The Chernobyl disaster was an accident.
Chernobyl disaster . The red glow observed during the Chernobyl accident was the expected color of luminescence for graphite at 700 ° C and not a large-scale graphite fire , as some have incorrectly assumed . '' The Chernobyl accident dominates the Energy accidents sub-category , of most disastrous nuclear power plant accident in history , both in terms of cost and casualties . 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 . The Chernobyl disaster ( Чорнобильська катастрофа , Chornobylʹsʹka katastrofa , Chernobyl accident ) , was considered the worst nuclear disaster in history .