Clio Logo

Three Mile Island is a nuclear power plant located on the Susquehanna River in Harrisburg, Pennsylvania. The plant was made up of two linked facilities referred to as units, both of which came online in the mid 1970s. On March 28th 1979 Unit Two underwent a partial melt-down in what became the most famous nuclear accident to occur on US soil. Despite the impact of the radiation being difficult to discern, the accident has had a lasting impression on the perception of nuclear power in the U.S. It is active to this day.

  • President Jimmy Carter touring the plant, April 1, 1979.
  • Cleanup crew within the plant.
  • Three Mile Island as it functions today.


                On Mach 28th 1979 an accident occurred in Unit 2 of the Three Mile Island facility. The incident was induced by a valve blockage. This malfunction, usually easily fixed, was compounded by operator misunderstandings of the indicator lights. This caused the problem to be undetected for many hours, resulting in a partial meltdown in the core and causing the release of radioactive material. (Walker, 73-76). This resulted in a site emergency being declared and the governor of Pennsylvania and numerous agencies being alerted. Despite assurances that the incident was under control almost half of the 663,000 residents in the area chose to evacuate. (Cooke, 294)


                Response to the incident from state agencies was swift, locking off the plant and ensuring no more radioactive material was released. The EPA also began monitoring radiation levels within hours of the incident. The total amount of radiation released was minimal, being comparable to a chest X-ray for those in the surrounding area . Plant staff and government responders closed down Unit Two. It was later decommissioned and parts of it sent to other nuclear plants after being inspected for quality (Walker, 190-219).While there was panic at the time, some view the response as entirely appropriate and claim that such small-scale incidents are a necessary part of establishing new technology (Perrow, 45).

Lasting Impact

                Despite the relative mildness of the incident, it was cited by anti-nuclear activists throughout the U.S. as proof of the danger of nuclear power. As a result President Jimmy Carter, an ardent supporter of nuclear energy as an alternative to fossil fuels, was forced by political pressure to reduce his advocacy efforts (Luther, 154). Since the Three Mile Island incident the number of nuclear reactors built and maintained in the U.S. has declined considerably and public perception of nuclear power remains negative. Its impact on the perception and implementation of nuclear power policy is still being felt today.(

Cooke, Stephanie. In Mortal Hands: A Cautionary History of the Nuclear Age. Collingwood AUS: Black Inc. Press, 2009. This book by journalist Stephanie Cooke examines the use of nuclear power in the modern world, with special focus paid as to why nuclear power failed to develop in the way that many predicted and hoped. She specifically cites the problem of nuclear waste along with general public fears of nuclear power compared to fossil fuels or other alternatives. Luther, J. Carter "Political Fallout from Three Mile Island," Science, 204, April 13, 1979, p. 154. This brief article, released shortly after the incident at Three Mile Island, provides a contemporary perspective on the impact of incident on nuclear policy. Carter argues that the public and political fears caused by the incident, regardless of the lack of real danger, resulted in a substantial reduction in the support for nuclear power in politics. Perrow, Charles. Normal Accidents: Living with High Risk Technologies. Princeton: Princeton University Press, 1984. This book, by sociologist Charles Perrow, is an examination of of complex systems and attempts to provide a structure for understanding their failures. Perrow argues that failure is an inevitable part of new complex technological systems such as nuclear power plants. Citing the Three Mile Island incident extensively, he argues that these small failures are part of the process of refining design and cannot be planned around due to them also being tied to the human element of the system. Walker, Samuel. Three Mile Island: A Nuclear Crisis in Historical Perspective. Berkeley: University of California Press, 2004. This book represents one of the most up to date and scholarly works on the subject of Three Mile Island. Using the 25 year gap to provide sufficient space for historical analysis, Walker examines the events of the Three Mile Island meltdown in close detail, focusing heavily on the engineering aspects. After a through examination of events, Walker explores the impact of the incident on politics, culture, and energy policy. While he ultimately finds the dangers of Three Mile Island overstated, he shows how fear, misunderstanding, and a willingness to use fossil fuels crippled the American nuclear power effort.