Aerial monitoring around TEPCO's Fukushima Daiichi Nuclear Power Station and development of radiation monitoring technology for unmanned vehicle in fiscal year 2024 (Contract research)

Futemma, Akira; Ochi, Kotaro; Sasaki, Miyuki; Nakama, Shigeo; Kawasaki, Yoshiharu*; Iwai, Takeyuki*; Hiraga, Shogo*; Haginoya, Masashi*; Matsunaga, Yuki*; Yamada, Tsutomu*; et al.

JAEA-Technology 2025-016, 253 Pages, 2026/03

JAEA-Technology-2025-016.pdf:20.16MB

Aerial Radiation Monitoring (ARM) has been used to quickly and widely measure radiation distribution caused by the TEPCO's Fukushima Daiichi Nuclear Power Station (FDNPS) accident resulted from the tsunami accompanying the Pacific coast of Tohoku Earthquake on March 11, 2011. Since the accident, As a commissioned project of the Nuclear Regulation Authority, the Japan Atomic Energy Agency (JAEA) has continuously conducted ARM around FDNPS. This report summarizes the results of the 2024 monitoring activities, evaluates temporal changes in ambient dose rates, and identifies factors contributing to these changes. A terrain-corrected analysis was applied to improve dose rates conversion accuracy, and results with and without this correction were compared. A radon-progeny discrimination method was also used to assess its impact on manned-helicopter measurements. Furthermore, development of unmanned airplane monitoring technologies was advanced to enhance the efficiency of wide-area surveys.

Improvement in legal compliance activities of nuclear security in JAEA

Hirata, Tomohiro; Hanawa, Kazutaka; Shibata, Ryodai; Yamada, Hiroyuki; Yamazaki, Katsuyuki

Dai-46-Kai Nihon Kaku Busshitsu Kanri Gakkai Nenji Taikai Kaigi Rombunshu (Internet), 4 Pages, 2025/12

no abstracts in English

Freeze-crosslinked biomass-based chitosan sponge hydrogels with metal-induced mechanical enhancement for high-performance Cu and Pb adsorption

Nankawa, Takuya; Sugita, Asako; Fukakusa, Chihoko*; Yamada, Teppei*; Sekine, Yurina

Separation and Purification Technology, 378(3), p.134780_1 - 134780_9, 2025/12

https://doi.org/10.1016/j.seppur.2025.134780

We report a sustainable and chemical free strategy to fabricate sponge like chitosan hydrogels via freeze induced physical crosslinking using mild alkaline solutions, without toxic crosslinkers or synthetic additives. The resulting freeze crosslinked biomass-based chitosan sponge hydrogels exhibited interconnected macropores, high water permeability, excellent compressibility, and mechanical recoverability. These features enabled outstanding adsorption of hazardous heavy metals, achieving far better maximum capacities for Cu and Pb markedly surpassing conventional hydrogels. Notably, Cu adsorption induced visible color changes and enhanced mechanical strength, attributed to metal induced secondary crosslinking between amino and hydroxyl groups and adsorbed ions. Cu adsorption also led to a measurable increase in the Youngs modulus of the hydrogels, likely due to coordination with chitosan functional groups.

Development of a phoswich detector for low-energy gamma rays emitted from alpha emitters

Morishita, Yuki; Yamada, Tsutomu*; Nakasone, Takamasa*; Kanno, Marina*; Sasaki, Miyuki; Sanada, Yukihisa; Torii, Tatsuo*

