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Chudo, Hiroyuki; Yokoi, Naoto*; Matsuo, Mamoru; Harii, Kazuya*; Suzuki, Jun*; Imai, Masaki; Sato, Masahiro*; Maekawa, Sadamichi*; Saito, Eiji*
Physical Review Letters, 134(13), p.130603_1 - 130603_5, 2025/04
Times Cited Count：0Taniguchi, Takumi; Matsumoto, Saori; Hiraki, Yoshihisa; Sato, Junya; Fujita, Hideki*; Kaneda, Yoshihisa*; Kuroki, Ryoichiro; Osugi, Takeshi
JAEA-Review 2024-059, 20 Pages, 2025/03
JAEA-Review-2024-059.pdf:1.0MB
The basic performance required for solidifying waste into cement, such as fluidity before curing and strength after curing, is expected to be affected by the chemical effects of substances and components contained in the waste. The fluidity before curing and the strength properties after curing are greatly influenced by the curing speed of the cement. We investigated existing knowledge with a focus on chemical substances that affect the curing speed of cement. In this report, chemical substances that affect fluidity are broadly classified into inorganic substances such as (1) anion species, (2) metal elements such as heavy metals, (3) inorganic compounds as cement admixtures, and (4) organic compounds as cement admixtures. Based on the investigation, we actually added chemicals and measured the setting time. As a result, it was found that there are multiple mechanisms contributing to accelerated hardening. We investigated chemical substances that inhibit the curing reaction of cement, and were able to compile information to consider ingredients that are contraindicated in cement curing.
Kokubun, Yuji; Hosomi, Kenji; Nagaoka, Mika; Seya, Natsumi; Inoue, Kazumi; Koike, Yuko; Uchiyama, Rei; Sasaki, Kazuki; Maehara, Yushi; Matsuo, Kazuki; et al.
JAEA-Review 2024-054, 168 Pages, 2025/03
JAEA-Review-2024-054.pdf:2.73MB
The Nuclear Fuel Cycle Engineering Laboratories conducts environmental radiation monitoring around the reprocessing plant in accordance with the "Safety Regulations for Reprocessing Plant of JAEA, Part IV: Environmental Monitoring". This report summarizes the results of environmental radiation monitoring conducted during the period from April 2023 to March 2024 and the results of dose calculations for the surrounding public due to the release of radioactive materials from the plant into the atmosphere and ocean. In the results of the above environmental radiation monitoring, several items were affected by radioactive materials emitted from the accident at the Fukushima Daiichi Nuclear Power Station of Tokyo Electric Power Company, Incorporated (changed to Tokyo Electric Power Holdings, Inc. on April 1, 2016), which occurred in March 2011. In addition, environmental monitoring plan, analysis and measurement methods, monitoring data and their chronological change, meteorological data after statistical processing, status of radioactive waste release and evaluation results of the data over the normal range are included as appendices.
Morishita, Yuki; Miyamura, Hiroko; Sato, Yuki; Matsubara, Jun*; Sumali, B.*; Mitsukura, Yasue*
Nuclear Instruments and Methods in Physics Research A, p.170368_1 - 170368_16, 2025/03
Times Cited Count：0Decommissioning nuclear reactor sites presents challenges due to the presence of various radionuclides, including alpha emitters (e.g., Pu, Am, Cm) and beta emitters (e.g., 
Cs, 
Sr-Y), which pose significant internal exposure risks to workers. Traditional measurement methods require multiple instruments and are time-consuming, particularly in high gamma-ray environments. To address these issues, we developed a remote alpha and beta discrimination measurement system that integrates a stilbene scintillator detector with a silicon photomultiplier, enabling simultaneous detection of both alpha and beta particles. This study further incorporates machine learning techniques, specifically Support Vector Machines (SVM), for automatic discrimination, eliminating the need for user-defined thresholds and ensuring consistent operational conditions. The system was tested with known radiation sources, demonstrating over 96% classification accuracy for alpha and beta particles. Measurements conducted in motion effectively identified contamination sources, confirming the system's capability for real-time analysis. This innovative approach enhances radiation safety and efficiency in nuclear decommissioning operations, making it particularly beneficial in environments where human access is limited.
Arai, Yoichi; Watanabe, So; Nakahara, Masaumi; Funakoshi, Tomomasa; Hoshino, Takanori; Takahatake, Yoko; Sakamoto, Atsushi; Aihara, Haruka; Hasegawa, Kenta; Yoshida, Toshiki; et al.
Progress in Nuclear Science and Technology (Internet), 7, p.168 - 174, 2025/03
The Japan Atomic Energy Agency (JAEA) has been conducting a project named "Systematic Treatment of RAdioactive liquid waste for Decommissioning (STRAD)" project since 2018 for fundamental and practical studies for treating radioactive liquid wastes with complicated compositions. Fundamental studies have been conducted using genuine liquid wastes accumulated in a hot laboratory of the JAEA called the Chemical Processing Facility (CPF), and treatment procedures for all liquid wastes in CPF were successfully designed on the results obtained. As the next phase of the project, new fundamental and practical studies on primarily organic liquid wastes accumulated in different facilities of JAEA are in progress. This paper reviews the representative achievements of the STRAD project and introduces an overview of ongoing studies.
