Three years ago, two employees were exposed to radiation while inspecting an X-ray machine at a Nippon Steel factory in Hyogo Prefecture, and the Nuclear Regulation Authority determined that each employee was exposed to up to 500 milligy of radiation, which is 10 times the annual limit. It was assessed that the incident occurred and was reported to the International Atomic Energy Agency (IAEA).
The regulatory agency has determined that the severity of the accident is ``Level 3'', which indicates a ``serious abnormal event'' according to international standards.
Three years ago, in May 2021, at a Nippon Steel factory in Himeji City, Hyogo Prefecture, two male employees who were inspecting an X-ray device that measures the thickness of products mistakenly found themselves in a room where X-rays were being irradiated. After entering the hospital, he was exposed to radiation, and was subsequently admitted to a facility at Hiroshima University where he received tests and treatment.
According to the Nuclear Regulation Authority, the two suffered skin redness on their arms and faces due to radiation exposure.
Additionally, as a result of investigating the frequency at which abnormal chromosomes occur, it was estimated that one person's exposure dose was 400 to 500 mGy, which is up to 10 times the annual limit, and another person was evaluated to have received less than 100 mGy. The regulatory agency reported its findings to the IAEA last month.
Regarding the seriousness of the accident, the regulatory agency determined that there were non-fatal health effects due to radiation. It is rated as 3.
"Level 3" is considered a "serious abnormal event," and is at the same level as the explosion that occurred at a nuclear fuel reprocessing facility in Tokai Village, Ibaraki Prefecture in 1997. The criticality accident that occurred, in which two people died due to radiation exposure, is classified as "Level 4."
In response to this accident, the Ministry of Health, Labor and Welfare is considering countermeasures.
Expert: ``Major accident: facility managers must ensure safety''
Tomoko Kusama, president emeritus of Oita Prefectural University of Nursing Science who is an expert on radiation protection, said, ``The fact that it has been rated as level 3 can be considered a very serious accident. "There is a possibility that they have received radiation doses. Cases of exposure to that much radiation are rare and have a considerable impact."
He added, ``Radiation is used in a variety of areas. Facility managers must ensure safety, and radiation workers must always keep safety in mind and always think about what they need to protect.'' We have to hit the ground running," he said, stressing the need for regular education and training in addition to equipment measures.