Three Mile Island

Extracted Attributes

• Location

  Londonderry Township, Dauphin County, Pennsylvania, United States

• Water Body

  Susquehanna River

• Coordinates

  40.1458187, -76.7243691

• Associated Facility

  Three Mile Island Nuclear Generating Station

• Accident Severity Rating

  Level 5 (Accident with Wider Consequences) on the International Nuclear Event Scale

Timeline

• Unit 1 (TMI-1) of the Three Mile Island Nuclear Generating Station is commissioned for use. (Source: Web Search (State Library of Pennsylvania))

  1974-01-01

• Unit 2 (TMI-2) of the Three Mile Island Nuclear Generating Station is commissioned for use. (Source: Web Search (State Library of Pennsylvania))

  1978-01-01

• A partial nuclear meltdown occurs at the Unit 2 reactor, releasing radioactive gases and marking the worst commercial nuclear accident in U.S. history. (Source: Wikipedia)

  1979-03-28

• Cleanup operations officially begin at the damaged TMI-2 reactor. (Source: Wikipedia)

  1979-08-01

• The undamaged Unit 1 reactor (TMI-1) is restarted and resumes operations. (Source: Wikipedia)

  1985-01-01

• The cleanup of TMI-2 is officially completed at a total cost of approximately $1 billion. (Source: Wikipedia)

  1993-12-01

• TMI-1 is retired from service due to ongoing operating losses. (Source: Wikipedia)

  2019-01-01

• TMI-1 is expected to return to service to supply power to Microsoft data centers under a deal with Constellation Energy. (Source: Wikipedia)

  2027-01-01

Three Mile Island accident

The Three Mile Island accident was a partial nuclear meltdown of the Unit 2 reactor (TMI-2) of the Three Mile Island Nuclear Generating Station, located on the Susquehanna River in Londonderry Township, Dauphin County near Harrisburg, Pennsylvania. The reactor accident began at 4:00 a.m. on March 28, 1979, and released radioactive gases and radioactive iodine into the environment. It is the worst accident in U.S. commercial nuclear power plant history, although its small radioactive releases had no detectable health effects on plant workers or the public. The accident was the largest release of radioactive material in U.S. history until it was exceeded by the Church Rock uranium mill spill four months later. On the seven-point logarithmic International Nuclear Event Scale, the TMI-2 reactor accident is rated Level 5, an "Accident with Wider Consequences". The accident began with failures in the non-nuclear secondary system, followed by a stuck-open pilot-operated relief valve (PORV) in the primary system, which allowed large amounts of water to escape from the pressurized isolated coolant loop. The mechanical failures were compounded by the initial failure of plant operators to recognize the situation as a loss-of-coolant accident (LOCA). TMI training and operating procedures left operators and management ill-prepared for the deteriorating situation caused by the LOCA. During the accident, those inadequacies were compounded by design flaws, such as poor control design, the use of multiple similar alarms, and a failure of the equipment to indicate either the coolant-inventory level or the position of the stuck-open PORV. The accident heightened nuclear safety concerns among the general public and led to new regulations for the nuclear industry. It accelerated the decline of efforts to build new reactors. Anti-nuclear movement activists expressed worries about regional health effects from the accident. Some epidemiological studies analyzing the rate of cancer in and around the area since the accident did determine that there was a statistically significant increase in the rate of cancer, while other studies did not. Due to the nature of such studies, a causal connection linking the accident with cancer is difficult to prove. Cleanup at TMI-2 started in August 1979 and officially ended in December 1993, with a total cost of about $1 billion (equivalent to $2 billion in 2025). TMI-1 was restarted in 1985, then retired in 2019 due to operating losses. It is expected to return to service in either 2027 or 2028 as part of a deal to power Microsoft data centers.

