The Three Mile Island Accident's Impact on U.S. Nuclear Industry

Molly Mitchel
March 12, 2017

Submitted as coursework for PH241, Stanford University, Winter 2017


Fig. 1: Three Mile Island prior to accident. (Source: Wikimedia Commons )

On March 28, 1979, reactor number two of the Three Mile Island Nuclear Station in Dauphin County, Pennsylvania, experienced a partial nuclear meltdown. [1] The accident, classified as the most catastrophic in U.S. nuclear power plant history, began with a series of mechanical failures that employees at the plant were unable to identify as resulting from a loss of coolant. The accident produced radioactive gases that were released into the environment surrounding the plant, but no evidence suggests that the presence of these gasses increased rates of cancer in and around the area. [2] Luckily, the accident led to no deaths or injuries of plant workers or inhabitants of the surrounding area. However, the accident produced a rise in regulations for the nuclear industry, and is often referenced as a factor in the decreasing construction of new nuclear plants that began earlier in the 1970s. [2] Fig. 1 shows Three Mile Island Nuclear Station before the accident.

Impact on U.S. Nuclear Industry

The accident ultimately undermined the legitimacy of the U.S. nuclear sector and the NRC, the federal organization established to guarantee safe operations of companies within the nuclear sector. A year after the accident, public trust in the government to ensure that nuclear power plants operated safely had fallen: only 42% of citizens polled felt that the government could oversee the operation of safe nuclear power plants. [3] This decrease in public confidence in nuclear power had serious consequences for the nuclear power sector, as it threatened the sector's already unsteady economic position. First, bond ratings of nuclear utilities were lowered, which made it more difficult for these companies to both continue and start construction of nuclear power plants. Second, the NRC refused to license and permit new nuclear power plants while the investigation of the Three Mile Island Accident was ongoing. At this time the NRC also rolled out a list of new regulatory requirements for nuclear power plants, forcing the rise of operating costs at plants across the country. [3]

As the investigation of the accident proceeded, it became clear that there were serous communication problems between nuclear utilities themselves and between nuclear utilities and the NRC. First, it became evident that the NRC did not have a systematic way of processing reports from nuclear utilities about reactor incidents. As a result of ignoring details, the NRC was not aware of multiple incidents that occurred at plants across the United States. Second, those in the nuclear utilities industry came to the realization that in the future, the sector as a whole would be judged on the performance of its weakest member. Third, the investigation produced evidence that revealed multiple plants were understaffed, and managers were often not equipped with adequate knowledge to run the plants. [3]

In an effort to respond to the growing public distrust of the nuclear industry, nuclear corporations created a system of industrial associations and networks that would, in theory, compensate for the NRC's problems. In late 1979, the Institute of Nuclear Power Operations (INPO) was established. The association (comprised of nuclear utilities and suppliers) had the mission of identifying problems in operations, management, and construction of nuclear power plants. The INPO also took additional steps to identify technical problems in the industry by researching common technical malfunctions at nuclear power plants and distributing subsequent information about these malfunctions to all plants. [3] In an effort to restore public confidence in the nuclear sector, INPO created the U.S. Committee for Energy Awareness, designed to convince the nation that nuclear power would be made safer. In this way, executives at nuclear utilities were able to pursue a collective strategy devoid of state interference. [3]


Ultimately, the accident at Three Mile Island convinced those in the industry that another accident of the same intensity, or worse, would threaten the very existence of the nuclear sector itself. [2] The only way to guard against this was to improve plant safety, operations, and to create an association - the INPO - that would be able to manage these elements across the industry.

© Molly Mitchel. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.


[1] G. C. Thom et al., "Three Mile Island," Science, 204, 794 (1979).

[2] W. Wood, "Nuclear Liability after Three Mile Island," J. Risk Insur. 48, 450 (1981).

[3] J. Campbell, "Corporations, Collective Organization, and the State: Industry Response to the Accident at Three Mile Island," Soc. Sci. Quart. 70, 650 (1989).