Chornobyl remains at risk 40 years after the disaster

Four decades after Reactor 4 exploded at the Chornobyl nuclear power plant in northern Ukraine, the site of the world’s worst nuclear disaster is once again shadowed by danger.

At 01:23am on 26 April 1986, an explosion tore through the reactor during a failed safety test, blasting apart the roof and sending a vast cloud of radioactive material into the atmosphere.

Radiation spread west and north across Europe for days, while neighbouring Belarus absorbed the heaviest share of the fallout.

Soviet authorities waited 36 hours before evacuating the nearby town of Prypiat, home to many of the plant’s workers and their families.

That acknowledgement came two days after the explosion.

The aftermath of a Russian drone strike at the Chornobyl Nuclear Power Plant in February 2025

In the weeks that followed, about 30 first responders died after exposure to extreme radiation levels, while two people were killed in the blast itself.

In the months after the disaster, thousands of soldiers, miners and construction workers were sent in to contain and clean up the radioactive contamination.

Fallout left more than 2,500sq/km around the plant uninhabitable, prompting authorities to establish an exclusion zone that remains in force today.

More than 200,000 people were permanently displaced from their homes.

How many ultimately died because of radiation exposure is still not known, though estimates place the toll in the thousands.

Children born near the plant were found to have higher rates of thyroid cancer, along with increased incidences of birth defects.

Chornobyl was formally decommissioned in 2000, when Reactor 3, the last of the site’s four reactors still operating, was shut down.

Inside the New Safe Confinement, installed in 2016, which protects the remains of Reactor 4

Today, more than 2,000 workers are still engaged in the painstaking work of decommissioning the site, handling nuclear waste and dismantling infrastructure.

The effort is overseen by the Ukrainian government and is expected to take decades to finish safely.

That work, however, has been severely disrupted by Russia’s full-scale invasion.

Russian troops occupied the plant during the first five weeks of the war and held 300 staff members captive.

“It was an act of nuclear terrorism by the aggressor state of Russia. It is very sad that the international community reacted very weakly, or, one might say, did not react at all,” Oleksandr Hryhorash, the head of Chornobyl NPP’s operational control told Ukrinform, the state news service of Ukraine, earlier this week.

“No one could have foreseen that nuclear facilities would be seized and shelled,” he said.

Electrical power to the plant was cut on the first morning of the Russian occupation, forcing back-up diesel generators to keep critical systems running for the next six days.

Although Russian forces withdrew from the site in late March 2022, easing the immediate threat to the decommissioned plant, Chornobyl remains vulnerable because of continuing Russian drone activity in the area.

In February 2025, a Russian drone hit and pierced the New Safe Confinement (NSC), the steel structure that encloses Reactor 4 — the reactor destroyed in the 1986 explosion.

The strike ignited a fire in the NSC’s outer layer, but firefighters put it out before radioactive material could escape through the protective оболка.