4Kyshtym - Level 6
On September 29th, 1957, a plutonium plant called Mayak was at the center of an accident that involved radiological contamination. The plant was known for nuclear weapons development as well as nuclear fuel processing in the midst of the Soviet Union's race to develop the atomic bomb. Unfortunately in this
rush, scientists, technicians, and other workers were careless with their safety precautions and standards of running a nuclear plant. A coolant tank broke, which led to eighty tons of coolant evaporating in the reactor heat, which then caused an ammonium nitrate explosion.
The blast had the force of one hundred tons of TNT and caused the 160-ton containment lid to blow off, which led to the spread of radioactive waste over 3500 kilometers. The area surrounding the plant was evacuated. The disaster has been named after the nearest major town, Kyshtym. On the INES scale, the Kyshtym disaster was rated at a Level 7, and today - even decades after the incident - it is considered to be one of the most contaminated places in the world.