The Chernobyl disaster (also referred to as Chernobyl or the Chernobyl accident) was a catastrophic nuclear accident that occurred on 26 April 1986 at the Chernobyl Nuclear Power Plant in Ukraine (then officially the Ukrainian SSR), which was under the direct jurisdiction of the central authorities of the Soviet Union.
An explosion and fire released large quantities of radioactive particles into the atmosphere, which spread over much of the western USSR and Europe.
The 1986 Chernobyl and 2011 Fukushima nuclear power plant accidents both share the notorious distinction of attaining the highest accident rating on the International Atomic Energy Agency (IAEA) scale of nuclear accidents. No other reactor incident has ever received this Level 7 “major accident” designation in the history of nuclear power. Chernobyl and Fukushima earned it because both involved core meltdowns that released significant amounts of radioactivity to their surroundings.
Both of these accidents involved evacuation of hundreds of thousands of residents. Both still have people waiting to return to their homes. And both left a legacy of large-scale radioactive contamination of the environment that will persist for years to come, despite ongoing cleanup efforts.