Government or official record
Backgrounder on the Three Mile Island Accident
U.S. Nuclear Regulatory Commission
Where this source supports the record
Each entry separates the article’s editorial relevance note from its exact, section-level claims. A bibliography link without a direct claim is labeled plainly.
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Engineering failures · 28 March–2 April 1979Open article references →
The Three Mile Island Nuclear Accident
Three Mile Island Unit 2 reactor · United States
Why editors use it hereOfficial sequence, core damage, releases, health findings, cleanup, and regulatory changes.
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Quick read
On 28 March 1979, equipment failure and operator misinterpretation at Three Mile Island Unit 2 caused loss of reactor coolant and a partial core meltdown.
Reviewed 26 July 2026 -
Trigger and conditions
A failure in the secondary cooling system shut the turbine and reactor.
Reviewed 26 July 2026 -
Uncertainty
Official and major scientific reviews found releases too small to produce detectable population-wide health effects, while some community studies and residents dispute that conclusion.
Reviewed 26 July 2026 -
Why it matters
Three Mile Island demonstrates that a minor component failure becomes major when interface design, training, shared lessons, and crisis communication do not support accurate diagnosis.
Reviewed 26 July 2026
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Quick read