April 26, 1986
The worst accident in the history of nuclear energy; it killed 30 people and spewed radioactive material over the Soviet Union and Europe. Two workers died immediately after the accident and another 28 died during the next four months. 106 workers suffered acute radiation sickness. The disaster started when workers were running experiments on the reactor. Safety mechanisms had been disabled to facilitate the tests. The tests eventually caused an explosion that blew the top off the reactor and spewed radioactive material into the atmosphere. Chernobyl would eventually be declared a tourist attraction (2011).