Radiation Measurements, 188, p.107502_1 - 107502_7, 2025/11

https://doi.org/10.1016/j.radmeas.2025.107502

The decommissioning of the Fukushima Daiichi Nuclear Power Station requires thorough inspection of piping for contamination, including alpha nuclides. Since external alpha particle measurements are impractical, detection relies on gamma-rays emitted by the alpha nuclides. Therefore, a phoswich detector for detecting low-energy gamma-rays was developed and experimentally validated. The detector was designed with consideration of energy deposition characteristics and consists of YAP:Ce or HR-GAGG scintillators in combination with BGO scintillators, employing a photomultiplier tube for signal amplification. Validation procedures included Monte Carlo simulations and measurements using actual radiation sources. Both measurement and simulation results demonstrate a correlation in scintillator energy depositions across different gamma-ray energies. Pulse Shape Discrimination (PSD) plots effectively differentiate between low-energy and high-energy gamma-rays, thereby confirming the predictions from simulations. These results suggest promising potential for developing a sensitive low-energy gamma-ray detector utilizing various scintillator combinations. The phoswich detector shows promise for effectively detecting low-energy gamma-rays emitted by alpha nuclides in piping.

Study on the advancement of LWR MOX Fuel; Study on fuel concept for effective Pu utilization and reduction of spent fuel assemblies

Naganuma, Masayuki; Ikusawa, Yoshihisa; Shuji, Yoshiyuki; Suzuki, Kiichi; Yamada, Yoshikazu; Kamiya, Masayoshi

JAEA-Research 2025-006, 165 Pages, 2025/09

JAEA-Research-2025-006.pdf:5.93MB

As a study for advancing LWR MOX fuel, the fuel concept that can contribute to effective plutonium utilization (e.g. reduction of the number of plu-thermal plants required) and reduction of spent fuel subassemblies (interim storage subassemblies) by using existing reactors was investigated. Specifically, since an increase of Pu loading is effective for the above purposes, MOX fuel candidate concepts with the potential to increase Pu loading in the range of the current MOX fuel guidelines (Pu content: 13 wt%, burnup: 45 GWd/t, MOX fuel loading: 1/3) for PWRs were identified and compared in terms of "core and fuel design", "front-end", and "back-end", and the promising fuel concept was selected. Consequently, it was found that placing fuel elements with burnable poisons in the periphery (mainly in the corners) and adjusting the power peaking in the subassembly can increase the Pu content of the fuel elements in the periphery compared to the existing MOX fuel, which is effective in increasing the total Pu loading. Based on this measures, several fuel candidate concepts were devised, then each fuel specification that maintain criticality and power peaking equivalent to the existing MOX fuel were evaluated. As a result of the comparison of the characteristics of each candidate, the fuel concept in which UO-Gd fuel is loaded near the corners was conclusively selected as the most promising concept, because it can increase Pu loading by approximately 15% compared to the existing MOX fuel core and has a lower development burden. Moreover, schematic evaluations were conducted for this fuel concept using the Nuclear Material Balance Analysis Code, confirming the quantitative prospect on how much the above increase in Pu loading would actually affect the number of required plu-thermal plants and the material balance of nuclear fuel cycle.

Development of scientific communication in the field of human factors and ergonomics

Yamada, Yasuyuki*; Ebara, Takeshi*; Oba, Kyoko; Shoji, Naoto*; Toriizuka, Takashi*; Yagi, Eko*; Yoshitake, Ryoji*

Ningen Kogaku, 61(4), p.252 - 261, 2025/08

https://doi.org/10.5100/jje.61.252

This review aims to summarize the human factors and ergonomic understanding of science communication and to present future perspectives, based on discussions within the Science Communication Research Committee of the Japan Human Factors and Ergonomics Society. It first reviewed the definitions, trends, and approaches to science communication, and introduced practices in the field of human factors and ergonomics (HFE) based on its various types. It then discussed the roles of science communication in the context of risk management, outlined key considerations for effective interventions, presented HFE approaches tailored to participants' human traits, and identified the competencies required of science communicators. Finally, it summarized issues for practice and research, and proposed directions for advancing science communication within the domain of HFE. We hope this review contributes to a shared understanding of science communication in HFE and serves as a foundation for its future development.

