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Hisashi Ouchi: The MOST Radiated Man in the World

The case of Hisashi Ouchi remains infamous in the tales of radiation poisoning
The case of Hisashi Ouchi remains infamous in the tales of radiation poisoning

Hisashi Ouchi, 35, and two other employees were purifying uranium oxide on the morning of September 30, 1999, at a nuclear fuel-processing facility in Tokaimura, Japan, to create fuel rods for a research reactor.

However, things would go horribly wrong.

What Happened in The Tokaimura Nuclear Accidents?

On September 30, 1999, a fuel enrichment plant run by JCO, a Sumitomo Metal Mining Company division, about four miles from the PNC site, experienced the second, more devastating Tokai nuclear accident (the first was in 1997).

Before the Fukushima Daiichi nuclear disaster in 2011, it was the deadliest nuclear radiation accident to affect the civilians of Japan.

Tokaimura power plant

Tokaimura power plant

After the uranium mixture reached criticality, the incident exposed the local populace to dangerous nuclear radiation. Three technicians were mixing fuel, and two of them perished. Lack of regulatory oversight, a poor safety culture, and poor technician training and education all contributed to the event.

Uranium hexafluoride was transformed into enriched uranium dioxide fuel at the JCO facility. The production of nuclear reactor fuel rods for Japan’s power facilities and research reactors began with this.

Precision is necessary for enriching nuclear fuel, and technicians may face extremely high dangers as a result. When nuclear products are combined incorrectly, a fission reaction can occur, resulting in radiation. It takes a specialized chemical purification process to enrich the uranium fuel.

To create uranyl nitrate using nitric acid, the stages included feeding tiny amounts of uranium oxide powder into a specified dissolving tank. The mixture is then carefully moved to a buffer tank that has been made with exceptional care. The buffer tank that holds the combined components is specifically made to stop fission activity before it gets out of control.

Hisashi Ouchi in a file photo

Hisashi Ouchi in a file photo

Ammonia is introduced to a precipitation tank to create a solid product. Any leftover pollutants from nuclear waste are intended to be captured by this tank.

In the final step, uranium oxide is added to the dissolving tanks and allowed to dissolve until it is refined using a wet-process technology developed by Japan without enriching the isotopes.

JCO was under pressure to operate more efficiently, which led to the business using an illegal method in which they omitted numerous crucial phases from the enrichment process. Hand-pouring the product into a precipitation tank from stainless steel buckets was done by technicians.

This procedure unintentionally helped a critical mass-level incident set off several hours of unchecked nuclear chain reactions.

How Did the Tokaimura Nuclear Accident Take Place?

To satisfy shipping requirements, JCO facility technicians Hisashi Ouchi, Masato Shinohara, and Yutaka Yokokawa accelerated the final stages of the fuel/conversion process.

Since it was JCO’s first batch of fuel for the Joyo experimental fast breeder reactor in three years, there needed to be formal training or qualifying standards in place. The team mixed the chemicals in stainless steel buckets for convenience and to speed up the processing procedure. Although they were unaware that the STA had not approved this technique, the workers followed the instructions in the JCO operating handbook.

The nuclear accident made Hisashi Ouchi the most radiated man on the planet

Uranyl nitrate would be kept in a buffer tank and gradually injected into the precipitation tank in 2.4 kg (5.3 lb.) increments under the correct operating technique.

The fill level of the precipitation tank, which contained roughly 16 kg (35 lb.) of uranium, reached criticality in the tall and narrow buffer tank at around 10:35 A.M.

The technicians then added a seventh bucket of aqueous uranyl nitrate, enriched to 18.8% 235U, to the tank, bringing the level to the hazardous level. The amount of solution injected into the tank was about seven times the STA-specified allowable mass limit.

All Hell Breaks Loose

The correct steps for dissolving uranium oxide powder in a designated dissolution tank were mandated by the nuclear fuel conversion requirements listed in the 1996 JCO Operating Manual. The buffer tank’s tall, narrow form was intended to contain the solution and avoid criticality securely. On the other hand, the precipitation tank was intended to retain a limited supply of this kind of solution.

It was favorable to criticality because of its wide cylindrical architecture. The workers added the uranyl nitrate to the precipitation tank instead of the buffer tanks. Instantaneously, uncontrolled nuclear fission started.

On October 2, 1999, residents of Tokaimura, Japan, had their radiation levels examined.

