The Chernobyl nuclear power plant is the site of the world's worst nuclear accident.

When an explosion tore through Chernobyl's No. 4 reactor on April 26, 1986, more than 30 people were killed near Pripyat, Ukraine. Countless others have died from radiation symptoms since, according to the International Atomic Energy Agency and the World Health Organization.

The disaster sent a cloud of radioactive fallout over hundreds of thousands of square miles of Ukraine, Russia and Belarus. The radioactive effects of the explosion were about 400 times more potent than the bomb dropped on Hiroshima during World War II.

The disaster forced the evacuation of a 30-kilometer zone around the site. More than 100,000 people were evacuated from their homes.
The disaster forced the evacuation of a 30-kilometer zone around the site. More than 100,000 people were evacuated from their homes.
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A worker measures radiation levels at the power plant.
A worker measures radiation levels at the power plant.
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People are scanned for radioactivity before evacuating.
People are scanned for radioactivity before evacuating.
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Customs officials in Germany closely screen goods, cars and people coming in from Eastern Europe in May 1986. Radioactivity from the Chernobyl nuclear plant threatened to contaminate crops.
Customs officials in Germany closely screen goods, cars and people coming in from Eastern Europe in May 1986. Radioactivity from the Chernobyl nuclear plant threatened to contaminate crops.
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In Finland, milk is tested by authorities for effects of the radiation.
In Finland, milk is tested by authorities for effects of the radiation.
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A farmer in Sweden wears a protective suit as he sifts hay possibly contaminated by the radioactive cloud from Chernobyl in June 1986.
A farmer in Sweden wears a protective suit as he sifts hay possibly contaminated by the radioactive cloud from Chernobyl in June 1986.
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Construction crews build a containment wall around the damaged unit four reactor in August 1986.
Construction crews build a containment wall around the damaged unit four reactor in August 1986.
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A doll remains in an evacuated village in Belarus near Chernobyl. Millions of people were exposed to dangerous radiation levels, and <a target="_blank">estimates of the final death toll</a> from long-term health problems are as high as 200,000.
A doll remains in an evacuated village in Belarus near Chernobyl. Millions of people were exposed to dangerous radiation levels, and estimates of the final death toll from long-term health problems are as high as 200,000.
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