The Chernobyl disaster was an accident.
The Chernobyl disaster , also referred to as the Chernobyl accident , was a catastrophic nuclear accident . It is one of only two nuclear energy accidents classified as a level 7 event ( the maximum classification ) on the International Nuclear Event Scale , the other being the Fukushima Daiichi nuclear disaster in Japan in 2011 . During the accident , blast effects caused 2 deaths within the facility and later 29 firemen and employees died in the days-to-months afterward from acute radiation syndrome , with the potential for long-term cancers still being investigated . The accident motivated safety upgrades on all remaining Soviet-designed reactors in the RBMK ( Chernobyl No. 4 ) family , of which eleven continued to power electric grids as of 2013 .