General view of the empty city of Pripyat in the Chernobyl Exclusion Zone. Pripyat counted 50,000 inhabitants before its evacuation following the nuclear disaster. Chernobyl in November 2015. The Chernobyl disaster (also referred to as the Chernobyl accident or simply Chernobyl) was a catastrophic nuclear accident that occurred on 26 April 1986 at the Chernobyl Nuclear Power Plant in the town of Pripyat, 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 Chernobyl disaster was the worst nuclear power plant accident in history in terms of cost and casualties. Photo by Francois Pauletto/ABACAPRESS.COM