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March 28

Three Mile Island Photo Credit: Clipart.com

Today in Science

Three Mile Island

The most serious nuclear accident in the United States occurred at Three Mile Island in Pennsylvania on this day in 1979.

It all began in the predawn hours when a pressure valve in the Unit-2 reactor at Three Mile Island malfunctioned. Contaminated water leaked into the building and the plant’s core began to overheat. Human mistakes compounded the problem, and by early morning the core had heated to just 1,000 degrees short of meltdown.

Two days later, a hydrogen gas bubble was discovered in the plant and nearby residents were encouraged to evacuate the area voluntarily. Low levels of radiation (less than amount of radiation a person faces during an average year) were released into the atmosphere, but to date no negative health impacts have been proven, although many studies have been conducted.

Although only employees at Three Mile Island were actually exposed to the radiation leak, public confidence in the nuclear industry suffered. For more than two decades following the accident, no new nuclear plants were ordered in the United States.

Check out the Science NetLinks collection The Atom and Nuclear Science for resources related to this topic. Our Verizon Foundation partner, the Smithsonian's History Explorer, also offers a high school lesson, Three Mile Island: The Inside Story, we recommend.


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