This nuclear accident, which occurred at Chornobyl Nuclear Power Plant (situated 120 km to the North of Kyiv, capital of Ukraine) in Ukrainian Soviet Socialist Republic (then part of the Soviet Union), considered to be the worst technological disaster in the history of mankind. 145 square km of the territory of Ukraine, Belarus and Russian Federation were irradiated, more than 5 mln. people suffered, 5 000 towns and villages of mentioned countries were polluted by radioactive nuclides.

Powerful emission of radioactive substances into environment took place after the explosion of the fourth nuclear reactor of Chornobyl Nuclear Power Plant and ruining of its protective cover. Chornobyl disaster seriously changed radioactive situation on vast territories in many European countries. Approximately 200 types of radioactive isotopes were moving at thousands kilometers distances and in May 1986 were observed in all the countries of Northern and Western Europe, in Pacific, Atlantic and Arctic oceans.

Chornobyl disaster showed how heavy nuclear accidents cause global results and influence vital interests of many countries. This nuclear accident still negatively effects development of the whole world at the same time raising concerns about the safety of nuclear power plants.