Three Mile Island Nuclear Accident

Mehraan Keval
May 15, 2018

Submitted as coursework for PH241, Stanford University, Winter 2018

Fig. 1: The Three Mile Island Nuclear Facility (Source: Wikimedia Commons)

In March of 1979, a combination of stuck valves, misread gauges and human error led to a partial meltdown of the reactor core and subsequent radioactive gas release into the atmosphere at the Three Mile Island nuclear plant near Harrisburg, Pennsylvania, shown in Fig. 1. After the fission reaction was shut down, the TMI-2 reactor's fuel core became uncovered, more than one third of the fuel melted, and inadequate instrumentation and training prevented the operators ability to respond to the accident. To worsen the situation, the accident was accompanied by poor communication and conflicting reports around the details of the disaster, deepening the public's fear of nuclear catastrophe. In response to the accident, President Jimmy Carter appointed a 12-member commission, headed by former Dartmouth President John Kemeny, to investigate the incident and the possible health effects on plant personnel. [1] Although the health effects on residents of the nearby area weren't consequential, the Three Mile Island nuclear accident heightened public fears of nuclear energy and would function to bolster the anti-nuclear sentiment and the American nuclear industry's trajectory. [2]

According to the IAEA, the Three Mile Island accident was a significant deterrent and turning point in global development of nuclear power; Following the incident, the number of reactors under construction decreased every year for nearly two decades. The Three Mile Island nuclear accident resulted in the near-total devastation of the nuclear power industry, as the disaster tipped the scales in the debate around nuclear power to favor those who opposed it. [1] Federal requirements and regulations were resultantly put into place that considerably lengthened construction time and drove up costs. The Three Mile Island Nuclear Crisis, and the resulting public skepticism and fear of a potential nuclear catastrophe, were the impetus for the continuing improvement and regulation of nuclear power plants. [3] This case is of extreme significance as its legacy informs our interaction with nuclear energy in the modern day, and the questions and skepticism around the realm of nuclear energy have carried over as well.

The history of the Three Mile Island nuclear catastrophe cannot be removed from the context of the broader history of nuclear development in the United States. Under the leadership of President Franklin Roosevelt, The United States first began developing nuclear weapons during World War II to combat the hypothetical potential of a nuclear-equipped Nazi Germany. These efforts would amalgamate in 1942 to become the Manhattan Project, a joint venture between America, Britain, and Canada. By 1945 the United States became the first nuclear state in the world, and in the bombings of Hiroshima and Nagasaki that year, the world was first exposed to the immense destructive capacity of nuclear technology. The use of nuclear technology has been a part of the national discourse ever since its advent, with staunch debate about its potential benefits and potential dangers.

In 1957, the SM-1 Nuclear Reactor in Fort Belvoir, Virginia was the first atomic power generator to go online and provide energy in the United States. Throughout the rest of the 1950s and through the 1960s, there was strong support for nuclear energy, with the Atomic Energy Commission predicting that more than 1,000 reactors would be operational in the United States by the year 2000. In the same time frame, nuclear energy also faced considerable opposition in the United States. Pacific Gas and Electric planned to build the first commercially viable nuclear power plant at Bodega Bay, just north of San Francisco. The proposal was controversial, and following conflict with local citizens, the plans for the plant were abandoned in 1964. This can largely be seen as the beginning of the anti-nuclear movement's success. In the 1970s and 1980s, there were many public anti nuclear protests in the United States, indicating that support for nuclear technology was on the decline before the incident at Three Mile Island. As stated in the background section, the Three Mile Island accident was the most significant accident in US commercial nuclear power plant history. The Three Mile Island Nuclear Generating Station (TMI) houses two separate units, TMI-1 and TMI-2. TMI-1 first came online in 1974, and TMI-2 began commercial operation in 1978. After the accident in at TMI in March of 1979, concerns about nuclear accidents, proliferation, economic feasibility, and waste disposal and the subsequent widespread fear of nuclear technology significantly crippled the nuclear energy industry. [1]

To frame this incident in the broader scope of its place in US History, it is important to note that the TMI incident was part of a turbulent time. The end of Jimmy Carter's presidency (1979-1981) was marked by a number of crises in succession. The Iran hostage crisis, a diplomatic standoff between the United States and Iran over 52 Americans being held hostage in Iran, as well as the energy crisis of 1979 in which the nation's oil supply decreased in the wake of the Iranian Revolution, both occurred within a year of the TMI accident. Furthermore, the Soviet Invasion of Afghanistan resulted in escalation of the Cold War and the formal end of détente. While TMI was an isolated incident and was significant in and of itself, taken in concert with the escalating tension between the Soviet Union and the United States and general turbulence nature of the time, it becomes clear that TMI was a turning point in the United States Nuclear energy trajectory. After the Three Mile Island (or TMI) accident, public support for nuclear energy fell from an all-time high of 69 percent in 1977 to 46 percent in 1979. Approximately two million people were exposed to radiation in small amounts, and public support for the use of nuclear energy fell from what was previously an all-time high of 69% in 1977 to 46% in 1979. [4]

© Mehraan Keval. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. 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] "Three Mile Island," U.S. Nuclear Regulatory Commission, February 2013.

[2] "Three Mile Island: A Chronology," Washington Post, 28 Mar 89.

[3] N. Hultman and J. Koome, "Three Mile Island: The Driver of US Nuclear Power's Decline?" Bull. Atom. Sci. 69, No. 3, 63 (2013).

[4] T. Blackwood, U.S. Opinion of Nuclear Energy in the Wake of Three Mile Island," Physics 241, Stanford University, Winter 2017.