In September 1999, 35-year-old Hisashi Ouchi was working at the Tokaimura nuclear power plant in Japan when he was exposed to the highest level of radiation any human had ever survived—at least temporarily. He and two coworkers accidentally triggered a fission reaction by mixing too much enriched uranium in a single tank. A blue flash of Cherenkov radiation erupted, and Ouchi was hit with an estimated dose of 17 sieverts. For context, 8 sieverts is considered 100% fatal. He was rushed to the hospital, where doctors discovered that most of his white blood cells were gone and his chromosomes had been shredded. His skin began to fall off, his organs slowly failed, and his body stopped producing new blood cells entirely. Despite his condition, he remained conscious in the early days, speaking with his family and asking the doctors to stop the pain. But under pressure to study the limits of radiation exposure, doctors kept him alive for 83 days using transplants, machines, and intensive interventions. His condition deteriorated to the point where his skin would slide off at a touch and his body began leaking fluids uncontrollably. He suffered multiple cardiac arrests and was revived each time. Eventually, on December 21, 1999, he died of multi-organ failure. The incident led to public outrage in Japan and forced major reforms in nuclear safety regulations.