Three Mile Island (1979)
Partial core meltdown caused by cooling system malfunction and operator error. Approximately 700,000 gallons of radioactive water released into the Susquehanna River. No direct deaths attributed. Unit 2 permanently shutdown; cleanup completed by 1993. TMI-1 continued operation until 2019.
Key Stats
100/100
Three Mile Island (1979)
Location: Dauphin County, Pennsylvania, USA Reactor: TMI Unit 2 (PWR, 906 MWe) INES Rating: INES Level 5
Summary
Partial core meltdown caused by cooling system malfunction and operator error. Approximately 700,000 gallons of radioactive water released into the Susquehanna River. No direct deaths attributed. Unit 2 permanently shutdown; cleanup completed by 1993. TMI-1 continued operation until 2019.
Industry Impact
Led to major reforms in NRC regulations, operator training requirements, and emergency response planning. Shaped US public perception of nuclear power for decades.
Incident reference · Second Atomic Age Nuclear Wiki Source: IAEA, NRC, WNA public records Last updated: 2026-05-10
Sources
- IAEA - Three Mile Island Accident [UNVERIFIED] — Overview of the Three Mile Island accident from the International Atomic Energy Agency.
- NRC - Three Mile Island Accident — Detailed fact sheet and historical review by the U.S. Nuclear Regulatory Commission.
- Wikipedia - Three Mile Island Accident — Comprehensive public encyclopedia entry on the 1979 incident.
- NRC - Report of the President's Commission on the Accident at Three Mile Island [UNVERIFIED] — Official report from the Kemeny Commission, established to investigate the accident.
- World Nuclear Association - Three Mile Island Accident — Summary of the incident and its impact on nuclear safety from the WNA.
Sources (1)
Related Notes
Fukushima Daiichi (2011)
9.0 Mw Tōhoku earthquake and tsunami disabled cooling systems at four BWR units. Units 1–3 experienced fuel meltdowns; Unit 4 spent fuel pool at risk. ~154,000 evacuated. No direct radiation deaths; significant economic and psychological impact. Cleanup expected to take decades.
incidentsChernobyl (1986)
Steam explosion and fire during a poorly conducted safety test destroyed Reactor 4. Positive void coefficient of RBMK design allowed runaway power surge. 31 direct deaths (2 from explosion, 29 from acute radiation syndrome). Estimated 350,000+ evacuated. Exclusion zone remains.