Three workers may have suffered internal radiation exposure while working in a spent nuclear fuel reprocessing plant in Rokkasho, Aomori Prefecture, Japan Nuclear Fuel has said.
The men in their 20s to 40s are employees of a partner company sent to work in a controlled area of the plant, according to an announcement by Japan Nuclear Fuel on Monday.
Radiation was detected inside the nasal cavity of one of the three, who is in his 40s, prompting the company to check whether all three had been internally exposed.
None of them has reported any change in their health condition so far, Japan Nuclear Fuel said.
According to the company, the three were working to replace filters that remove radioactive materials from gas emitted from a tank, in a building used for denitration of uranium-plutonium mixed solution, when radiation levels rose at around 11:10 a.m. Friday.
After they left the area, as instructed, contamination was found on the outer surface of the filters of their protective masks.
When contamination is detected, workers are typically instructed to cover air intake filters with tape to prevent further contamination and replace the filter while holding their breath.
However, two of the three breathed without filters for up to three minutes, according to Japan Nuclear Fuel. It is not clear when that occurred.
The company is still investigating why the two men breathed without filters. It is also analyzing urine and stool samples from the three workers to determine whether internal radiation exposure occurred, and investigating the cause of the increase in radiation levels.
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