April 1986 The Chernobyl Nuclear Reactor meltdown and fire occurred in the Soviet Union. At 1:23 am on April 26, 1986, a powerful explosion in Chernobyl's Reactor Number 4 blew aside a 1,000-metric-ton, two-foot-thick steel lid and blasted through the concrete containment wall around the reactor. The reactor burst into flames. Two men died in the first few moments of the explosion. Thirty others, mostly firemen, died in the months to follow. Massive quantities of radioactive material were released. The explosion sent a radioactive plume 1,500 meters in the air. Eastern Europe and Scandinavia detected radiation from Chernobyl the next day. Soviet authorities evacuated 135,000 people within 30 kilometers of Chernobyl. By the end of May, the authorities evacuated villages beyond the 30 kilometer radius. In response to the Chernobyl accident, the U.S. Department of Energy investigated and shut down the N-Reactor at its Hanford Site in Eastern Washington. N-Reactor was the only American production reactor remotely similar to the Chernobyl reactor. N-Reactor was never restarted.