Hisashi Ouchi was one of the technicians working at a facility operated by JCO (formerly Japanese Nuclear Fuel Conversion Co.) in Tokai of Ibaraki Prefecture. He is one of the two fatalities of Tokaimura nuclear accident that exposed him to, perhaps, the highest amount of radiation any human had exposed so far. The ethical value of his prolonged treatment and efforts to keep him alive, that lasted for almost three months despite his wishes and the pain he had to endure, was questioned and the efforts received criticism.

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The accident occurred on September 30, 1999, when Hisashi Ouchi and two of his colleagues added a seventh bucket of aqueous uranyl nitrate solution to a precipitation tank. Upon adding, the tank reached a critical stage and went into a self-sustaining nuclear fission chain reaction releasing intense gamma and neutron radiation.

Hisashi Ouchi, Masato Shinohara, and Yutaka Yokokawa were preparing a small batch of fuel, the first in three years, for the Joyo experimental fast breeder reactor. Ouchi was the nearest to the precipitation tank, while Shinohara was standing on a platform and Yokokawa was sitting at desk four meters away. When the tank reached criticality, they saw a blue flash, possibly Cherenkov radiation, when the gamma-radiation alarms went off. This is the second Tokaimura nuclear disaster to occur and is considered the worst civilian nuclear accident in Japan before Fukishima Daiichi nuclear disaster. It also raised concerns over the lack of proper training and security measures in nuclear plants at that time.

During the accident, Ouchi was exposed to 17 sieverts of radiation with 8 sieverts being normally considered fatal and 50 milli sieverts being the maximum limit of annual dose allowed for Japanese nuclear workers.

The bucket of aqueous solution poured into the tank contained 16 kg of uranium while precipitation tank’s uranium limit was only 2.4 kg. Ouchi received 17 sieverts (sv) of radiation, Shinohara received 10 sv and Yokokawa 3 sv. Ouchi experienced pain, nausea, and breathing difficulties immediately and lost consciousness in the decontamination chamber after vomiting. Though there was no explosion, there was a progressive release of heavy fission products and the chain reaction lasted for almost 20 hours.

Ouchi’s exposure to the radiation was so severe that his chromosomes were destroyed and his white blood cell count plummeted to near-zero. Most of his body had severe burns and his internal organs received severe damage.

Ouchi is considered the first fatality of his kind in Japan, perhaps the only person to ever receive such a huge amount of radiation in such a short amount of time. The amount of radioactive energy that he was exposed to is thought to be equivalent to that at the hypocenter of Hiroshima atomic bombing. The immensity of radiation completely destroyed his body, including his DNA and immune system. According to the book A Slow Death: 83 Days of Radiation Sickness, “one of Ouchi’s chromosomes could be identified or arranged in order.”



What was cruel that he was resuscitated on the 59th day when his heart stopped three times within a period of 49 minutes, despite wishing not to be let to suffer.

As his condition worsened, he was transferred to the University of Tokyo Hospital and, reportedly, underwent the world’s first transfusion of peripheral stem cells. He was also given many blood transfusions, fluids, and medicine that wasn’t even available in Japan yet. He also had to undergo several skin transplants which couldn’t help the loss of fluids through pores. After being treated for a week, Ouchi managed to say, “I can’t take it anymore… I am not a guinea pig”. However, the doctors kept treating him and taking measures to keep him alive, which only ensured a very slow and very painful death.

After 83 days of struggle, Ouchi died of multiple organ failure on December 21, 1999.

On November 27, Ouchi’s heart failed for 70 minutes, but the doctors managed to keep him alive with blood transfusions, fluids, and various drugs to keep his blood pressure and pulse stable. Finally, on December 21, his heart failed and the doctors did not resuscitate saying that his family wanted him to have a peaceful death.

Also watch: David Hahn, The 17-year-old Who Built A Backyard Nuclear Reactor