[chris]

Reactor 4 at the Chernobyl nuclear plant was destroyed by a power surge at about 1:23 a.m. on April 26, 1986, during a safety test run ahead of a routine maintenance shutdown. Operators were trying to establish whether a slowing turbine could still supply enough power to run the cooling pumps through a station blackout.

The surge caused a steam explosion that blew the 1,000-ton roof off the reactor, followed by a second blast and a graphite fire that burned for days. At least 5 percent of the radioactive core was thrown out, and the fallout was later measured across much of Europe.

Two plant workers were killed that night. Another 28 died within weeks of acute radiation syndrome.

Pripyat, the town built for the plant's staff, was evacuated the following day, moving about 45,000 people. Some 350,000 were resettled in all.