Effect of potassium doping on the electrical properties of stacked graphene layers

Yamada, Takatoshi*; Ogawa, Shuichi*; Yoshigoe, Akitaka; Tsuda, Yasutaka; Masuzawa, Tomoaki*; Okada, Mitsuhiro*; Kobashi, Kazufumi*; Okigawa, Yuki*

Japanese Journal of Applied Physics, 64(7), p.07SP17_1 - 07SP17_5, 2025/07

https://doi.org/10.35848/1347-4065/aded98

Linking combustion-derived magnetite and black carbon; Insights from magnetic characterization of PM in downwind East Asia

Nozomu, Tsuchiya*; Ikemori, Fumikazu*; Kawasaki, Kazuo*; Yamada, Rena*; Hata, Mitsuhiko*; Furuuchi, Masami*; Iwamoto, Yoko*; Kaneyasu, Naoki*; Sadanaga, Yasuhiro*; Watanabe, Takahiro; et al.

Environmental Science & Technology, 59(21), p.10400 - 10410, 2025/05

https://doi.org/10.1021/acs.est.4c14187

Black carbon (BC) is a typical primary aerosol emitted from combustion. While its co-existence with iron oxides (FeO) has recently been reported, the extent of bias caused by FeO mixing to the BC observations is largely unknown. To identify the dominant FeO emission sources and associated overestimation of BC, magnetics properties of PM collected at a remote site in East Asia was investigated in combination with detailed isotopic and chemical analyses. Consequently, biomass burning events did not enhance aerosol magnetism as they did for the mass concentration of BC, whereas coal burning events coincided with periods of high magnetization. Therefore, magnetization/BC ratio is proposed as a highly selective indicator for identifying combustion sources (i.e. coal, oil or biomass burning).

Environmental radiation monitoring data from 10 years after the accident at the Fukushima Daiichi Nuclear Power Station, conducted by Oarai Nuclear Engineering Institute, JAEA

Inoue, Yuki; Yamada, Junya; Hamaguchi, Takumi; Seya, Natsumi; Muto, Yasunobu; Nohara, Naofumi; Oishi, Tetsuya; Hashimoto, Makoto

JAEA-Data/Code 2024-017, 109 Pages, 2025/03

JAEA-Data-Code-2024-017.pdf:4.54MB

This report presents the results of environmental radiation monitoring at Oarai Nuclear Engineering Institute, JAEA for 10 years from 2011 to 2021 after the accident at the Fukushima Daiichi Nuclear Power Station. Database of monitoring results are included as an appendix. Environmental transfer parameters, deposition velocity, resuspension factor, concentration factor and distribution coefficient, are calculated as an Appendix.

Assessment of individual external exposure doses based on environmental radiation in areas affected by the Fukushima Daiichi Nuclear Power Station accident

Sato, Rina; Yoshimura, Kazuya; Sanada, Yukihisa; Mikami, Satoshi; Yamada, Tsutomu*; Nakasone, Takamasa*; Kanaizuka, Seiichi*; Sato, Tetsuro*; Mori, Tsubasa*; Takagi, Marie*

Environment International, 194, p.109148_1 - 109148_8, 2024/12

https://doi.org/10.1016/j.envint.2024.109148

Assessment of individual external doses from ambient dose equivalents is used for predictive and retrospective assessments where personal dosimeters are not applicable. However, it tends to contain more errors than assessment by personal dosimetry due to various parameters. Therefore, in order to accurately assess the individual dose from ambient dose equivalents, a model that estimates effective doses considering life patterns and the shielding effects by buildings and vehicles, were developed in this study. The model parameters were examined using robust datasets of environmental radiation measured in the areas affected by the Fukushima Daiichi Nuclear Power Station accident in 2020 to 2021. The accuracy of the model was validated by comparison with 106 daily personal doses measured in Fukushima Prefecture in 2020. The measured personal dose was well reproduced by the model-estimated effective dose, showing that the model can be used to assess the individual exposure dose, similar to personal dosimetry. Furthermore, this model is an effective tool for radiation protection, as it can estimate the individual dose predictively and retrospectively by using environmental radiation data.