방사선방호 및 안전

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  • [Health Phys.] Reassessment of Internal Thyroid Doses to 1,080 Children Examined in a Screening Survey after the 2011 Fukushima Nuclear Disaster.2011 후쿠시마 방사능재난 후 스크리닝 조사에 따른 1,080명 어린이의 갑상선 내부피폭선량 재평가

    National Institutes for Quantum and Radiological Science and Technology / 김은주, Osamu Kurihara*

  • 출처
    Health Phys.
  • 등재일
    2020 Jan
  • 저널이슈번호
    118(1):36-52. doi: 10.1097/HP.0000000000001125.
  • 내용

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    Abstract
    The dose reconstruction of populations potentially affected by the accident at the Fukushima Daiichi nuclear power plant in March 2011 is of great importance. However, it has been difficult to assess internal thyroid doses to Fukushima residents (mainly from their intake of I) due to the lack of direct measurements. For the residents, only about 1,300 data points related to I are available, and 1,080 of the data points were obtained from the screening campaign that was conducted by the Nuclear Emergency Response Local Headquarters at the end of March 2011 in Kawamata Town, Iwaki City, and Iitate Village. Here, we reassessed thyroid doses to 1,080 subjects aged ≤15 y old using new age-specific conversion factors to determine I thyroid contents from net signals of the devices used, with consideration for the possible uncertainty related to the measurements. The results demonstrated that thyroid equivalent doses to the subjects were <30 mSv (excluding outliers). We also demonstrate dose distributions of each age group from the above three municipalities and those of subjects from Minamisoma City and Fukushima City. One of the findings was that the I intake was similar among different age groups in each of the three municipalities. This was consistent with the assumption that ingestion was a dominant route of intake rather than inhalation. The range of thyroid doses to Iitate Village residents was similar to that to Iwaki City residents even though the I concentration in tap water was much higher in Iitate Village than Iwaki City. The range of thyroid doses to Minamisoma City residents was similar to that to Iitate Village and Iwaki City residents, and the range for Fukushima City residents was smallest among the five municipalities. Since the major route of intake has remained unclear, this paper presents the plausible upper and lower thyroid doses, between which the actual doses are thought to mostly exist, based on two intake scenarios: single inhalation and repeated ingestion. Further research is thus necessary to extract useful evidence from the individual evacuation behaviors for improving the present internal thyroid dose assessment.

     


    Author information

    Kim E1, Yajima K1, Hashimoto S1, Tani K1, Igarashi Y1,2, Iimoto T2, Ishigure N1, Tatsuzaki H1, Akashi M1, Kurihara O1.
    1
    National Institutes for Quantum and Radiological Science and Technology, Chiba, Japan.
    2
    University of Tokyo, Chiba, Japan.

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