The Chernobyl disaster was a fire at a Ukrainian nuclear reactor, releasing substantial radioactivity within and outside the region. The consequences to human and environmental health are still felt to this day.

The V.I. Lenin Memorial Chernobyl Nuclear Power Station was located in Ukraine, near the town of Pripyat, which had been built to house power station employees and their families. The power station was in a wooded, marshy area near the Ukraine-Belarus border, approximately 18 kilometers northwest of the city of Chernobyl and 100 km north of Kiev, the capital of Ukraine. The Chernobyl Nuclear Power Station included four nuclear reactors, each capable of producing one gigawatt of electric power. At the time of the accident, the four reactors produced about 10 percent of the electricity used in Ukraine.

Construction of the Chernobyl power station began in the 1970s. The first of the four reactors was commissioned in 1977, and Reactor No. 4 began producing power in 1983. When the accident occurred in 1986, two other nuclear reactors were under construction.

The Chernobyl Nuclear Accident

On Saturday, ​April 26, 1986, the operating crew planned to test whether the Reactor No. 4 turbines could produce enough energy to keep the coolant pumps running until the emergency diesel generator was activated in case of an external power loss. During the test, at 1:23:58 am local time, power surged unexpectedly, causing an explosion and driving temperatures in the reactor to more than 2,000 degrees Celsius—melting the fuel rods, igniting the reactor’s graphite covering, and releasing a cloud of radiation into the atmosphere.

The precise causes of the accident are still uncertain, but it is generally believed that the series of incidents that led to the explosion, fire, and nuclear meltdown at Chernobyl was caused by a combination of reactor design flaws and operator error.

Loss of Life and Illness

By mid-2005, fewer than 60 deaths could be linked directly to Chernobyl—mostly workers who were exposed to massive radiation during the accident or children who developed thyroid cancer.

Estimates of the eventual death toll from Chernobyl vary widely. A 2005 report by the Chernobyl Forum—eight U.N. organizations—estimated the accident eventually would cause about 4,000 deaths. Greenpeace places the figure at 93,000 deaths, based on information from the Belarus National Academy of Sciences.

The Belarus National Academy of Sciences estimates 270,000 people in the region around the accident site will develop cancer as a result of Chernobyl radiation and that 93,000 of those cases are likely to be fatal.

Another report by the Center for Independent Environmental Assessment of the Russian Academy of Sciences found a dramatic increase in mortality since 1990—60,000 deaths in Russia and an estimated 140,000 deaths in Ukraine and Belarus—probably due to Chernobyl radiation.

Psychological Effects of the Chernobyl Nuclear Accident

The biggest challenge facing communities still coping with the fallout of Chernobyl is the psychological damage to 5 million people in Belarus, Ukraine, and Russia.

"The psychological impact is now considered to be Chernobyl's biggest health consequence," said Louisa Vinton, of the UNDP. "People have been led to think of themselves as victims over the years, and are therefore more apt to take a passive approach toward their future rather than developing a system of self-sufficiency.” Exceptionally high levels of psychological stress have been reported from the regions around the abandoned nuclear power station.

Countries and Communities Affected

Seventy percent of the radioactive fallout from Chernobyl landed in Belarus, affecting more than 3,600 towns and villages, and 2.5 million people. The radiation-contaminated soil, which in turn contaminates crops that people rely on for food. Surface and ground waters were contaminated, and in turn plants and wildlife were (and still are) affected. Many regions in Russia, Belarus, and Ukraine are likely to be contaminated for decades.

Radioactive fallout carried by the wind was later found in sheep in the UK, on clothing worn by people throughout Europe, and in rain in the United States. Various animals and livestock have been mutated by this as well.

Chernobyl Status and Outlook

The Chernobyl accident cost the former Soviet Union hundreds of billions of dollars, and some observers believe it may have hastened the collapse of the Soviet government. After the accident, Soviet authorities resettled more than 350,000 people outside the worst areas, including all 50,000 people from nearby Pripyat, but millions of people continue to live in contaminated areas.

After the breakup of the Soviet Union, many projects intended to improve life in the region were abandoned, and young people began to move away to pursue careers and build new lives in other places. "In many villages, up to 60 percent of the population is made up of pensioners," said Vasily Nesterenko, director of the Belrad Radiation Safety and Protection Institute in Minsk. "In most of these villages, the number of people able to work is two or three times lower than normal."

After the accident, Reactor No. 4 was sealed, but the Ukranian government allowed the other three reactors to keep operating because the country needed the power they provided. Reactor No. 2 was shut down after a fire damaged it in 1991, and Reactor No. 1 was decommissioned in 1996. In November 2000, the Ukranian president shut down Reactor No. 3 in an official ceremony that finally closed the Chernobyl facility.

But Reactor No. 4, which was damaged in the 1986 explosion and fire, is still full of radioactive material encased inside a concrete barrier, called a sarcophagus, that is aging badly and needs to be replaced. Water leaking into the reactor carries radioactive material throughout the facility and threatens to seep into the groundwater.

The sarcophagus was designed to last about 30 years, and current designs would create a new shelter with a lifetime of 100 years. But radioactivity in the damaged reactor would need to be contained for 100,000 years to ensure safety. That is a challenge not only for today but for many generations to come.