The Accident at Three Mile Island

On March 28, 1979, one of the reactors at Three Mile Island, a nuclear power plant near Harrisburg, Pennsylvania, overheated. A combination of human error and a string of technical failures triggered a partial meltdown of the plant’s radioactive core and the consequent leakage of radiation into the environment. In the dramatic days following the accident, engineers, scientists and mechanics worked to minimize further release of radiation and to prevent a total meltdown of the core. Meanwhile, state and federal government officials hurriedly tried to come up with emergency response measures. Two days after the accident, Governor Richard Thornburgh advised preschool children and pregnant women within five miles of the plant to evacuate the area. Residents within a ten-mile radius were asked to stay at home, turn off their air-conditioners, and close their windows. Confused and frightened by conflicting information and sensationalist media reports, more than 100,000 people fled the area.

Twelve days after the accident, the Governor declared the situation under control. According to officials, “no significant amount” of radioactive iodine and cesium had leaked into the environment; a considerable amount of radioactive noble gases, however, had been released into the air.(1) An extensive clean up of the highly contaminated plant took more than a decade. The radioactive debris and the melted core were shipped to Washington State and Idaho. Three independent government commissions investigated the accident, and several public health studies were conducted. Most studies found no increase in cancer mortality rates of the population living within a five-mile zone of the plant, though an epidemiological study published in 1997 concluded that cancer rates among the population downwind of the plant have increased since 1979. The debate over the medical effects of the TMI accident continues.(2)

The TMI partial meltdown, which was the worst accident at an American commercial nuclear power plant, both altered nuclear regulation policies in the United States and shook the public's confidence in nuclear technology.

Echo has developed an online survey, which invites people to share their thoughts about the TMI crisis. We aim to collect entries from a broad spectrum of people, ranging from residents who lived near the plant to people who lived in a different part of the country (or in another country) and followed the events through the media. Our aim is to build a free and public archive that serves as a resource for activists and scholars alike.

(1)The total radioactivity released during the accident was 2.4 million curies. See: Thomas M. Gerusky. "Three Mile Island: Assessment of Radiation Exposures and Environmental Contamination." In: Thomas H. Moss and David L. Sills: The Three Mile Island Nuclear Accident: Lessons and Implications. New York: The New York Academy of Sciences,1981, p. 57.

(2)For a discussion of the epidemiological studies see: Steve Wing a.o. "A Reevaluation of Cancer Incidence Near the Three Mile Island Nuclear Plant: The Collision of Evidence and Assumptions," Environmental Health Perspectives 105:1 (Jan. 1997): 52-57. The authors of the study that Wing a.o. contest defend their findings in the same issue of EHP. Available online at: This first study was printed in: M. Hatch a.o. "Cancer Rates after the Three Mile Island Nuclear Accident and Proximity of Residence to the Plant." American Journal of Public Health 81 (1991): 719-724. See also a recent study by the University of Pittsburgh: UPMC Health System. Press Release: No Apparent Increase in Cancer Deaths Among Three Mile Island Residents, April 28, 2000:

Sources: Nuclear Accident and Recovery at Three Mile Island. A Special Investigation. Report to the United States Senate (Subcommittee on Nuclear Regulation for the Senate Committee on Environment and Public Works), Washington, D.C. June 1980.
-Bill Keisling, Three Mile Island: Turning Point. Seattle: Veritas Books, Inc., 1980.
-Raymond L. Goldsteen and John K. Schorr. Demanding Democracy After Three Mile Island. Gainesville: University of Florida Press, 1991.
-Thomas H. Moss and David L. Sills. The Three Mile Island Accident: Lessons and Implications (Annals of the New York Academy of Sciences, vol. 365). New York: The New York Academy of Sciences, 1981.
-David L. Sills/C. P. Wolf and Vivien B. Shelanski (eds.), Accident at Three Mile Island: The Human Dimensions. Boulder, Colorado: Westview Press, 1982.
-Peter S. Houts/Paul D. Cleary/The-Weih Hu. The Three Mile Island Crisis: Psychological, Social, and Economic Impacts on the Surrounding Population (The Pennsylvania State University Studies, No. 49). University Park and London: The Pennsylvania State University Press, 1988.
Thanks to Ed Lyman, Linda Shopes, Kelly Jordan and the EFMR Monitoring Group for help, suggestions and criticisms. None of them are responsible for mistakes or misrepresentations on this website.

Last updated August 5, 2004