Short Stuff: Hisashi Ouchi

On September 30, 1999, a 35-year-old Japanese nuclear worker named Hisashi Ouchi received a dose of radiation so massive that doctors later described his chromosomes as "completely shattered." He did not die immediately. Instead, he endured 83 days of agony in a Tokyo hospital while doctors tried experimental treatments on a body whose cells could no longer repair themselves. His case has become a grim landmark in the history of nuclear accidents—not because of an explosion or a meltdown, but because of a chain reaction that started in a stainless steel bucket.

The Tokaimura Criticality Accident

Ouchi worked at a fuel processing plant in Tokaimura, Japan, owned by a company called JCO. The plant did not generate nuclear power; it processed uranium oxide into usable uranium-235 fuel for nuclear reactors. On the morning of September 30, 1999, Ouchi and two coworkers were dissolving uranium oxide in a geometrically safe vessel—the approved procedure—to produce uranyl nitrate solution. But JCO had instructed them to bypass the approved method. Instead of using the buffer tank and transferring small amounts into a precipitation tank, they were told to mix the solution in stainless steel buckets and pour it directly into the precipitation tank. And they were told to pour a lot: the seventh bucket brought the total uranium in the tank to 16.6 kilograms—about seven times the 2.4-