Web Search Results

• Three Mile Island Collection - State Library of Pennsylvania

  The Three Mile Island Nuclear Generating Station was a nuclear energy power station in Middletown, PA, close to the state capital of Harrisburg. Also known simply by the initials TMI, the nuclear station was comprised of the two units TMI-1 and TMI-2, commissioned for use in 1974 and 1978 (respectively). The nuclear station was notable for a serious nuclear accident on March 28, 1979. Equipment failures, design flaws, and operator mistakes resulted in loss of coolant and reactor core meltdown in Unit 2. The accident resulted in extensive studies and commissions by government agencies including the Environmental Protection Agency, the Nuclear Regulatory Commission, the Department of Health, the Department of Energy, etc. Although there was no detectable contamination of radiation into [...] The Three Mile Island Nuclear Generating Station was a nuclear energy power station in Middletown, PA, close to the state capital of Harrisburg. Also known simply by the initials TMI, the nuclear station was comprised of the two units TMI-1 and TMI-2, commissioned for use in 1974 and 1978 (respectively). The nuclear station was notable for a serious nuclear accident on March 28, 1979. Equipment failures, design flaws, and operator mistakes resulted in loss of coolant and reactor core meltdown in Unit 2. The accident resulted in extensive studies and commissions by government agencies including the Environmental Protection Agency, the Nuclear Regulatory Commission, the Department of Health, the Department of Energy, etc. Although there was no detectable contamination of radiation into [...] The Three Mile Island (TMI) Collection at the State Library of Pennsylvania contains federal and corporate documents, transcripts, maps, and other records pertaining to Three Mile Island Nuclear Generating Station near Harrisburg. Mixed-in and inventoried with the Three Mile Island Collection are similar records from the Peach Bottom Nuclear Generating Station in York County. The TMI collection contains reports, transcripts correspondence, surveys, maps, charts, and other records. These records were created and published primarily by two entities: the energy utility companies controlling the nuclear facilities (for example, Metropolitan Edison or General Public Utilities), and the federal agencies responsible for oversight (the United States Nuclear Regulatory Commission, and earlier the

• Three Mile Island Accident | Power and Energy | Research Starters | EBSCO Research

  # Three Mile Island Accident The Three Mile Island accident, which occurred on March 28, 1979, at the nuclear power plant near Harrisburg, Pennsylvania, represents a critical moment in the history of the nuclear energy industry. A malfunction in Unit Two nearly led to a catastrophic meltdown, highlighting significant flaws in plant design, operation, and emergency preparedness. The crisis began with a failure in the cooling system, resulting in the release of radioactive gases and significant public alarm. In response to the escalating situation, Governor Dick Thornburgh ordered the evacuation of vulnerable populations, although a full evacuation was deemed unnecessary due to fears of panic. [...] ### Key Figures ### Summary of Event On March 28, 1979, the Three Mile Island (TMI) nuclear power plant on the Susquehanna River near Harrisburg, Pennsylvania, nearly suffered a catastrophe as its Unit Two malfunctioned, setting into play events that resulted in the most serious accident to that time in the history of the commercial nuclear power industry. Had it not finally been contained, the malfunction would have resulted in devastation similar to that caused by the plant in Chernobyl, Ukraine, in 1986. [...] U.S. General Accounting Office. Three Mile Island: The Most Studied Nuclear Accident in History. Washington, D.C.: Author, 1980. This inquiry was made to determine whether the investigations done up to that time were thorough and accurate in their presentation of the facts and their conclusions as to the causes of the accident. Eight investigative reports, as well as other materials, were reviewed, and although reports varied as to depth and detail, the facts and conclusions were determined to be consistent. Equipment breakdowns, insufficient training of operators, poor design, and inadequate emergency and operating procedures were the chief culprits. Blame was also placed on the Nuclear Regulatory Commission with its poor structure, practices, and attitudes.

