Survey of air dose rate distribution inside and outside of wooden houses in Fukushima Prefecture; Actual condition of dose reduction factor

Kim, M.; Malins, A.*; Machida, Masahiko; Yoshimura, Kazuya; Saito, Kimiaki; Yoshida, Hiroko*

Nihon Genshiryoku Gakkai Wabun Rombunshi (Internet), 22(4), p.156 - 169, 2023/11

https://doi.org/10.3327/taesj.J23.001

Dose reduction factor of a Japanese house is important information in the external exposure estimation of returning residents. In 2019, a total of 19 wooden houses were surveyed in Iitate Village and Namie Town using a gamma plotter that can continuously measure the air dose rate. In addition, the characteristics of the reduction factor were investigated from the measured air dose rate. In the vicinity of houses, uncontaminated areas exist underneath houses and, the ratio of paved surfaces such as asphalt roads is relatively high; furthermore, the pavement has a tendency for the radiation source to decay quickly. Therefore, the air dose rate near the house showed a relatively low value in common at all sites. Air dose rates above unpaved surfaces showed higher values and larger variations than those above paved surfaces within a radius of 50 m form the center of a house. The reduction factor was widely distributed even for one house, if the ratio of every air dose rate observed inside and outside the house is considered. It is suggested that a realistic reduction factor may not be obtained when the reduction factor is obtained based on the measured values at a small number of points that do not have the representativeness of the radiation field to be measured.

R&D of digital technology on inverse estimation of radioactive source distributions and related source countermeasures; R&D status of digital platform including 3D-ADRES-indoor

Machida, Masahiko; Yamada, Susumu; Kim, M.; Okumura, Masahiko; Miyamura, Hiroko; Shikaze, Yoshiaki; Sato, Tomoki*; Numata, Yoshiaki*; Tobita, Yasuhiro*; Yamaguchi, Takashi; et al.

RIST News, (69), p.2 - 18, 2023/09

https://www.rist.or.jp/rnews/69/69s2.pdf

The contamination of radioactive materials leaked from the reactor has resulted in numerous hot spots in the Fukushima Daiichi Nuclear Power Station (1F) building, posing obstacles to its decommissioning. In order to solve this problem, JAEA has conducted research and development of the digital technique for inverse estimation of radiation source distribution and countermeasures against the estimated source in virtual space for two years from 2021 based on the subsidy program "Project of Decommissioning and Contaminated Water Management" performed by the funds from the Ministry of Economy, Trade and Industry. In this article, we introduce the results of the project and the plan of the renewal project started in April 2023. For the former project, we report the derivative method for LASSO method considering the complex structure inside the building and the character of the source and show the result of the inverse estimation using the method in the real reactor building. Moreover, we explain the platform software "3D-ADRES-Indoor" which integrates these achievements. Finally, we introduce the plan of the latter project.

LASSO reconstruction scheme to predict radioactive source distributions inside reactor building rooms; Practical applications

Machida, Masahiko; Shi, W.*; Yamada, Susumu; Miyamura, Hiroko; Yoshida, Toru*; Hasegawa, Yukihiro*; Okamoto, Koji; Aoki, Yuto; Ito, Rintaro; Yamaguchi, Takashi; et al.

Proceedings of Waste Management Symposia 2023 (WM2023) (Internet), 11 Pages, 2023/02

R&D of digital technology on inverse estimation of radioactive source distributions and related source countermeasures; R&D status of digital platform including 3D-ADRES-indoor

Machida, Masahiko; Yamada, Susumu; Kim, M.; Okumura, Masahiko; Miyamura, Hiroko; Malins, A.; Shikaze, Yoshiaki; Sato, Tomoki*; Numata, Yoshiaki*; Tobita, Yasuhiro*; et al.

RIST News, (68), p.3 - 19, 2022/09

https://www.rist.or.jp/rnews/68/68s2.pdf

no abstracts in English

Review of engagement activities to promote awareness of radiation and its associated risk amongst the Japanese public before and after the Fukushima Daiichi Nuclear Power Plant accident

Sakoda, Akihiro; Nomura, Naoki*; Kuroda, Yujiro*; Kono, Takahiko; Naito, Wataru*; Yoshida, Hiroko*

Journal of Radiological Protection, 41(4), p.1258 - 1287, 2021/12

https://doi.org/10.1088/1361-6498/ac2678

Following the Fukushima Daiichi Nuclear Power Plant accident, many radiation experts directly experienced a vast gap between ideal and real public understanding (PU) of radiation in risk communication. Therefore, this study collated and reviewed information about PU activities for radiation and its risk that six Japanese academic societies - which seemed to be socially neutral expert communities - related to radiation and radiation risk conducted before and after the accident. Activities these radiation-related societies provided to general public were discussed from the following perspectives: (1) difficulties in two-way communication due to resources, motivation, public interest and concerns; (2) balance between academic research and PU activities; (3) academic societies' building trust with the public whilst ensuring member experts' neutrality and independence; (4) discussions among academic societies to prepare for public engagement. We hope that this paper encourages experts and academic societies in radiation protection to hold more national and international discussions about their roles in public communication and outreach.

