著者

Masahiro HOSODA Kazumasa INOUE Mitsuaki OKA Yasutaka OMORI Kazuki IWAOKA Shinji TOKONAMI

出版者

日本保健物理学会

雑誌

保健物理 (ISSN:03676110)

巻号頁・発行日

vol.51, no.1, pp.41-50, 2016 (Released:2016-07-06)

参考文献数

50

被引用文献数

2 25

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Many nuclear facilities are located within Aomori Prefecture, Japan. However, no detailed dose rate distribution map of Aomori Prefecture, including its mountain regions has been reported since the Fukushima Daiichi Nuclear Power Plant accident. A car-borne survey which used a 3-in × 3-in NaI(Tl) scintillation spectrometer was carried out throughout the prefecture for the purposes of making a dose distribution map and estimating the annual external dose. The average absorbed dose rate in air and the annual effective dose were found to be 22 ± 5 nGy h-1 and 0.20 ± 0.08 mSv, respectively. These average values for all of Aomori Prefecture were respectively 44% and 59% of the nationwide average values. The average values with standard deviations of activity concentrations in soil of 40K, 238U and 232Th were 234 ± 148, 15 ± 6, 12 ± 6 Bq kg-1, respectively. The average values of contributions of 40K, 238U and 232Th to absorbed dose rates in air were 39%, 29% and 32%, respectively. The contributions of 134Cs and 137Cs to the absorbed dose rates in air were judged to be negligible.

著者

Yasutaka Omori Hiroaki Wakamatsu Atsuyuki Sorimachi Tetsuo Ishikawa

出版者

福島医学会

雑誌

FUKUSHIMA JOURNAL OF MEDICAL SCIENCE (ISSN:00162590)

巻号頁・発行日

vol.62, no.1, pp.1-17, 2016 (Released:2016-06-08)

参考文献数

49

被引用文献数

1 14

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This study was conducted on the Fukushima Medical University (FMU) premises (in Fukushima City, Fukushima Prefecture) about four years after the Fukushima Daiichi Nuclear Power Plant accident. Its objectives were (1) to create a map of the ambient gamma dose rate (air-kerma rate) distribution, (2) to evaluate the air-kerma rate originating from natural radionuclides, and (3) to investigate the effects of snow cover on changes in the air-kerma rate. This man-borne survey revealed that the air-kerma rate varies widely, ranging from 0.038 μGy h-1 to 0.520 μGy h-1, and is higher on grass than on the other investigated surface types, such as soil, asphalt, and bricks. In this area, the mean air-kerma rate from natural radiation was evaluated to be 0.03 ± 0.01 μGy h-1, which is close to 0.04 μGy h-1, which was measured in central Fukushima City by a local authority.Furthermore, snowfall was found to reduce the air-kerma rate by 5%-30%. This reduction was attributed to attenuation of the primary radiation while passing through the snow cover, and the measured contribution of scattered radiation to the air-kerma rate reduction was small. The reduction rate was found to depend on the initial snow depth but to maintain a similar value for a couple of days, after the snow had partially melted and its depth had decreased. Finally, analysis of the daily dose due to external exposure received on the FMU premises revealed that no further health effects due to chronic radiation exposure at this site are to be expected.