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Cautionary Tales · June 15, 2020 · 38m
The Nuclear Operator's Nightmare
Cautionary Tales
The Three Mile Island accident of 1979 — how a series of minor malfunctions, combined with operator confusion and misleading instrument readings, nearly caused a full nuclear meltdown in Pennsylvania.
Highlights
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Complex systems fail because operators can't see the system — they can only see their instruments
At Three Mile Island, the reactor was losing coolant but the instruments showed the opposite. The operators made rational decisions based on wrong information because the instruments were designed for normal operations, not emergencies.•
Near-misses should be treated as failures, not successes — TMI was narrowly averted but the lessons weren't learned
TMI was eventually brought under control, so it was treated as a 'near miss' — a success story. But the same failure modes persisted in nuclear operations worldwide because the near-miss was rationalized rather than studied.