Takeshi Iimoto

The International Nuclear Science Olympiad (INSO) and International Nuclear Science and Technology Academy (INSTA), which are two new networks supported by the IAEA, have begun collaborating on international activities aimed at identifying talented students and nurturing them into a skilled workforce in nuclear science and technology, with a focus on secondary and tertial education levels.

Health, Labour and Welfare of Japan established the Study Group on Radiation Protection Measures for X-ray Equipment. This study group conducted specialized discussions on revising the Regulation on Prevention of Ionizing Radiation Hazards Concerning X-ray Equipment, resulting in a report published on August 30, 2024. The report primarily addresses five key issues:(1) Automatic alarm and safety devices, (2) X-ray supervisors, (3) Specialized education and user training, (4) Application and management of controlled areas, and (5) Support for safety activities conducted by operators and industry associations. This explanatory document summarizes the background and key points of the discussions held during the group actual sites.

The Japanese Journal of Health Physics has published a large number of articles related to the accident at Tokyo Electric Power Company (TEPCO)’s Fukushima Daiichi Nuclear Power Plant in March 2011. Of these, 13 articles on risk communication had been published as of March 2022. The various issues related to risk communication are not limited to radiation and there is no absolute right answer for each case. The articles presented in this journal, which are based on the experiences of experts in the field of radiation protection, may also be seen as a record of the practical issues at the time. Please refer to the original articles.

Background: The Health Physics Society of Japan established a working group to obtain insights and findings from articles related to the Fukushima Daiichi Nuclear Power Station (1F) accident, published in the Japanese Journal of Health Physics.Materials and Methods: This study describes the review results of 47 articles on opinion and others related to the 1F accident in the field other than risk communication, environmental measurement and monitoring, radiation dose measurement and assessment, radiation medicine, and radioactive waste.Results and Discussion: The reviewed articles contain various insights and issues depending on the authors’ standpoints and relevant social interests. As a result, the 1F accident-relevant articles offer various discussion points depending on the authors’ awareness of the issues and their positions, which give an opportunity to make reconsiderations on what kind of academic system health physics or radiation protection should be on the basis of the experiences from the 1F accident.Conclusion: It is crucial for the future development of the Health Physics Society of Japan and relevant academic societies and researchers to address these matters and continue to ask what health physics (or radiation protection) is.

NORMの取扱いの実例と放射線施設等での放射性物質の管理方法を比較し，NORMの合理的な取扱方法の枠組みを考察し提案した。作業区域の考え方として，厳格な管理方針を取る管理区域ではなく，規定を設けない監視区域の考え方を取り入れ，合理的な適用例を示した。作業者とNORM自体の取扱いの枠組みについては，作業者は職業人の特徴を持つが，防護の観点では放射線に関する知識がない等の理由から，公衆として扱うべきとし，管理目標として1～5 mSv/yを提言した。

During the Tokyo Electric Power Company’s Fukushima Daiichi Nuclear Power Station (1F) accident on March 11, 2011, many members of the Japan Health Physics Society, including researchers and radiation workers, were involved in 1F accident-related work. The resulting articles covered a wide range of topics such as lessons learned and future challenges, risk communication, environmental monitoring, dosimetry, radiation medicine, and radioactive waste. In March 2022, a working group was established to review the articles related to the 1F accident published in the Japanese Journal of Health Physics. This article shows the types and number of 1F-related articles published in this journal over a period of about 10 years.

The World Health Organization (WHO) recommends that countries adopt the reference level of 100 Bq m−3 for indoor radon gas. Adopting the reference level requires a preliminary assessment of the indoor radon concentration. In the preliminary investigation, a cut-off value is useful, which is a value for selecting samples that can be reliably determined to be below the reference level (in this paper, the WHO reference level) using a straightforward method. If the true value was the WHO reference level, then the cut-off value of the PicoRad collector for selecting samples was determined as 80 Bq m−3 through the analysis of the 95% prediction interval.

Building materials, such as brick and concrete, are known indoor radon (²²²Rn) and thoron (²²⁰Rn) sources. Most radon and thoron exhalation studies are based on the laboratory testing of pieces and blocks of such materials. To discuss if laboratory findings can be applied to a real-world environment, we conducted intensive in situ exhalation tests on two solid concrete interior walls of an apartment in Japan for over a year. Exhalation rates of radon (J_Rn) and thoron (J_Tn) were measured using an accumulation chamber and dedicated monitors, alongside monitoring indoor air temperature (T) and absolute humidity (AH_in). There were weak correlations between J_Rn or J_Tn and T or AH_in at one tested wall, and moderate correlations of J_Rn and strong correlations of J_Tn with T or AH_in at the other wall, meaning more or less seasonal variations. The findings aligned with previous laboratory experiments on J_Rn but lacked corresponding data for J_Tn. Additionally, a moderate or strong correlation between J_Rn and J_Tn was observed for both tested walls. Comparison with theoretical calculations revealed a new issue regarding the impact of each process of emanation and migration within concrete pores on radon and thoron exhalation. Overall, this study provides insight into parameterizing radon and thoron source inputs in modeling the spatiotemporal dynamics of indoor radon and thoron.