At 1:24 am on April 26, 1986, one of the four reactors of the Chernobyl nuclear power plant blew up. Located in the Ukraine 100 kilometers north of Kiev, Chernobyl was one of the largest nuclear power plants in Europe, producing a thousand megawatts of electricity, enough to light a medium-sized city. Before dawn on April 26, workers at the plant hurried to complete a series of tests of how the generator Reactor Number 4 performed during a power reduction, and took a foolish short-cut: they shut off all the safety systems. The reactors at Chernobyl were graphite reactors designed with a series of emergency systems that shut the reactors down at low power, because the core is unstable then-and the workers turned these emergency systems off. A power surge occurred during the test, and there was nothing to dampen it. Power zoomed to hundreds of times maximum, and a white-hot blast with the force of a ton of dynamite partially melted the fuel rods and heated a vast head of steam that blew the reactor apart.
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The explosion and heat sent up a plume five kilometers high, carrying several tons of uranium dioxide fuel and fission products. Over 100 megacuries of radioactivity were released, making it the largest nuclear accident ever reported. By way of comparison, the Three Mile Island accident in Pennsylvania in 1979 released 17 curies, millions of times less. This cloud traveled first northwest, then southeast, spreading the radioactivity in a band across central Europe from Scandinavia to Greece. Within a 30-kilometer radius of the reactor, at least one fifth of the population, some 24,000 people, received serious radiation doses (greater than 45 rem). Thirty-one individuals died as a direct result of radiation poisoning-most of them firefighters who succeeded in preventing the fire from spreading to nearby reactors.
For the western Independent States and the rest of Europe, the radiation dose was much lower but still significant. Data indicate that radiation outside of the immediate Chernobyl area will be expected to be responsible for from 5000 to 75,000 cancer deaths, because of the large numbers of people exposed.
