Tokyo Electric Power Co. said Friday two employees who were working at the crippled Fukushima No. 1 nuclear plant exceeded for the first time the 250-millisievert radiation exposure limit set for the crisis.
The two, who had absorbed high levels of radioactive iodine-131, received a detailed assessment by the National Institute of Radiological Sciences, which said the internal exposure of one worker in his 30s is estimated at 210 to 580 millisieverts and that of the other worker in his 40s is 200 to 570 millisieverts.
Their external radiation exposure is 73 and 88 millisieverts, respectively, meaning the total amount exceeds the 250-millisievert limit.
Tepco spokesman Junichi Matsumoto said the pair have shown no problematic symptoms, and doctors told them they can live just as they normally do, although the long-term prognosis is still unclear.
The two are currently working at the Fukushima No. 2 plant handling tasks that avoid more radiation exposure.
The legal limit for a nuclear plant worker is 50 millisieverts per year under normal circumstances. The emergency limit was 100 millisieverts, then raised to 250 millisieverts, given the crisis. If a human absorbs 500 millisieverts at once, experts say the impact will cause a reduction in the lymphocyte count.
Matsumoto said the reason there are gaps of several hundreds millisieverts in the estimated exposures is because Tepco has yet to pinpoint how the workers absorbed radiation internally.