OARAI, Ibaraki Prefecture–Five workers were exposed to radiation on June 6 during an inspection at a nuclear energy research center here, including one with 22,000 becquerels of plutonium in his lungs, the facility’s operator said.
The four other workers had levels of plutonium-239 between 2,200 and 14,000 becquerels in their lungs. All five were also found with as much as 220 becquerels of americium-241.
So far, none of the workers has complained of health problems, according to the Japan Atomic Energy Agency, the often-criticized operator of the Oarai Research and Development Center.
A rough calculation of the 22,000-becquerel figure translates to internal radiation exposure of 1.2 sieverts over one year and 12 sieverts over 50 years. There have been no past examples of such a high level of internal radiation exposure.
However, an agency official said about the worker in his 50s, “The amount is not enough to cause acute radiation damage.”
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Nobuhiko Ban, an NRA commissioner who is a specialist in radiological protection, said at the meeting: “Detection of 22,000 becquerels is a situation that cannot be easily brushed aside. It is no small amount, although it may not be life-threatening. There will be a need to confirm if the work procedures were appropriate.”
The agency said no radioactive materials leaked outside of the center.
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The protective clothing and gloves worn by the five employees were contaminated. Although the workers all wore face masks that covered their mouths and noses, exposure of up to 24 becqerels apparently from plutonium was confirmed in the nasal cavities of three of them.
The five workers were injected with a substance that promotes the discharge of radioactive materials from the body and were transported to the National Institutes for Quantum and Radiological Science and Technology in Chiba Prefecture on June 7.
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