EXPLOSION AT CHERNOBYL

THE BIG BLAST: On April 26, 1986, at 1:23 AM, Chernobyl became the site of the world's worst nuclear power plant accident. Operators were shutting down one of the reactors for maintenance when the power suddenly surged and the reactor exploded. The blast blew the reactor apart and sent radioactive gases and particles as high as 3 miles into the atmosphere. Two plant workers were killed by the explosion. Later 29 others died from radiation exposure.

Within days, more than 120,000 people were evacuated from an 18-mile radius around the plant. As fires inside the reactor burned, helicopters dumped tons of lead, sand, and other minerals on the flames. Despite these efforts, the fires burned for 10 days after the blast, continuing to release radioactive pollutants into the air.

WHERE IT WENT: The explosion resulted in a huge cloud that soon split into two parts. One part of the cloud moved northwest toward Poland and Scandinavia, and then southwest across central Europe. The other part of the cloud moved east across Asia, over Japan and the North Pacific and eventually reached western North America. (The "Pollution Points" on page 400 track the movement of both parts of the cloud.) And as the reactor continued to burn, it released radiation that moved south and east of the plant. But scientists believe that, in most cases, the amounts of radiation deposited outside the then Soviet Union were relatively low.

EFFECTS OF THE EXPLOSION: The first few weeks following the Chernobyl blast were filled with confusion. Some European countries ordered the destruction of millions of dollars worth of contaminated produce, milk, and livestock. But in other nearby European countries, people were told that there was no danger and that it was safe to consume these products. Farmers suffered huge financial losses when countries in other parts of the world refused to import produce from Europe.

The explosion also strained relations between the Soviet Union and other nations. Many countries were angered by the Soviet Union's delay in reporting the accident (officials didn't announce it until April 29).

CHERNOBYL'S LEGACY: The damaged reactor at Chernobyl now stands entombed in thick layers of concrete and steel, while the other reactors at the plant are again producing energy. But the disaster is still taking its toll. Some scientists predict that within the next few decades, thousands of people who were exposed to the radiation could develop cancer.