Everyone is familiar with what happened on 26th April 1986 in reactor no.4 of Chernobyl Nuclear Plant near the city of Prypiat in Ukraine. A fatal accident occured during a safety test, the soviet reactor overheated and exploded with steam and radioactive elements, bursting into fire that was very hard to extinguish. I am not a scientist to explain how the reaction itself happened, but it outbursted with a deadly amout of radiation to the area near Chernobyl, and what's more - generated a radioactive cloud that was carried with the wind to other countries.
The day after the explosion the city of Prypiat was evacuated, it was inhabited by 50,000 people and the danger of radiation-related illnes was inevitable for them, just 3 kilometers from the reactor. Days later, an exclusion zone was set in the radius of 30km around the reactor, all the area was evacuated as well. Many people died directly in the explosion and during the cleanup of the catastrophy, the sources are contradicting in the amount of casualties varying from 30 people up to 16,000. It is truly hard to estimate, because thousands of people worked on the site for many years, securing the radioactive core of the nuclear plant. A few years ago the second, upgraded and super-safe and super-expensive sarcofagus was completed to asure maximum protection.