¹⁾.

The faulty design of the reactor nr 4 combined with human error caused the disaster. That morning, the engineers put the plant into operation at very low power when the reactors are very unstable and did not take adequate precautions or coordinate their procedure with safety personnel. Suddenly there was an increase in heat, causing some of the pressure pipes with fuel to burst.

The Chernobyl explosion is one of only two nuclear power accidents classified as level 7 on the international scale of nuclear incidents. The second one is the Fukushima Daiichi nuclear disaster in Japan in 2011.