|
KMID : 0364920170420010042
|
|
Journal of Radiation Protection and Research
2017 Volume.42 No. 1 p.42 ~ p.47
|
|
|
Reduction of Outdoor and Indoor Ambient Dose Equivalent after Decontamination in the Fukushima Evacuation Zones
|
|
Hiroko Yoshida Ohuchi
Kanagami Takashi
Naitoh Yutaka
Kameyama Mizuki
Hosoda Masahiro
|
|
|
Abstract
|
|
|
Background: One of the most urgent issues following the accident at the Fukushima Daiichi nuclear power plant (FDNPP) was the remediation of the land, in particular, for residential area contaminated by the radioactive materials discharged. In this study, the effect of decontamination on reduction of ambient dose equivalent outdoors and indoors was evaluated. The latter is essential for residents as most individuals spend a large portion of their time indoors.
Materials and Methods: From December 2012 to November 2014, thirty-seven Japanese single-family detached wooden houses were investigated before and after decontamination in evacuation zones. Outdoor and indoor dose measurements (n = 84 and 114, respectively) were collected based on in situ measurements using the NaI (Tl) scintillation surveymeter.
Results and Discussion: The outdoor ambient dose equivalents [H*(10) out ] ranged from 0.61 to 3.71 μSv h -1 and from 0.23 to 1.32 μSv h -1 before and after decontamination, respectively. The indoor ambient dose equivalents [H*(10) in ] ranged from 0.29 to 2.53 μSv h -1 and from 0.16 to 1.22 μSv h -1 before and after decontamination, respectively. The values of reduction efficiency (RE), defined as the ratio by which the radiation dose has been reduced via decontamination, were evaluated as 0.47 ± 0.13, 0.51 ± 0.13, and 0.58 ± 0.08 (average ± σ) when H*(10) out < 1.0 μSv h -1 , 1.0 μSv h -1 < H*(10) out < 2.0 μSv h -1 , and 2.0 μSv h -1 < H*(10) out , respectively, indicating the values of RE increased as H*(10) out increased. It was found that the values of RE were 0.53 ± 0.12 outdoors and 0.41 ± 0.09 indoors, respectively, indicating RE was larger outdoors than indoors.
Conclusion: Indoor dose is essential as most individuals spend a large portion of their time indoors. The difference between outdoors and indoors should be considered carefully in order to estimate residents’ exposure dose before their returning home.
|
|
|
KEYWORD
|
|
|
Decontamination, Reduction efficiency, Outdoors and indoors, Fukushima nuclear exclusion zone
|
|
|
FullTexts / Linksout information
|
|
|
|
|
|
Listed journal information
|
|
|
|