It was meant to be a routine safety check. A procedure at the Chernobyl nuclear power plant in Ukraine on the evening of April 25 and early morning of April 26, 1986, should have passed without a hitch. But a combination of poor design and under-trained operators led to an unthinkable disaster. The plant went into meltdown, before exploding and setting surrounding buildings alight.
However, this being a nuclear plant, the most devastating consequence was not the explosion and resulting inferno. Rather, it was the spewing out of radioactive material into the atmosphere. The explosion killed two men at the plant. Another 28 operators and firemen died within a few months from the effects of acute radiation poisoning.
Not surprisingly, the radioactivity levels around the site were lethal. Exposure to radiation can be measured by roentgen units, with exposure to about 500 roentgens per hour for a period of five hours enough to kill an adult. Incredibly, in the aftermath of the explosion, the area around the power station was delivering an estimated 20,000 roentgens per hour.