Three Mile Island, Pennsylvania, United States

On March 28, 1979, Three Mile Island's nuclear power plant unit 2 (almost 1000 MW) suffered the US worst commercial nuclear accident. Radiation was released. Many people were evacuated. The effects were felt in the country and abroad.


The Three Mile Island Unit 2 (TMI-2) reactor, near Middletown, Pa., on the Susquehanna River,  partially melted down on March 28, 1979. The accident showed that there were enormous risks from  nuclear power plants. It enhanced safety concerns among activists and the general public, resulted in new regulations for the nuclear industry, and contributed to the decline of reactor construction programs in the US and in some other countries. It gave a great impulse to the anti-nuclear movement, and discredited previous risk assessments such as the notorious 1975 Rasmussen Report sponsored by the U. S. Atomic Energy Commission statistically estimating extremely low risks from potential accidents in commercial nuclear power plants. It was carried out under the direction of Norman C. Rasmussen of the Massachusetts Institute of Technology. The risks had to be estimated, rather than measured, because although there were about 50 such plants operating, there had not been grave nuclear accidents in commercial reactors in the U.S. before the Three Mile Island meltdown. On March 30, 1979, Gov. Richard Thornburgh recommended an evacuation for preschool children and pregnant women living within five miles of Three Mile Island. According to some research, data collected since the meltdown  demonstrate a significant nexus between radiation exposure and adverse health impacts to women and children.  The US – until the accident - was expecting to derive about 14 percent of its generating capacity from nuclear power stations. The US industry had begun confidently taking new orders totaling 8,000 MW that year – more than any year since 1974. Instead, after Three Mile Island,  president Carter ordered an inquiry into the accident and said he would expedite efforts to expand the number of nuclear inspectors. But mid-April he added that “there is no way for us to abandon nuclear power in the foreseeable future,”

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Basic Data
NameThree Mile Island, Pennsylvania, United States
CountryUnited States of America
Accuracy of LocationHIGH local level
Source of Conflict
Type of Conflict (1st level)Nuclear
Type of Conflict (2nd level)Nuclear power plants
Specific CommoditiesUranium
Project Details and Actors
Project DetailsEstimated costs. Three Mile Island-1 (TMI-1) came on line in September 1974 at a cost of $400 million. Three Mile Island-2 (TMI-2) came on line in December 1978, its costs went over budget.. The plant had been online for just 90 days before the March 1979, accident. Then, at least one billion dollars has been spent to defuel the facility. TMI-2 cost is then close to $2 billion dollars in construction and cleanup bills.

A federal appeals court in December 2003 dismissed the consolidated cases of 2,000 plaintiffs seeking damages against the plant’s former owners. The court said the plaintiffs failed to present evidence they had received a radiation dose large enough to possibly cause health effects.

At the time of the accident in March 1979, Three Mile Island units 1 and 2 were owned by three utilities operating in two states, i.e., Metropolitan Edison (50 percent), Jersey Central Power & Light (25 percent) and Pennsylvania Electric (25 percent). The companies were organized under the General Public Utilities holding company umbrella.

A federal appeals court in December 2003 dismissed the consolidated cases of 2,000 plaintiffs seeking damages against the plant’s former owners. The court said the plaintiffs failed to present evidence they had received a radiation dose large enough to possibly cause health effects.

100,000 people are said to have fled to Harrisburg and nearby on the days of the accident. (

Unit 2 was operating at its full capacity of 959 megawatts. Unit 2 of TMI was permanently closed after the accident, Unit 1 was started again only after some time, adding to the costs.

There is a continuing debate on the health consequences of the accident on the surrounding populations. The accident implied a decisive impulse to the anti-nuclear movement in the US and other countries.
Level of Investment (in USD)2,000,000,000
Type of PopulationSemi-urban
Potential Affected Population100,000
Start Date28/03/1979
Company Names or State EnterprisesMetropolitan Edison from United States of America
Relevant government actorsPresident Jimmy Carter of the USA (visited the site two days afterwards)

Governor of Pennslvania, W. Scranton
Environmental justice organisations and other supportersTMI Alert

Wise International
The Conflict and the Mobilization
Intensity of Conflict (at highest level)HIGH (widespread, mass mobilization, violence, arrests, etc...)
When did the mobilization beginMobilization for reparations once impacts have been felt
Groups MobilizingInternational ejos
Local ejos
Local government/political parties
Local scientists/professionals
Forms of MobilizationCommunity-based participative research (popular epidemiology studies, etc..)
Creation of alternative reports/knowledge
Development of a network/collective action
Involvement of national and international NGOs
Lawsuits, court cases, judicial activism
Media based activism/alternative media
Official complaint letters and petitions
Public campaigns
OtherRadiation, nuclear accident (meltdown)
Health ImpactsVisible: Exposure to unknown or uncertain complex risks (radiation, etc…), Mental problems including stress, depression and suicide
Potential: Occupational disease and accidents, Other Health impacts
Socio-economic ImpactsVisible: Displacement, Specific impacts on women
Potential: Violations of human rights, Other socio-economic impacts
OtherPregnant women in a 5 mile radius were evacuated
Project StatusStopped
Pathways for conflict outcome / responseCourt decision (undecided)
Withdrawal of company/investment
Do you consider this as a success?No
Why? Explain briefly.The local people suffered a great risk of damage and perhaps actual damage, without enough recognition, in their own view. The accident was a strong deterrent to the building of nuclear power plants in the US and other countries.
Sources and Materials

Dickinson College website, information on the accident from a small college not far away
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World Information Service on Energy, founded in 1978. Several reports on the case. A good source for nuclear energy for many years.
[click to view]

Interview with William Scranton III, at the time Lieutenant Governor of Pennsylvania, who visited the site
[click to view]

Wise International. The curse of Three Mile Island. Nuclear Monitor Issue: #685.

[click to view]

"Crisis at Three Mile Island". Very full contemporary account of the events and its aftermath, several episodes in The Washington Post.
[click to view]

The New York Times, the day after the accident
[click to view]

Media Links

TV Interview with transcript, Amy Goodman and Harvey Wasserman, 30th anniversary of the accident
[click to view]

Bulletin with many news from the Three Mile Island Alert, directed by Eric Epstein
[click to view]

Dickinson College, Three Mile Island emergency, description of the accident
[click to view]

Documentary, The Meltdown
[click to view]

Other Documents

[click to view]

Meta Information
Last update23/11/2016