• Three Mile Island accident | 1979, Pennsylvania, US | Britannica

  The Three Mile Island power station was named after the island on which it was situated in the Susquehanna River near Harrisburg, Pa. At 4:00 am on March 28, an automatically operated valve in the Unit 2 reactor mistakenly closed, shutting off the water supply to the main feedwater system (the system that transfers heat from the water actually circulating in the reactor core). This caused the reactor core to shut down automatically, but a series of equipment and instrument malfunctions, human errors in operating procedures, and mistaken decisions in the ensuing hours led to a serious loss of water coolant from the reactor core and a partial core meltdown. As a result, the core was partially exposed, and the zirconium cladding of its fuel reacted with the surrounding superheated steam to [...] Britannica Editors History Three Mile Island accident, accident in 1979 at the Three Mile Island nuclear power station that was the most serious in the history of the American nuclear power industry. [...] Key People: : Bruce Babbitt See all related content Temelín Nuclear Power Plant, South Bohemia, Czech Republic More From Britannica nuclear reactor: Three Mile Island and Chernobyl Three Mile Island nuclear power generating station The accident increased public fears about the safety of nuclear reactors and strengthened public opposition to the construction of new plants. The unharmed Unit 1 reactor at Three Mile Island did not resume operation until 1985. The cleanup of Unit 2 continued until 1990; damage to the unit was so severe, however (52 percent of the core melted down), that it remained unusable. The Editors of Encyclopaedia BritannicaThis article was most recently revised and updated by The Editors of ProCon.

• Three Mile Island - Accident, Nuclear & Meltdown | HISTORY

  # Three Mile Island 1 The China Syndrome 2 Three Mile Island Accident 3 TMI Impact 4 Three Mile Island Cleanup 5 Anti-Nuclear Movement 6 Three Mile Island Today 7 Sources Three Mile Island is the site of a nuclear power plant in south central Pennsylvania. In March 1979, a series of mechanical and human errors at the plant caused the worst commercial nuclear accident in U.S. history, resulting in a partial meltdown that released dangerous radioactive gasses into the atmosphere. Three Mile Island stoked public fears about nuclear power—since the accident, construction has not begun at any new nuclear power plant sites in the United States. ## The China Syndrome

• Meltdown at Three Mile Island | American Experience | PBS

  Meltdown at Three Mile Island... It was built on a sandbar called Three Mile Island, in the middle of Pennsylvania's Susquehanna River, just 10 miles downstream from the state capitol of Harrisburg. The plant's state-of-the-art Unit-2 reactor had been generating electricity for nearly a year. Mike Pintek, Reporter Three Mile Island was something you would go to the river and would say wow, look at that power plant, look at those big steam towers. I was jut amazed, wide-eyed, looking at the thing and it was just kind of neat -- it was high technology and this was going to be power that was too cheap to meter. People in the communities surrounding the plant had grown accustomed to the giant concrete fortress. For them, Wednesday, March 28, 1979 began like any other day. [...] - [x] or search all of PBS Live TV PBS Shows My Station My List Shop Donate Sign in Skip To Content Join the Conversation and David Steward, and narrated by Liev Schreiber. For nearly a year the nuclear plant had been quietly generating electricity in the middle of the Susquehanna River. Located just ten miles from the state capital of Harrisburg, Three Mile Island was within 100 miles of Philadelphia, Baltimore, and Washington, DC. People in the surrounding communities had grown accustomed to the concrete fortress with its giant cooling towers. "I was just amazed, wide-eyed looking at the thing, and it was just neat," says Mike Pintek, a local resident and journalist. "It was high technology and this was going to be power that was too cheap to meter." [...] William Scranton Lt. Governor It occurred to me, "Someone's got to go down there and look at that place and see it." And, ah -- and I being, you know, 30 years old (Laughs) and maybe thinking I was more immortal than I really was, said, "I'm going to go down there." William Scranton Three Mile Island was in the middle of the Susquehanna River in the middle of farm country. So it's not like you've got a lot of large buildings around. I mean you just drive up and there they are. They're magnificently huge, beautifully engineered symbols of the power of technological society, to do good and the power of technological society to do harm. And right now you know something's going on in there that you don't understand and it can be very dangerous.

• Instance Of

  Q4167410