Summary of temporal changes in air dose rates and radionuclide deposition densities in the 80 km zone over five years after the Fukushima Nuclear Power Plant accident

Saitô, Kimiaki; Mikami, Shuichi; Andoh, Masaki; Matsuda, Norihiro; Kinase, Sakae; Tsuda, Shuichi; Yoshida, Tadayoshi; Sato, Tetsuro; Seki, Atsushi; Yamamoto, Hideaki; Sanada, Yukihisa; Wainwright, Haruko M.; Takemiya, Hiroshi

doi:10.1016/j.jenvrad.2018.12.020

Cited by 55 publications

(57 citation statements)

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“…In August 2016, the air dose rate decreased to < 40% of that in June 2011 by physical decay. The air dose rate in undisturbed fields decreased to about a half of that expected from radioactive decay, and the air dose rate above roads measured by car-borne survey decrease to one-third [34]. Figure 7 is useful to understand general decreasing tendencies in air dose rate.…”

Section: Jrprmentioning

confidence: 99%

“…These tendencies are explained by radio- Temporal changes in average air dose rates evaluated by using data from car-borne surveys, fixed-location measurements in undisturbed fields, helicopter surveys, and walk surveys. Air dose rates were normalized to those in June 2011 [34].…”

Section: Temporal Change In Radiological Environments 1 Air Dose Ratementioning

confidence: 99%

“…Concerning administrative division, it was estimated that 80% of the radiocesium was deposited in Fukushima Prefecture and the rest was spread across Gunma, Tochigi, Ibaraki, and Miyagi Prefectures. Figure 6 shows the air dose rate distribution maps for different years after the accident constructed by a simple integration of helicopter-survey data and fixed-location measurement data [34]. Air dose rates have decreased greatly since the accident.…”

mentioning

confidence: 99%

“…Average air dose rate by different monitoring methods had different decreasing tendencies, because each monitoring method targeted a different environmental situation. Figure 7 shows the decreasing tendencies of average air dose rates within the 80 km zone measured from fixed-location measurements, car-borne surveys, walk surveys, and helicopter surveys, together with the air dose rate reduction expected from the physical decay [24,[34][35][36]. The dose rates were normalized to that in June 2011.…”

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confidence: 99%

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Temporal Change in Radiological Environments on Land after the Fukushima Daiichi Nuclear Power Plant Accident

et al. 2019

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Massive environmental monitoring has been conducted continuously since the Fukushima Daiichi Nuclear Power accident in March of 2011 by different monitoring methods that have different features together with migration studies of radiocesium in diverse environments. These results have clarified the characteristics of radiological environments and their temporal change around the Fukushima site. At three months after the accident, multiple radionuclides including radiostrontium and plutonium were detected in many locations; and it was confirmed that radiocesium was most important from the viewpoint of long-term exposure. Radiation levels around the Fukushima site have decreased greatly over time. The decreasing trend was found to change variously according to local conditions. The air dose rates in environments related to human living have decreased faster than expected from radioactive decay by a factor of 2-3 on average; those in pure forest have decreased more closely to physical decay. The main causes of air dose rate reduction were judged to be radioactive decay, movement of radiocesium in vertical and horizontal directions, and decontamination. Land-use categories and human activities have significantly affected the reduction tendency. Difference in the air dose rate reduction trends can be explained qualitatively according to the knowledge obtained in radiocesium migration studies; whereas, the quantitative explanation for individual sites is an important future challenge. The ecological half-lives of air dose rates have been evaluated by several researchers, and a short-term half-life within 1 year was commonly observed in the studies. An empirical model for predicting air dose rate distribution was developed based on statistical analysis of an extensive car-borne survey dataset, which enabled the prediction with confidence intervals. Different types of contamination maps were integrated to better quantify the spatial data. The obtained data were used for extended studies such as for identifying the main reactor that caused the contamination of arbitrary regions and developing standard procedures for environmental measurement and sampling. Annual external exposure doses for residents who intended to return to their homes were estimated as within a few millisieverts. Different forms of environmental data and knowledge have been provided for wide spectrum of people. Diverse aspects of lessons learned from the Fukushima accident, including practical ones, must be passed on to future generations.

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Section: Jrprmentioning

confidence: 99%

Section: Temporal Change In Radiological Environments 1 Air Dose Ratementioning

confidence: 99%

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Temporal Change in Radiological Environments on Land after the Fukushima Daiichi Nuclear Power Plant Accident

et al. 2019

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“…Due to the carry-over of radioactive substances into the ocean, just 2 PBqs of 137 Cs and 134 Cs fell to the territory of East Japan, which is 20-30 times less than the Chernobyl fallout in Europe. 10) The retrospective assessment 2011, was given at the highest level 7 of 7 INES levels. 7) The population was irradiated with radioactive plumes and fallouts from the Fukushima-1 NPP accident from March 12, 2011, along all the exposure pathways described in Section 2 for aerial release.…”

Section: Core Melting Of Three Reactors At Fukushima-1 Npp Japanmentioning

confidence: 99%