
Imagine you are working at the nuclear plant. You are a responsible worker and always take safety measures at the plant seriously, but today is a busy day and you are feeling some pressure to finish your task on time. Despite your best intentions, you make a mistake and accidentally pour large amounts of enriched uranium into the tank without measuring the quantity you are using. Suddenly, an uncontrolled chain reaction occurs, and a large amount of radiation is released into the environment.
This is what happened on September 30, 1999, at a nuclear fuel processing plant in Tokaimura, Japan. Hisashi Ouchi and two colleagues were purifying uranium oxide to manufacture fuel rods for a research reactor.

Ouchi held a funnel while his colleague Masato Shinohara poured a mixture of uranium oxide into a tank. Suddenly, a blue light paralyzed the workers, the first sign that something terrible was about to happen. The workers, inexperienced in handling uranium with that level of enrichment, had poured too much into the tank, leading to a criticality accident.

As a result, an uncontrolled nuclear reaction was triggered, and a large amount of radiation was released.
The three workers were exposed to extremely high levels of radiation, but Ouchi was the most affected due to his proximity to the tank at the time of the explosion. He received a dose of approximately 17 grays.
He suffered burns on 100% of his body and was transferred to a specialized burns hospital.
What effects does a high dose of radiation have on the body?
A high dose of radiation can have serious and potentially deadly effects on the human body. Exposure to high doses of ionizing radiation can damage DNA and body cells, which can result in illnesses and death.
The immediate effects of acute exposure to high doses of radiation can include nausea, vomiting, diarrhea, weakness, fatigue, hair loss, and reddening of the skin. Additionally, exposure to high doses of radiation can affect the internal organs of the body, including the bone marrow, intestines, lungs, heart, and brain.
A criticality accident like the one in this story can generate an even higher dose of radiation than a catastrophic accident at a nuclear plant, such as the reactor explosion in Chernobyl in 1986 in the former Soviet Union, where radiation was dispersed. Nevertheless, 28 people died due to radiation exposure.
In these accidents, a large amount of radiation is released in a short period of time through a burst of neutrons and gamma rays. If you are close enough, you can receive a lethal dose of radiation within seconds.
What happened to Hisashi Ouchi after the accident?

After the accident, Ouchi was quickly transported to a specialized burns hospital, where he received intensive medical treatment to minimize the effects of radiation exposure. He was given intravenous fluids and medications to control his blood pressure and heart rate, and he received a large number of blood cell transfusions to try to stimulate new cell production. Doctors also administered stem cell and platelet injections, and he was given a special diet to increase his protein and calorie levels. Additionally, a skin graft was performed to aid in the healing of his burns.

What happened to his colleagues?
The other two workers involved in the accident, Masato Shinohara and Yutaka Yokokawa, also received doses of radiation, although not as much as Ouchi. They were taken to a hospital for treatment and were eventually discharged after several weeks.
The aftermath effects of the disaster in Tokaimura.
After the nuclear accident in Tokaimura, authorities ordered the 310,000 residents of the village located six miles from the Tokai facility to stay indoors for 24 hours. In the following 10 days, more than 10,000 people were examined to detect radiation exposure, of which over 600 experienced low levels of exposure.

What measures were implemented after the accident?
The accident in Tokaimura led to a thorough review of safety protocols in nuclear plants in Japan and worldwide. It was found that the workers had been using dangerous and inappropriate methods to handle the enriched liquid uranium and had not been adequately trained in nuclear plant safety. The accident prompted significant changes in the regulation and oversight of the nuclear industry in Japan and worldwide.
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