Visual analysis of air dose rate maps

Takahashi, Shigeo*; Sakurai, Daisuke*; Nagao, Fumiya; Kurikami, Hiroshi; Sanada, Yukihisa

Shimyureshon, 42(2), p.68 - 75, 2023/06

This paper introduces a case in which scientific knowledge on understanding the deposition process of radionuclides and evaluating the dose rate reduction due to decontamination work was obtained through visual analysis based on data on the spatio-temporal distribution of air dose rates accumulated through radiation monitoring after the accident. We will discuss the prospects for future efforts to effectively obtain important knowledge that will assist in the planning of policies for reconstruction from the nuclear power plant accident in the future.

Status of study of long-term assessment of transport of radioactive contaminants in the environment of Fukushima (FY2018)

Nagao, Fumiya; Niizato, Tadafumi; Sasaki, Yoshito; Ito, Satomi; Watanabe, Takayoshi; Dohi, Terumi; Nakanishi, Takahiro; Sakuma, Kazuyuki; Hagiwara, Hiroki; Funaki, Hironori; et al.

JAEA-Research 2019-002, 235 Pages, 2019/08

JAEA-Research-2019-002.pdf:21.04MB

The accident of the Fukushima Daiichi Nuclear Power Station (hereinafter referred to 1F), Tokyo Electric Power Company Holdings, Inc. occurred due to the Great East Japan Earthquake, Sanriku offshore earthquake, of 9.0 magnitude and the accompanying tsunami. As a result, large amount of radioactive materials was released into the environment. Under these circumstances, JAEA has been conducting Long-term Environmental Dynamics Research concerning radioactive materials released in environment, especially migration behavior of radioactive cesium since November 2012. This report is a summary of the research results that have been obtained in environmental dynamics research conducted by JAEA in Fukushima Prefecture.

Development of a method of safety assessment for geological disposal considering long-term evolution of geological and topographical environment by uplift and erosion

Wakasugi, Keiichiro; Yamaguchi, Masaaki; Koo, Shigeru*; Nagao, Fumiya; Kato, Tomoko; Suzuki, Yuji*; Ebashi, Takeshi; Umeki, Hiroyuki*; Niibori, Yuichi*

Nihon Genshiryoku Gakkai Wabun Rombunshi, 16(1), p.15 - 33, 2017/03

https://doi.org/10.3327/taesj.J16.010

This study provides a method of safety assessment for the geological disposal of HLW to evaluate the effects of uplift and erosion which are widespread phenomena identified on regional and global scales, and are more or less difficult to avoid in Japan. This method enables to deal with different uplift rate and erosion rate, and to evaluate repository depth, the time required for a repository to reach the weathered zone and surface of the ground, and the number of waste packages eroded as a function of time by using a landform evolution model. Based on trial analysis, the result shows that the maximum dose in the Base Case (uplift rate: 0.3 mm/y) is less than the targeted criterion suggested by the international organization even if the repository reaches the ground surface. Furthermore, the diversifying effect on timing the waste packages to reach to weathered zone due to heterogeneity on altitude of bottom of weathered zone reduces one order magnitude of result of the existed dose assessment. The new method is applicable to evaluate safety of geological disposal based on realistic phenomena of uplift and erosion and to quantify a safety margin and robustness of the disposal system.

Approach for biosphere modeling according to surface environmental conditions

Nagao, Fumiya; Kato, Tomoko; Suzuki, Yuji*; Itazu, Toru*

no journal, , 

The basic matrices were compiled structurally which contain transport and exposure processes in the surface environment. And the method was shown to construct the steady-state biosphere model by combination of the basic matrices. To confirm applicability of the method, a dry run of the biosphere modeling for the hypothetical site was conducted.

Make familiar now and future of the environment in Fukushima; Comprehensive environmental information site

Nagao, Fumiya; Kitamura, Akihiro

no journal, , 

JAEA published new information website in March 2019 about radiocesium in the environment in Fukushima, which named "Fukushima Comprehensive Environmental Information Site". This site aggregates survey data gained by JAEA, results of analytical studies about air dose rate and dynamics of radiocesium, and answers for questions JAEA received.

FaCEIS website of radioactivity database and knowledge

Nagao, Fumiya; Kurikami, Hiroshi; Ito, Satomi; Sawada, Noriyoshi*; Oki, Noriko*

no journal, , 

JAEA is running the website named FaCEIS, in that we arrange the information about environmental radioactivity and air dose rate originated by FDNPP accident. We JAEA provide the information with scientific base to serve the knowledge and safety about Fukushima environment.