Overview
- Workers poured about seven times the permitted uranium into a processing tank, triggering an uncontrolled chain reaction marked by a blue flash.
- Hisashi Ouchi, 35, was exposed to an estimated 17,000 mSv, described as 850 times the safe annual worker limit and far above typical post‑Chernobyl resident exposure.
- Ouchi was hospitalized in Tokyo with near‑zero white blood cells and severe radiation burns, and doctors attempted stem cell transplants and skin grafts over 83 days.
- He died on December 21, 1999 of multiple organ failure; coworker Masato Shinohara died in April 2000, while supervisor Yutaka Yokokawa survived.
- A government probe cited weak regulation, poor safety culture, and inadequate training; the plant had a 1997 fire that exposed 37 staff, and six officials later received suspended prison terms.