The disaster at the fourth reactor of the Chernobyl Nuclear Power Plant occurred on April 26, 1986. More than 200,000 square kilometers of land, first and foremost, in Ukraine, Belarus and Russia, became contaminated. Around 115,000 people were evacuated from the 30-kilometer-wide affected zone.

The subsequent clean-up operation involved more than 600,000 people, about ten percent of whom died, and 165,000 became disabled. Thanks to the dedicated work of the disaster’s responders coming from all over the Soviet Union, a concrete structure covering the nuclear reactor No. 4 was installed - known as the Shelter Object - in November 1986. TASS remembers the world's worst nuclear disaster.