Three Mile Island accident

Three Mile Island accident
Three Mile Island nuclear facility, c. 1979
DateMarch 28, 1979
(45 years ago) (1979-03-28)
Time04:00 (Eastern Time Zone UTC−5)
LocationLondonderry Township, Dauphin County, Pennsylvania, U.S.
OutcomeINES Level 5 (accident with wider consequences)
DesignatedMarch 25, 1999[1]

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 on the Susquehanna River in Londonderry Township, 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.[2][3] It is the worst accident in U.S. commercial nuclear power plant history.[4] On the seven-point logarithmic International Nuclear Event Scale, the TMI-2 reactor accident is rated Level 5, an "Accident with Wider Consequences".[5][6]

The accident began with failures in the non-nuclear secondary system,[7] followed by a stuck-open pilot-operated relief valve (PORV) in the primary system,[8] 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.[9]

The accident heightened anti-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.[10] Anti-nuclear movement activists expressed worries about regional health effects from the accident.[11] 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.[12][13][14][15][16][17][18] 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 2023).[19] TMI-1 was restarted in 1985, then retired in 2019 due to operating losses. It is expected to go back into service by 2028 as part of a deal with Microsoft to power its data centers.[20]

  1. ^ "PHMC Historical Markers Search". Pennsylvania Historical and Museum Commission. Retrieved January 25, 2014.
  2. ^ Rogovin, Mitchell (January 1980). Three Mile Island: a report to the commissioners and to the public. The problem was caused by a cooling problem and caused some of the core to melt in the 2nd reactor. Volume I. Washington, D.C.: U.S. Nuclear Regulatory Commission. p. 3. doi:10.2172/5395798. OSTI 5395798. Retrieved October 17, 2021.
  3. ^ Rogovin, Mitchell (January 1980). Three Mile Island: a report to the commissioners and to the public. Volume II Part 2 (PDF). Washington, D.C.: U.S. Nuclear Regulatory Commission. p. 309. Retrieved October 17, 2021.
  4. ^ "Backgrounder on the Three Mile Island Accident". U.S. Nuclear Regulatory Commission. Retrieved March 6, 2018.
  5. ^ Spiegelberg-Planer, Rejane (September 2009). "A Matter of Degree" (PDF). IAEA Bulletin. 51 (1). Vienna, Austria: Division of Public Information, International Atomic Energy Agency: 46. Retrieved October 16, 2021. A revised International Nuclear and Radiological Event Scale (INES) extends its reach.
  6. ^ "The International Nuclear and Radiological Event Scale" (PDF). INES. International Atomic Energy Agency. August 1, 2008. Retrieved October 16, 2021. Level 5: Accident with Wider Consequences; Three Mile Island, USA, 1979 – Severe damage to the reactor core.
  7. ^ "Secondary system". U.S. Nuclear Regulatory Commission. March 9, 2021. Retrieved October 16, 2021. The steam generator tubes, steam turbine, condenser, and associated pipes, pumps, and heaters used to convert the heat energy of the reactor coolant system into mechanical energy for electrical generation. Most commonly used in reference to pressurized water reactors.
  8. ^ "Primary system" (PDF). Reactor Concepts Manual, Pressurized Water Reactor. USNRC Technical Training Center. p. 4-3. Retrieved October 16, 2021. The primary system (also called the Reactor Coolant System) consists of the reactor vessel, the steam generators, the reactor coolant pumps, a pressurizer, and the connecting piping. A reactor coolant loop is a reactor coolant pump, a steam generator, and the piping that connects these components to the reactor vessel. The primary function of the reactor coolant system is to transfer the heat from the fuel to the steam generators. A second function is to contain any fission products that escape the fuel.
  9. ^ Walker, J. Samuel (2004). Three Mile Island: A Nuclear Crisis in Historical Perspective. Berkeley, California: University of California Press. p. 211. ISBN 0-520-23940-7. Retrieved October 19, 2021. The commission concluded that Met Ed, GPU, Babcock & Wilcox, and the NRC shared responsibility for the shortcomings in operator training. Those inadequacies were compounded by design flaws that undermined the efforts of the plant staff to deal with the accident. They included the cacophony of undifferentiated alarms, the inconvenient arrangement of instruments and controls, and the absence of clear indicators either of levels of water in the pressure vessel or of the position of the stuck-open PORV.
