← Half-Life Histories · Season 1

Tokaimura Tragedy - History's Worst Criticality Accident

S1 · E29 · 17 Mar 2026 · 29 min

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On September 30, 1999, the Tokaimura nuclear accident became the worst criticality accident in modern nuclear history. At a uranium processing facility in Japan, workers accidentally triggered a self-sustaining nuclear reaction while preparing fuel for an experimental reactor. One of the technicians, Hisashi Ouchi, received a massive radiation dose and spent 83 days in intensive medical care before his death. Over time, his story spread across the internet with misleading claims about what really happened. This [HALF-LIFE HISTORY] is the true story.