Immediately after the TEPCO Fukushima Daiichi Nuclear Power Plant accident, it was reported that an eleven-year-old girl in Futaba-cho, Fukushima Prefecture was exposed to an estimated 100 millisieverts of thyroid in the throat. It was found from the documents of the research institute and the Institute of Radiological Medicine (NIRS). One hundred millisieverts have been used in materials such as national data as a guideline for increasing the incidence of cancer due to the effects of radiation. However, the country has so far said, "We have not confirmed a child of 100 millisieverts," and the report was declined. (Takahito Sakakibara)
The document is the “Morning Countermeasures Headquarters Meeting Memorandum” by NIRS on May 2, 2011, two months after the accident. It was published in a request for information disclosure on this paper. According to the report, the actual measurement value of an 11-year-old girl was shown to be "neck (Keibu) 50,000-70,000 cpm (measured by GM)" at the meeting, and "the thyroid equivalent dose was 100 mSv when the intake was 3 days ago. Degree ”.
The thyroid gland is located in neck, and radioactive iodine can easily be collected. A document released by the government and Fukushima Prefecture states that "the risk of cancer is less than 100 millisieverts, which is difficult to detect." "In the Chernobyl accident, cancer develops at over 100 millisieverts."
According to memos and related documents, it was the radiologist of the prefecture staff who measured it. Immediately after the accident, the prefecture examined the radioactive substances on the evacuees' bodies and carried out an inspection to decontaminate them, looking for contamination of my head and clothes. A "GM survey meter" was used as an inspection device. To measure radioactive iodine in the thyroid, a "NaI survey meter", which is easy to check radiation from inside the body, is usually used.
The record was not left unrecorded due to the confusion, but the result was reporeted to Professor Eiichi Honda of the University of Tokushima and the current Associate Professor of Nuclear Fusion Science Institute, Takuya Sase who were staying in Fukushima to support the examinations in April 2011.
Dr. Sase estimated radiation iodine taken into the thyroid gland of the girl as "a dozen kilobecquerels" based on the degree of contamination indicated by the survey meter, and contacted the local NIRS staff. Based on this estimate, it is believed that "100 millisieverts" was reported at the meeting. According to Tokushima University, the engineer said, "When the explosion occurred, the girl said," I was in Futaba (where the nuclear power plant was) playing with friends. "
In late March 2011, the government's Nuclear Emergency Response Headquarters announced that it measured the exposure dose of children under the age of fifteen using NaI, and that it all fell below the standard of 100 millisieverts. However, the target was an area outside the nuclear power plant's thirty kilometers area where evacuation and evacuation were not instructed, and only 1,880 people were examined. At the time of the accident, the girls in Futaba are likely to have missed this measurement.
The NIRS commented that this value was "calculated on the spot based on the information provided at the countermeasures meeting. It has not been examined precisely and has not been published."
<NIRS> Established in 1957 following the 5th Lucky Dragon H-bomb incident. At the time of the Fukushima Daiichi Nuclear Power Plant accident, the national guidelines placed it as the "central institution of the medical system for emergency radiation exposure," which is responsible for detailed dose evaluations, as well as providing advice to relevant institutions and highly specialized treatment. The location is Inage-ku, Chiba.