On the morning of April 26, 1986, a terrible explosion happened at the Chernobyl Nuclear Power Plant in northern Ukraine. Two workers died right away, and 28 more people died in the weeks that followed from radiation sickness. The blast sent out dangerous radiation that was 400 times stronger than the atomic bomb dropped on Hiroshima. It became the worst nuclear accident the world has ever seen.
Firefighters rushed to the scene and put out the fires in about six hours. But while they were fighting the flames, they created another serious problem. The water they used to fight the fire filled up the basement under the broken reactor. Under the damaged reactor, there were huge pools holding about 5 million gallons of water that normally helped cool the plant. Scientists worried that the hot melting core would burn through the concrete floor and hit the water, which would cause another huge steam explosion.
