Nuclear Power Plant Accidents

The chance of a large release of radioactive iodine from the type of reactor used in the United States is much lower than the chance of a large release in countries that use reactors such as the one used at Chornobyl.

Chornobyl
Chornobyl is probably the most well-known nuclear incident in the world. On April 26, 1986, large quantities of radioiodine were released into the environment (50 percent of what was present in the reactor) and a large population was exposed. The plume from Chornobyl reached as high as 6 miles and led to the dispersal of radioactive material over portions of Ukraine, Belarus, and Russia. The first indication of health problems in the population exposed to fallout came 4 years after the accident when hospitals began reporting an increase in the numbers of children with thyroid carcinomas. By the year 2000, there were about 2,000 cases of thyroid cancer attributed to fallout from Chornobyl. Cases are still being discovered; therefore, the full consequences will not be known for decades.

Three Mile Island
On March 28, 1979, a nuclear accident occurred at the Three Mile Island Nuclear Power Station in south-central Pennsylvania. The accident began when the plant experienced a total loss of feed water and the main turbine shut down. The reactor core did not receive enough cooling water, so it experienced a melt down. As a result, about 40 percent of the radioiodine was released from the core into the reactor building, but only a small portion of it escaped to the environment. Potassium iodide was rushed to the area three days after the accident, but never needed to be distributed to the public. In a 20-year follow-up study of mortality data on residents living within a five-mile radius of Three Mile Island during the incident, researchers at the University of Pittsburgh's Graduate School of Public Health found no significant increase overall in deaths from cancer.