Timeline of the Disaster and its Aftermath
The Chernobyl disaster unfolded over hours, days, and weeks, with each stage marked by confusion, heroism, and a slowly dawning realization of the event’s true scale.
April 25, 1986: Operators at Chernobyl’s Reactor 4 begin preparations for a safety test. The test is delayed, and the evening shift, unprepared for the complex procedure, takes over.
April 26, 1:23 AM: A sudden, catastrophic power surge causes two explosions that destroy the reactor core and the building that houses it. Two plant workers are killed instantly. Fires break out across the site, including a massive blaze on the roof of the adjacent reactor building.
April 26, 1:28 AM: The first firefighting units arrive. Unaware of the lethal radiation levels, they battle the fires with no specialized protective equipment. Many would later suffer from Acute Radiation Syndrome (ARS).
April 27, 2:00 PM: After more than 36 hours of exposure to severe fallout, the evacuation of Pripyat’s nearly 50,000 residents begins. Busing convoys arrive, and people are told to pack only essential documents and a small amount of food, as they would be returning in three days. They never did.
April 28: Radiation alarms are triggered at a nuclear power plant in Sweden, over 1,000 kilometers away. Faced with international inquiry, the Soviet Union finally admits that a major accident has occurred at Chernobyl.
Late April to May 10: A heroic and desperate effort to control the burning reactor core unfolds. Helicopter pilots fly through dense radioactive smoke to drop more than 5,000 tons of sand, lead, boron, and clay onto the exposed core to extinguish the graphite fire and absorb radiation.
May 1986: The Soviet government establishes a 30-kilometer (19-mile) radius Exclusion Zone around the plant. The evacuation expands to include all towns and villages within this area, eventually displacing over 115,000 people. This number would grow to over 350,000 in subsequent years as the contaminated zone was redefined.
June to November 1986: The frantic construction of the “Object Shelter,” a massive steel and concrete structure known as the Sarcophagus, begins. It is designed to entomb the destroyed reactor and contain its radioactive contents. This work is carried out by hundreds of thousands of conscripts and civilian workers who became known as “liquidators.”
December 2000: After years of international pressure and assistance, Ukraine shuts down Reactor 3, the last functioning reactor at the Chernobyl Nuclear Power Plant. The site officially ceases to produce electricity.
November 2016: The New Safe Confinement (NSC), a colossal arched structure, is slid into place over the aging and unstable Sarcophagus. This monumental engineering project marks a new phase in securing the site for the next century.