Present status and future perspective of R&D for 3D-ADRES (3-Dimensional Air Dose Rate Evaluation System); Evaluation scheme for air dose rate distributions in city and forest areas towards Fukushima's revitalization

Kim, M.; Malins, A.; Machida, Masahiko; Yoshimura, Kazuya; Saito, Kimiaki; Yoshida, Hiroko*; Yanagi, Hideaki*; Yoshida, Toru*; Hasegawa, Yukihiro*

RIST News, (67), p.3 - 15, 2021/09

https://www.rist.or.jp/rnews/67/ristnews_67.html

no abstracts in English

Examples of practical activities related to public understanding of radiation risk following the Fukushima nuclear accident

Naito, Wataru*; Uesaka, Motoki*; Kuroda, Yujiro*; Kono, Takahiko; Sakoda, Akihiro; Yoshida, Hiroko*

Radioprotection, 55(4), p.297 - 307, 2020/10

https://doi.org/10.1051/radiopro/2020086

After the Fukushima nuclear accident in Japan, a number of practical activities related to public understanding (PU) of radiation risks were implemented inside and outside Fukushima Prefecture. The various noteworthy approaches and strategies behind those practical activities have not been organized and made explicit thus far. In this study, we have organized the noteworthy practical activities related to PU of radiation risks following the Fukushima nuclear accident, and discussed them mainly from the standpoints of communication strategies and approaches. As several examples demonstrate, efforts to contextualize and localize radiation risk in various forms were observed during post-accident recovery in Fukushima, and these efforts were confirmed, through actual experiences, to be an important component of effective PU activities of radiation risks. Community-based or citizen science approaches, such as having affected residents or citizens to measure radioactivity, have contributed to the PU of radiological situations, but some challenges, such as ethical aspects and the handling of uncertainty, have also been revealed. In the era of information and communications technology, a number of citizens, experts, and agencies have made social media a popular platform for disseminating radiation risk messages to the public and have demonstrated that social media can play an important role in providing radiological risk information. The knowledge and lessons learned from the practical activities discussed in this study can be useful in enhancing PU of risks not only radiation but also other stressors such as toxic chemicals, preparing future disasters and supporting risk communication plans during recovery periods after disasters.

Visualization of overlay network using autonomous system relationships

Miyamura, Hiroko; Hu, H.-Y.*; Yoshida, Masahiro*; Ozahata, Satoshi*; Nakao, Akihiro*; Takahashi, Shigeo*

Shingaku Giho, 112(463), p.577 - 582, 2013/03

This report presents a method for visualizing scale-free networks including Overlay networks as an typical example. Visualizing large-scale and complicated networks such as social networks has recently been very popular while conventional network visualization techniques cannot allow us to understand the topological structure of the scale-free networks. This is because the vertex degrees vary at an exponential rate in the scale-free network and thus special attention should be given when visualizing the network connectivity and analyzing the network traffic there. In this report, we employ the hierarchical representation of the scale-free network by referring to their vertex degrees and autonomous system relationships, so that we can clearly visualize the topological structure of the network in 3D space and retrieve the traffic paths over the network.

Analysis of materials about radiation provided to residents after the Fukushima accident and considerations of a method to evaluate; The Efforts of SG1

Kono, Takahiko; Hattori, Takatoshi*; Yokoyama, Sumi*; Nakano, Hironori*; Sato, Noriko*; Kudo, Hiromi*; Nomura, Naoki*; Sakoda, Akihiro; Naito, Wataru*; Kuroda, Yujiro*; et al.

no journal, , 

no abstracts in English

Evaluation of internal exposure to residents due to indoor radiocaesium contamination in residential houses near the FDNPP

Yoshida, Hiroko*; Shinohara, Naohide*; Manabe, Kentaro; Higaki, Shogo*

no journal, , 

no abstracts in English