Radiation levels for workers at Kyushu Electric Power Co.’s Sendai nuclear power station are expected to rise five-fold now that the plant’s No. 1 reactor has been restarted.
Documents compiled by the Nuclear Regulation Authority show the average annual radiation dose among workers at the plant in Kagoshima Prefecture were 0.1 and 0.3 millisievert in fiscal 2012 and fiscal 2013, respectively, years in which the plant was inactive.
In fiscal 2004 to fiscal 2011, when the plant’s No. 1 and No. 2 reactors were running, the average annual dose ranged from 0.7 to 1.8 millisieverts.
Meanwhile, the figures show between 1,700 and 4,000 Sendai plant workers were exposed to radiation. Of them, workers from partner companies of Kyushu Electric outnumbered Kyushu Electric employees by 4.7 to 12.4 times.
In the years when reactors were in operation, the average annual radiation dose among workers from partner companies came to 0.7 to 1.9 millisieverts, 3.5 to 13 times the average among Kyushu Electric employees.
In Japan, the maximum permitted cumulative radiation dose in the event of an emergency at a nuclear plant is currently 100 millisieverts.
A cumulative dose of 100 millisieverts is believed to increase the cancer death rate by 0.5 percent.
Many workers at Tokyo Electric Power Co.’s wrecked Fukushima No. 1 nuclear plant exceeded the upper limit following the disaster there in March 2011. In response, the NRA decided to raise the ceiling to 250 millisieverts next April.