Tokyo Electric Power Co. estimated in spring that about 1,600 workers at the crippled Fukushima No. 1 nuclear power plant would be exposed to radiation exceeding 50 millisieverts during the course of the crisis, an industrial accident prevention body revealed.
Tepco was told to make the projection by the Nuclear and Industrial Safety Agency, which then passed on the information to the Health, Welfare and Labor Ministry.
The health ministry afterward compiled a note for its officials.
The projection was revealed Tuesday by the nonprofit organization Tokyo Occupational Safety and Health Center, which sought disclosure of the note, dated April 25, via a freedom of information request.
For workers engaged in work that would expose them to radiation, the maximum annual level is normally 50 millisieverts, and up to 100 millisieverts in five years. But due to the urgency of the nuclear crisis, that limit was raised to 250 millisieverts for workers at the Fukushima No. 1 plant.
According to the disclosed document, health ministry officials quoted NISA officials as saying the amount of radiation exposure is expected to become “significantly high” for workers at the plant due to the severity of the accident.
NISA officials were also quoted as saying the agency intends to raise the 50-millisievert limit because they need workers exceeding that limit to operate at other nuclear plants as well, the document said.
But NISA officials added that workers who exceed radiation exposure of 100 millisieverts should not engage in operations that would expose them to further radiation for the remaining years of the five-year period, it said.
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