Chernobyl disaster, accident in 1986 at the Chernobyl nuclear power station in the Soviet Union, the worst disaster in the history of nuclear power generation. The Chernobyl power station was situated at the settlement of Pryp’yat, 10 miles (16 km) northwest of the city of Chernobyl and 65 miles (104 km) north of Kyiv, Ukraine.



The disaster occurred on April 25–26, 1986, when technicians at reactor Unit 4 attempted a poorly designed experiment. Workers shut down the reactor’s power-regulating system and its emergency safety systems, and they withdrew most of the control rods from its core while allowing the reactor to continue running at 7 percent power. These mistakes were compounded by others, and at 1:23 AM on April 26 the chain reaction in the core went out of control. Several explosions triggered a large fireball and blew off the heavy steel and concrete lid of the reactor. This and the ensuing fire in the graphite reactor core released large amounts of radioactive material into the atmosphere, where it was carried great distances by air currents. A partial meltdown of the core also occurred.



Seven hundred thousand men were conscripted into the Chernobyl area to “liquidate” or “blot out” the released radiation from the Chernobyl Nuclear accident. The selfless efforts of these “liquidators”—miners, soldiers and firemen—are unparalleled in history. Sacrificing themselves, they prevented a potential nuclear explosion that could have killed hundreds of thousands across Europe.

Forty thousand died of these men died in once decade, and a further 70,000 are now disabled. Hailed as heroes in 1986.