Sometimes mankind has to face nuclear accidents and eliminate the adverse consequences of such disasters. The Chernobyl nuclear power plant accident occurred on April 26, 1986. It was the largest nuclear energy disaster in history. The explosion took place in the fourth block of the Chernobyl power plant. Radioactivity started to radiate out of the destroyed reactor of the power plant, which contaminated both the near and far environment. During the first three months after the disaster, 31 people died, 134 people died of acute radiation syndrome, and in the next 15 years 60 to 80 people died from radiation.

The accident at the Fukushima nuclear power plant in Japan, which occurred on March 11, 2011, is recognized the second most disastrous in the world. Following a major earthquake, a 15-metre tsunami disabled the power supply and cooling of three Fukushima Daiichi reactors. This year, the financial damage, including the cost of liquidation of the consequences, is estimated at $189 billion.

The Kyshtym disaster was a radiation contamination disaster, which happened on September 29, 1957, in Mayak, a nuclear plant in Russia. Due to the failure of the cooling system, there was a burst of the tank containing about 70–80 tons of liquid radioactive waste. Thousands of square kilometers of territory were contaminated.

The worst nuclear disaster in Great Britain's history occurred on October 10, 1957, in Windscale. The core of Unit 1's reactor caught fire, releasing substantial amounts of radioactive contamination into the surrounding area.

The fifth most disastrous nuclear accident is Three Mile Island accident, US, which occurred on March 28, 1979. Small amounts of radioactive gases and radioactive iodine were released into the environment. Luckily, epidemiology studies have not linked a single cancer with the accident.

The sixth place goes to the SL-1 accident. On January 3, 1961, a USA army experimental nuclear power reactor underwent a steam explosion and meltdown killing its three operators. The cause of this was the improper removal of the control rod, responsible for absorbing neutrons in the reactor core.

The seventh place among most catastrophic nuclear disasters belongs to the Saint-Laurent accident, France. On the March 24, 1969, 50 kg of uranium in one of the gas cooled reactors began to melt. Fortunately, the leakage of radiation was insignificant, and no one was hurt outside the nuclear power plant.