Chernobyl Nuclear Accident

Historical Importance of Chernobyl Nuclear Accident: The large environmental disaster caused by the meltdown at the nuclear power plant near Chernobyl, Ukraine, dramatically changed the world's opinion about using nuclear reaction for power.

Dates: April 26, 1986

Also Known As: Chernobyl Nuclear Disaster

Overview of Chernobyl: The Chernobyl nuclear power plant was built in the wooded marshlands of northern Ukraine, approximately 80 miles north of Kiev. It's first reactor went online in 1977, the second in 1978, third in 1981, and fourth in 1983; two more were planned for construction. A small town, Pripyat, was also built near the Chernobyl nuclear power plant to house the workers and their families.

Routine Maintenance and a Test on Reactor Four

On April 25, 1986, reactor four was going to be shut down for some routine maintenance. During the shutdown, technicians were also going to run a test. The test was to determine whether, in case of a power outage, the turbines could produce enough energy to keep the cooling system running until the backup generators came online.

The shutdown and test began at 1 a.m. on April 25th. To get accurate results from the test, the operators turned off several of the safety systems, which turned out to be a disastrous decision. In the middle of the test, the shutdown had to be delayed nine hours because of a high demand for power in Kiev. The shutdown and test continued again at 11:10 p.m. on the night of April 25th.

A Major Problem

Just after 1 a.m. on April 26th, the reactor's power dropped suddenly, causing a potentially dangerous situation. The operators tried to compensate for the low power but the reactor went out of control. If the safety systems had remained on, they would have fixed the problem; however, they were not. The reactor exploded at 1:23 a.m.

The World Discovers the Meltdown

The world discovered the accident two days later, on April 28th, when operators of the Swedish Forsmark nuclear power plant in Stockholm registered unusually high radiation levels near their plant. When other plants around Europe began to register similar high radiation readings, they contacted the Soviet Union to find out what had happened. The Soviets denied any knowledge about a nuclear disaster until 9 p.m. on April 28th, when they announced to the world that one of the reactors had been "damaged."

Attempts to Clean Up

While trying to keep the nuclear disaster a secret, the Soviets were also trying to clean it up. At first they poured water on the many fires, then they tried to put them out with sand and lead and then nitrogen. It took nearly two weeks to put the fires out. Citizens in the nearby towns were told to stay indoors. Pripyat was evacuated on April 27th, the day after the disaster had begun; the town of Chernobyl wasn't evacuated until May 2, six days after the explosion.

Physical clean-up of the area continued. Contaminated topsoil was placed into sealed barrels and radiated water contained. Soviet engineers also encased the remains of the fourth reactor in a large, concrete sarcophagus to prevent additional radiation leakage. The sarcophagus, constructed quickly and in dangerous conditions, had already begun to crumble by 1997. An international consortium has begun plans to create a containment unit that will be placed over the current sarcophagus. It is expected to be completed in 2013.

Death Toll

It is estimated that the radiation from the Chernobyl disaster was 100 times more powerful than the atomic bombs dropped on Hiroshima and Nagasaki. Thirty-one people died shortly after the explosion, but thousands more will die from the long-term effects of radiation.