Chernobyl disaster – Wikipedia

The Chernobyl disaster was a nuclear accident that occurred on 26 April 1986 at the No. 4 nuclear reactor in the Chernobyl Nuclear Power Plant, near the city of Pripyat in the north of the Ukrainian SSR. It is one of only two nuclear energy disasters rated as INES 7, the maximum severity classification.

: https://en.wikipedia.org/wiki/Chernobyl_disaster