On October 2, 1999, residents of Tokaimura, Japan, had their radiation levels examined.

As a result, a self-sustaining nuclear fission chain formed, producing powerful gamma and neutron radiation. At the time of the incident, Shinohara was standing on a platform to help pour the solution while Ouchi had his body draped over the tank.

Yokokawa was four meters away at a desk. Gamma radiation alarms rang, and all three technicians saw a blue flash (probably Cherenkov radiation). The fission reaction generated ongoing chain reactions over the course of the following several hours.

Radiation Poisoning: Dead Men Walking

Both Ouchi and Shinohara experienced pain, nausea, and breathing difficulties immediately. They both went to the decontamination area, where Ouchi puked. The person who was exposed to the most radiation was Ouchi, who experienced immediate problems with coherence, mobility, and loss of consciousness.

According to an article in the Bulletin of the Atomic Scientists, the personnel accidentally put too much uranium in the tank since they needed to gain prior expertise in handling uranium with that level of enrichment. They unintentionally started an uncontrollable nuclear chain reaction, or what is known as a “criticality accident” in nuclear terms.

In the history of nuclear accidents, Ouchi, who was the closest to the nuclear reaction, likely experienced one of the highest radiation doses. He was going to experience a terrible fate that would serve as a warning about the dangers of the Atomic Age.

The paper in the Bulletin of the Atomic Scientists was co-authored by physicist Edwin Lyman and his colleague Steven Dolley. According to Lyman, “the most obvious lesson is that when you’re working with [fissile] materials, criticality restrictions are there for a reason.”

Hisashi Ouchi being transported to the Tokyo Hospital

Hisashi Ouchi being transported to the Tokyo Hospital

The three workers were forced to leave the premises after excessive levels of gamma radiation reached critical mass and triggered the building’s alarms. The three employees needed to be made aware of the consequences of the event or the requirements for reporting.

An ambulance transported the injured workers to the nearby hospital after a worker in the adjoining building became aware of them and called for help. The fission products contaminated the fuel reprocessing building and the area around the nuclear site.

As soon as they came, emergency service personnel led other plant personnel outside the muster zones.

According to Lyman, a “devastating type of accident” could occur if safety precautions aren’t carefully explained and implemented.

And, as mentioned earlier, this wasn’t the first time something like this was happening. According to a U.S. Nuclear Regulatory Commission report from 2000, 21 other criticality accidents had happened between 1953 and 1997 before Tokaimura.

According to The Post, the two employees departed the room without further ado. However, the harm had already been done. The person who was closest to the reaction, Ouchi, had gotten much radiation. There have been many estimates of the precise dose, but a 2010 presentation by Masashi Kanamori of the Japan Atomic Energy Agency put it at 16 to 25 grey equivalents (GyEq).

Shinohara, who was about 18 inches (46 centimeters) away, received a lower dose. However, one that was still extremely harmful, of about 6 to 9 GyEq, and a third man, who was farther away, was exposed to less radiation.

Hisashi Ouchi in the hospital

Hisashi Ouchi in the hospital

Many online stories refer to Ouchi as “the most radioactive man in history” or something like that, but nuclear scientist Lyman stops shy of that conclusion.

“Although I wonder if it’s the highest, the estimated doses for Ouchi were among the highest known,” according to Lyman. “These frequently happen in these criticality accidents.”

Criticality accidents in nuclear power plants, like the 1986 reactor explosion at Chornobyl in Ukraine, then a part of the Soviet Union, where the radiation was spread, can have doses much worse than catastrophic accidents.

Through a rush of neutrons and gamma rays, “these criticality incidents provide the possibility for delivering a huge amount of radiation in a short period of time,” according to Lyman.

“If you’re close enough, that one burst can expose you to more radiation than a deadly dose in a matter of seconds. So, that’s the frightening aspect of it.”

According to Lyman, high radiation doses harm the body and impair its ability to produce new cells. As a result, the bone marrow, for instance, ceases producing the white blood cells that fight infection and the red blood cells that deliver oxygen.

“If you receive enough ionizing radiation that will damage cells, your organs will not function,” he says. “Your fate is predestined, even though there will be a delay.”

The radioactive personnel was transported to the National Institute of Radiological Sciences in Chiba, a city east of Tokyo, according to an October 1999 story in the medical journal BMJ. It was discovered there that their lymphatic blood count had nearly completely disappeared.

