On This Day: Chernobyl Nuclear Power Plant Melts Down

In the early morning hours of April 26, 1986, workers at the Chernobyl Nuclear Power Plant ran a test on reactor No. 4 to check how long it could run without electrical power. When power generation fell to less than 1 percent of capacity, operators tried to compensate by manually removing the rods that slow and control the nuclear reaction.

The reactor reached the planned test power levels, but workers could not re-insert the control rods. The reaction accelerated, building pressure that blasted a containment lid off the reactor’s core. Air rushed in, setting off a second explosion.

The radiocative release of the blasts was about 400 times that of the atomic bomb dropped on Hiroshima. Radioactive plumes traveled all over Europe, but present-day Belarus and Ukraine bore the brunt.

Firefighters raced to the scene to prevent the fire spreading to the other reactors, exposing themselves to high levels of radiation. “These were the people who saved Europe,” said firefighter Viktor Birkun. “If they had not done what they did, the fire would have spread to Reactors 1, 2 and 3.”

The Soviet government refused to admit that a disaster had taken place at Chernobyl. It was not until a Swedish nuclear facility detected high levels of radiation did the news of Chernobyl became public and nearby town of Pripyat was evacuated.

“Naturally, we can regret, today, after the fact, that we did not grasp everything more quickly,” said Soviet leader Mikhail Gorbachev on the 20-year anniversary of the event, adding, “I confess that we were afraid of panic—you can imagine for yourselves the consequences of a terrible panic in a town of several million inhabitants.”

Though less than a hundred people are believed to have died directly from the disaster, it has caused suffering and long-term health problems for people within hundreds of miles of Chernobyl.

“The psychological effects have been devastating,” said physicist Mikhail Malko to National Geographic. “Many women feel they will give birth to unhealthy babies or babies with no future. Many people feel they will die from Chernobyl.”

The World Health Organization (WHO) conducted a three-year study, publishing the results in September 2005. It concluded that only 56 people died as a direct result of the Chernobyl disaster. There was an increase in the number of thyroid cancer cases, due to radioactive iodine being absorbed into grass used as cattle feed. The iodine was then passed to children through milk.

Greenpeace puts the total mortality rate from the Chernobyl disaster at more than 90,000. This number was based on one study, which included “high levels of speculation and general uncertainty.”

The International Atomic Energy Agency says the disaster led to “4,000 fatal radiation-induced cancers” in the 600,000 most highly exposed individuals, and “perhaps another 5,000 in more peripheral populations.”

The town of Pripyat remains abandoned, as its residents were forced to relocate to Slavutych, a city built to replace Pripyat. The area in a 30-kilomter radius around the plant is still radioactive and may be entered only through a checkpoint.

The lack of human development in the contaminated zone around the plant has beckoned wildlife back in, including a rare species of bear. While radioactivity has somewhat subsided, animals in the area are highly radioactive and unfit for human consumption. Sergey Gaschak, a radioecologist studying the area’s wildlife and plants, says, “animals don't seem to sense radiation and will occupy an area regardless.”

Georgia State University’s physics department has a diagram explaining the reactions that led to the explosion. Nuclear reactors produce an iodine isotope, I-135, which decays into Xenon-135. In a properly functioning reactor, the two isotopes are in balance.

In Chernobyl’s reactor No. 4, the level of xenon began to increase because the iodine was “near full-power equilibrium concentration to produce it and the neutron flux necessary to ‘burn it away’ was not present.”