title: Reduction factors for wooden houses due to external γ-radiation based on in situ measurements after the Fukushima nuclear accident.
abstract: For estimation of residents' exposure dose after a nuclear accident, the reduction factor, which is the ratio of the indoor dose to the outdoor dose is essential, as most individuals spend a large portion of their time indoors. After the Fukushima nuclear accident, we evaluated the median reduction factor with an interquartile range of 0.43 (0.34-0.53) based on 522 survey results for 69 detached wooden houses in two evacuation zones, Iitate village and Odaka district. The results indicated no statistically significant difference in the median reduction factor to the representative value of 0.4 given in the International Atomic Energy Agency (IAEA)-TECDOC-225 and 1162. However, with regard to the representative range of the reduction factor, we recommend the wider range of 0.2 to 0.7 or at least 0.2 to 0.6, which covered 87.7% and 80.7% of the data, respectively, rather than 0.2 to 0.5 given in the IAEA document, which covered only 66.5% of the data. We found that the location of the room within the house and area topography, and the use of cement roof tiles had the greatest influence on the reduction factor.
authors.affiliation: Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aramaki-Aoba, Aoba-ku, Sendai, Miyagi 980-8578, Japan.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Yoshida-Ohuchi
authors.affiliation: Department of Radiological Life Sciences, Hirosaki University Graduate School of Health Sciences, 66-1 Hon-cho, Hirosaki, Aomori 036-8564, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Hosoda
authors.affiliation: Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aramaki-Aoba, Aoba-ku, Sendai, Miyagi 980-8578, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Kanagami
authors.affiliation: Japan Environment Research Co., Ltd., 2-15-1 Hon-cho, Aoba-ku, Sendai, Miyagi 980-0014, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Uegaki
authors.affiliation: Japan Environment Research Co., Ltd., 2-15-1 Hon-cho, Aoba-ku, Sendai, Miyagi 980-0014, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Tashima
mesh_terms: D000328:Adult; D062406:Fukushima Nuclear Accident; D005720:Gamma Rays / Q000009:adverse effects*; D006801:Humans; D055848:Nuclear Power Plants / Q000706:statistics & numerical data; D011829:Radiation Dosage; D011834:Radiation Monitoring / Q000706:statistics & numerical data*; D011835:Radiation Protection / Q000706:statistics & numerical data*; D018788:Radioactive Hazard Release / Q000706:statistics & numerical data*; D014934:Wood