrete shelter, which can withstand a much heavier impact.

Three other nuclear reactors at Chernobyl have been shut down long ago, but the plant houses spent fuel and contaminated equipment awaiting to be dismantled during a long decommissioning process.

Some parts of the Russia-captured Zaporizhzhia nuclear power plant, which is Europe’s biggest, have been repeatedly struck by drones — attacks Russia and Ukraine blamed on each other — but none have led to radioactive threats.

Still, a slew of attacks earlier this week prompted the cancellation of a planned rotation of IAEA monitors at the Zaporizhzhia plant.

Russian troops occupied Chernobyl in the opening weeks of the war, raising fears that they could cause damage and trigger a radioactive accident. Since the Russians' withdrawal in late March 2022, Ukraine has mounted a drive to install further protections at the defunct site, including anti-drone systems and anti-tank barriers.

What about other risks?

The nearly three years of fighting have seen repeated power cuts to the critical cooling system at Chernobyl, as well as at Ukraine's four active nuclear plants, causing fears that spent nuclear fuel could overheat.

The cuts often follow shelling or drone strikes on nearby power lines, disrupting supply.

Nuclear safety experts have told The Associated Press that internal radioactive decay continues for thousands of years inside fuel rods after they have been used to generate power, giving off heat. Because of this, the rods are put in cooling pools, where they are cooled by both water and an electric-powered heat exchange pump.

The Swedish Radiation Safety Authority and others estimate that a power outage at Chernobyl would not lead to a risky radiation incident for at least a couple of weeks. This is because the fuel storage ponds are very deep, and it would take a long time for the water inside them to boil down, even if the cooling pumps were to stop.

Still, a lack of electricity would blind the IAEA’s radiation monitoring systems, installed to boost security.

And even if experts say a drone or missile strike is unlikely to trigger a major radioactive release, at least not without giving authorities time to take action, a power shutoff or the deliberate targeting of nuclear plants during the war can still cause significant panic and undermine peace efforts.

News from © The Associated Press, 2025