Nearly 40 percent of all Self-Defense Forces personnel, police and firefighters who helped evacuate residents during the Fukushima nuclear crisis in 2011 were exposed to more than a millisievert of radiation — the annual limit for the general public, according to a Cabinet Office study.
Four years after the triple core meltdown, the Cabinet Office surveyed for the first time 2,967 personnel who carried out evacuations within 20 km of the Fukushima No. 1 power plant, as well as decontamination and other related activities from March 12 to 31 that year.
The data were reportedly tallied from dosimeter readings.
The study found that around 62 percent of the personnel were exposed to less than a millisievert and that 38 percent were exposed to a millisievert or more.
Of the latter group, 19 percent received 1 to 2 millisieverts and 5 percent received 5 to 10 millisieverts.
Daily radiation doses remained high until around March 15 — when the third reactor building was hit by a hydrogen explosion — and dropped below 0.1 millisievert from March 18.
The Cabinet Office disclosed the data during a meeting on ways to mitigate radiation exposure for civilians engaged in evacuation procedures during a nuclear accident.
The government is pushing to reactivate the nation’s idled reactors if they clear safety requirements imposed in the wake of the man-made crisis triggered by the earthquake and tsunami on March 11. But public concern persists about whether smooth evacuations are even feasible for nuclear accidents.
The government plans to set a 1-millisievert limit for civilians used in evacuations, such as bus drivers. But some drivers are reluctant to accept the proposal.
While the maximum dose for ordinary people is 1 millisievert per year, the limits for nuclear workers — 100 millisieverts over five years and 50 millisieverts per year in normal times — can be raised in emergencies.