<human>:  When did the Chernobyl disaster happen?
<bot>: The Chernobyl disaster happened on 26 April 1986. It was a nuclear reactor accident that took place in the Soviet Union. The reactor had been damaged by a series of explosions and the core was exposed to the atmosphere. A large amount of radioactive material was released into the atmosphere, and the accident resulted in the deaths of 31 people directly, and thousands more indirectly.