Collective exposure dose still remains high at Fukushima Daiichi


The annualized radiation exposure of workers at the Fukushima No. 1 nuclear complex since last March was four times higher than before the triple meltdowns occurred, figures provided by Tokyo Electric Power Co. showed Saturday.

The second such calculation since the power station experienced three catastrophic core meltdowns in March 2011 underscored the difficulties in pursuing long-term decommissioning work and lowering the irradiation of workers at a time when levels of radiation remain sky-high at the crippled facility.

Tepco’s report estimated the total dose workers received from March 2012 to January in “man-sievert” units.

The collective exposure came to 60.1 man-sieverts, or an annualized 65.6 man-sieverts — around 4.4 times higher than the 14.9 man-sieverts recorded at the Fukushima No. 1 power station in fiscal 2009, according to the utility’s calculations.

Compared with the 246.9 man-sieverts logged during the first year of the nuclear crisis from March 2011, the latest figure fell to around a quarter. However, it remained high compared with the average 46.3 man-sieverts logged in fiscal 2011 at other atomic power plants operated by Tepco.

In the period between April 2012 and January, meanwhile, the average exposure of approximately 12,100 workers surveyed at the Fukushima No. 1 plant stood at 4.6 millisieverts, with the highest dose reaching 46.59 millisieverts.

The maximum radiation dose for nuclear workers is set at 50 millisieverts per year, and 100 millisieverts over five years. The government raised the annual limit to 250 millisieverts after the Fukushima No. 1 meltdowns, but lowered it to 50 millisieverts that December.

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