Chernobyl Disaster
On April 25, 1986, a series of steam explosions followed by an open-air reactor core meltdown in the Chernobyl nuclear power plant released a significant amount of radioactive contamination into the atmosphere. It was later discovered that the accident was caused by a flawed reactor design that was operated by poorly-trained personnel.
The steam fire burned for nine days straight and 134 workers suffered radiation exposure. Of that number, 31 lost their lives over a period of several weeks. Others died from cancer that may have been linked to the radiation poisoning. In the end, the disaster setback the Soviet-led Russia $590 billion.