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Story of Miharu in response to the Fukushima Daiichi nuclear power plant accident: The Misho Project

Takeshi Koike, Tohoku University
Monday, November 2, 2015 - 4:00pm to 5:00pm
PAA A-102

A town of Miharu with a population of 18,000 is located directly 45 km west of the crippled Fukushima Daiichi Nuclear Power Plant (FDNPP) in Fukushima prefecture, Japan. The municipal government led an initiative by itself of distributing and administering potassium iodine tablets to its residents who are under 40 years old at 13:00 hrs on March 15, 2011. After all, Miharu has become the sole municipality in Japan to administer the tablets in response to the nuclear accident following the Great East Japan earthquake on March 11, 2011. This action taken by Miharu stirred controversy and was criticized by the Fukushima municipal government as well as some mass media at that time. However, after four years since the disaster, there has been no official assessment by the prefectural or Japanese government on this unique case. Its examination offers invaluable lessons to be incorporated into evacuation procedures and responses in the future nuclear accidents, while the present Japanese administration seeks early resumption of nuclear power plants which have been shut down since the FDNPP accident. In fact, one nuclear power plant has resumed operation as the first reactor to do so since the disaster as of this writing, while a few more plants are expected to follow.

In this colloquium, it will be argued that the timing of ingesting the iodine tablets was indeed appropriate based on the early radiation monitoring conducted independently by one of the residents in the town. According to this measurement, a radioactive plume from FDNPP passed over the town between around 13:30 hrs and 15:30 hrs on March 15, and there was no further major fallout after that. Thus, the Miharu residents who ingested the tablets as advised by the municipal government did so about a half hour prior to the arrival of radioactive 131I. Effectiveness of ingesting the stable iodine lasts for 24 hours, and nearly 100 % of 131I is averted if the tablet is taken prior to or immediately after inhalation of the radionuclide. In addition, an estimated dosage of external exposure to radiation on the school children of the town will be presented.

T Koike et al 2014 J. Radiol. Prot. 34 675 doi:10.1088/0952-4746/34/3/675​

​Watch a video​ of the talk.

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