They had diarrhea, dehydration, and nausea. They were moved to the University of Tokyo Hospital three days later, where medical professionals made numerous attempts to save their lives.

Ouchi’s Condition Declines Rapidly

According to “A Slow Death: 83 Days of Radiation Sickness,” a 2002 book by a team of journalists from Japan’s NHK-TV, when Ouchi, a handsome, powerfully built, former high school rugby player with a wife and young son, arrived at the hospital, he didn’t yet look like a victim of intense radiation exposure.

He had no blisters or burns, but his face was slightly red and swollen, and his eyes were bloodshot. He did, however, complain of pain in his hand and ear. Even so, the medical professional who examined him believed it might be possible to save his life.

But the next day, Ouchi’s condition deteriorated. According to the text, he started to require oxygen, and his abdomen grew larger. After he arrived at the University of Tokyo hospital, things got worse. Images of the chromosomes in Ouchi’s bone marrow cells were analyzed by a specialist six days after the incident.

They revealed only sporadic black dots, indicating that they had been fragmented. The body of Ouchi would not be able to produce new cells. Ouchi underwent a peripheral blood stem cell transplant a week after the accident with the help of his sister, who volunteered as a donor.

Hisashi Ouchi in his final days

Nevertheless, Ouchi’s health kept becoming worse. When the medical tape was taken off his chest, he started to complain of being thirsty, and his skin started to come off as well.

He started getting blisters. Tests revealed that the radiation had destroyed the chromosomes necessary for his skin to renew, causing the outer layer of his skin, known as the epidermis, to disappear gradually.

The agony grew worse. He also started having breathing issues. He was forced to be fed intravenously two weeks after the injury because he could not swallow. His heart stopped two months into his ordeal, yet doctors revived him.

At 11:21 p.m. on December 21, Ouchi’s body finally gave out. The article by Lyman and Dolley states that he passed away from multiple organ failure.

According to Japan Times, the country’s prime minister at the time, Keizo Obuchi, released a statement expressing his condolences to the worker’s family and promising to strengthen nuclear safety procedures.

According to The Guardian, Shinohara, Ouchi’s coworker, also passed away in April 2000 due to multiple organ failures.

Picture of a 16 year old boy often mistaken to be Hisashi Ouchi

According to this April 2000 study by the U.S. Nuclear Regulatory Commission, the Japanese government’s inquiry found that the accident’s primary causes included insufficient regulatory control, a lack of a suitable safety culture, and insufficient worker training and certification.

Six employees of the business that ran the plant were accused of professional carelessness and breaking nuclear safety regulations. According to the Sydney Morning Herald, a court fined the corporation and at least one of the officials in 2003 and gave them suspended prison sentences.

The censored images can be accessed here.

Who Is the Person in The Picture Often Mistaken as Hisashi Ouchi?

The photograph of an unnamed 16-year-old boy, a burn victim, was taken at the UTMB campus’s Shriners Hospitals for Children in Galveston, Texas. The Rebecca Sealy building is seen in the photo outside the window.

The photograph was featured in a burn journal called “Treatment of extreme full body trauma, 4th edition, and it proves that the picture is not of Hisashi Ouchi.

The unnamed victim was involved in a housefire

The unnamed victim was involved in a housefire

Since 2008, the image has been making the rounds online. It appears that the absurd notion that it depicts Hisashi Ouchi first appeared around 2010 or 2011. It goes without saying that this notion has previously been thoroughly refuted many times and has been so again.

RIP Hisashi and Masato.

Next, read about the Horrifying Serial Killer: Albert Fish. Then, if you’re interested in more serial killers, I think you’d find the story of Danny Rolling and His Rampage morbidly fascinating!



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Written By

Abin Tom Sebastian, also known as Mr. Morbid in the community, is an avid fan of the paranormal and the dark history of the world. He believes that sharing these stories and histories are essential for the future generations. For god forbid, we have seen that those who forget history are doomed to repeat it.



  1. Saara Torrison

    February 1, 2023 at 4:34 pm

    Wow, great recap. The sheer lack of consequence for the company is unbelievable. It’s awful that they kept him alive and didn’t euthanize him. It must’ve been excruciating.

    • Mr Morbid

      February 2, 2023 at 6:37 am

      Thank you for reading, and the review. It’s a really tragic tale.

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