  10. ^ "Michael Levi on Nuclear Policy". The Economist. March 31, 2011. Archived from the original on April 15, 2011. Retrieved April 6, 2011 – via YouTube.[time needed]
  11. ^ Gofman, John W.; Tamplin, Arthur R. (1979). Poisoned Power: The Case Against Nuclear Power Plants Before and After Three Mile Island (Updated ed.). Emmaus, Pennsylvania: Rodale Press. p. xvii. Retrieved October 1, 2013. ...we arrive at 333 fatal cancers or leukemias.
  12. ^ Hatch, Maureen C.; et al. (1990). "Cancer near the Three Mile Island Nuclear Plant: Radiation Emissions". American Journal of Epidemiology. 132 (3): 397–412. doi:10.1093/oxfordjournals.aje.a115673. PMID 2389745.
  13. ^ Levin, R. J. (2008). "Incidence of thyroid cancer in residents surrounding the Three-Mile Island nuclear facility". Laryngoscope. 118 (4): 618–628. doi:10.1097/MLG.0b013e3181613ad2. PMID 18300710. S2CID 27337295. Thyroid cancer incidence has not increased in Dauphin County, the county in which TMI is located. York County demonstrated a trend toward increasing thyroid cancer incidence beginning in 1995, approximately 15 years after the TMI accident. Lancaster County showed a significant increase in thyroid cancer incidence beginning in 1990. These findings, however, do not provide a causal link to the TMI accident.
  14. ^ Levin, R. J.; De Simone, N. F.; Slotkin, J. F.; Henson, B. L. (August 2013). "Incidence of thyroid cancer surrounding Three Mile Island nuclear facility: the 30-year follow-up". Laryngoscope. 123 (8): 2064–2071. doi:10.1002/lary.23953. PMID 23371046. S2CID 19495983.
  15. ^ Han, Y. Y.; Youk, A. O.; Sasser, H.; Talbott, E. O. (November 2011). "Cancer incidence among residents of the Three Mile Island accident area: 1982–1995". Environ Res. 111 (8): 1230–1235. Bibcode:2011ER....111.1230H. doi:10.1016/j.envres.2011.08.005. PMID 21855866.
  16. ^ Hatch, M. C.; Wallenstein, S.; Beyea, J.; Nieves, J. W.; Susser, M. (June 1991). "Cancer rates after the Three Mile Island nuclear accident and proximity of residence to the plant". American Journal of Public Health. 81 (6): 719–724. doi:10.2105/AJPH.81.6.719. PMC 1405170. PMID 2029040.
  17. ^ "Backgrounder on the Three Mile Island Accident: Health Effects". U.S. Nuclear Regulatory Commission. Retrieved January 13, 2018. The NRC conducted detailed studies of the accident's radiological consequences, as did the Environmental Protection Agency, the Department of Health, Education and Welfare (now Health and Human Services), the Department of Energy, and the Commonwealth of Pennsylvania. Several independent groups also conducted studies. The approximately 2 million people around TMI-2 during the accident are estimated to have received an average radiation dose of only about 1 millirem above the usual background dose. To put this into context, exposure from a chest X-ray is about 6 millirem and the area's natural radioactive background dose is about 100–125 millirem per year for the area. The accident's maximum dose to a person at the site boundary would have been less than 100 milligrams above the background. In the months following the accident, although questions were raised about possible adverse effects from radiation on human, animal, and plant life in the TMI area, none could be directly correlated to the accident. Thousands of environmental samples of air, water, milk, vegetation, soil, and foodstuffs were collected by various government agencies monitoring the area. Very low levels of radionuclides could be attributed to releases from the accident. Comprehensive investigations and assessments by several well-respected organizations, such as Columbia University and the University of Pittsburgh, have concluded that in spite of serious damage to the reactor, the actual release had negligible effects on the physical health of individuals or the environment.
  18. ^ Goldenberg, D, Russo, M, Houser, K, Crist, H, Derr JB, Walter V, Warrick JI, Sheldon KE, Broach J, Bann, DV (2017). "Altered molecular profile in thyroid cancers from patients affected by the Three Mile Island nuclear accident". Laryngoscope. 127 supplement 3: S1–S9. doi:10.1002/lary.26687. PMID 28555940. S2CID 40795419. Findings were consistent with observations from other radiation-exposed populations. These data raise the possibility that radiation released from [Three Mile Island] may have altered the molecular profile of [thyroid cancer] in the population surrounding TMI.
  19. ^ "14-Year Cleanup at Three Mile Island Concludes". The New York Times. August 15, 1993. Retrieved March 28, 2011.
  20. ^ Sherman, Natalie (September 20, 2024). "Microsoft chooses infamous nuclear site for AI power". BBC News. Retrieved September 20, 2024.