Yamano, Hidemasa; Toyooka, Junichi; Sato, Hiroyuki; Sakaba, Nariaki
Nihon Genshiryoku Gakkai-Shi ATOMO
, 66(12), p.607 - 611, 2024/12
This report mainly introduces trends in fast reactor development in Japan in addition to introducing overseas development trends for major developing countries.
Mochizuki, Akihito; Sato, Toshinori; Wada, Junichi*
JAEA-Research 2024-003, 86 Pages, 2024/06
JAEA-Research-2024-003.pdf:8.13MB
For the geological disposal of high-level radioactive waste, research and studies are being conducted in Japan and abroad to contribute to the mitigation of the upper temperature limit (100
C) in the buffer material assumed in the current disposal system. In this study, uniaxial compression tests under several temperature conditions, some of which exceed 100C, were conducted to understand changes in rock properties under high temperature conditions, using siliceous mudstone (Wakkanai formation) from Horonobe, Hokkaido, as a case study. The uniaxial compressive strength of the rock increased with heating temperature. The uniaxial compressive strength of specimens heated above 100C was comparable to that of specimens desiccated before testing. Mineralogical observations by scanning electron microscopy showed no evidence of alteration of pore structure or minerals, as observed in other rocks in previous studies. In conclusion, the increase in strength of siliceous mudstone with heating temperature observed in this study is considered to be due to the drying of the specimens with heating.
Inaba, Yoshitomo; Sato, Hiroyuki; Sumita, Junya; Ohashi, Hirofumi; Nishihara, Tetsuo; Sakaba, Nariaki
Nihon Kikai Gakkai-Shi, 127(1267), p.25 - 28, 2024/06
Aiming to contribute to net-zero emissions through early social implementation of HTGRs, JAEA promote five projects: HTTR-Heat Application Test, HTGR Domestic Demonstration Reactor, UK HTGR Demonstration Program, UK HTGR Fuel Development Program, and Poland HTGR Research Reactor Basic Design. In addition to these five projects, this article provides an overview of the safety demonstration tests using HTTR.
Sato, Yuki; Kakuto, Takeshi*; Tanaka, Takayuki*; Shimano, Hiroyuki*; Morohashi, Yuko; Hatakeyama, Tomoyoshi*; Nakajima, Junsaku; Ishiyama, Masahiro
Nuclear Instruments and Methods in Physics Research A, 1063, p.169300_1 - 169300_7, 2024/06
Times Cited Count：2 Percentile：63.95(Instruments & Instrumentation)Morito, Makoto*; Fujii, Shun*; Yoshimura, Koki*; Sanada, Yukihisa; Baba, Shoichiro*; Matsunaga, Hiroshi*; Mori, Takami*; Sato, Keiichiro*; Tahara, Junichiro*
Proceedings of 34th International Ocean and Polar Engineering Conference (ISOPE-2024), p.3754 - 3761, 2024/06
This study proposes a method that combines sliding mode control and neural networks as a control method for unmanned surface vehicle to measure radiation in submarine soil. Sliding mode control is used as the base of control input, and corrective inputs are added using a neural network controller so that one of the parameters of sliding mode control, 
, and its rate of change are reduced. After producing a control system using this method, we conducted simulation tests and sea area tests to evaluate whether the survey could be conducted using this method.
Kokubun, Yuji; Nakada, Akira; Seya, Natsumi; Koike, Yuko; Nemoto, Masashi; Tobita, Keiji; Yamada, Ryohei*; Uchiyama, Rei; Yamashita, Daichi; Nagai, Shinji; et al.
JAEA-Review 2023-046, 164 Pages, 2024/03
JAEA-Review-2023-046.pdf:4.2MB
The Nuclear Fuel Cycle Engineering Laboratories conducts environmental radiation monitoring around the reprocessing plant in accordance with the "Safety Regulations for Reprocessing Plant of JAEA, Part IV: Environmental Monitoring". This report summarizes the results of environmental radiation monitoring conducted during the period from April 2022 to March 2023 and the results of dose calculations for the surrounding public due to the release of radioactive materials into the atmosphere and ocean. In the results of the above environmental radiation monitoring, many items were affected by radioactive materials emitted from the accident at the Fukushima Daiichi Nuclear Power Plant of Tokyo Electric Power Company, Incorporated (changed to Tokyo Electric Power Company Holdings, Inc. on April 1, 2016), which occurred in March 2011. Also included as appendices are an overview of the environmental monitoring plan, an overview of measurement methods, measurement results and their changes over time, meteorological statistics results, radioactive waste release status, and an evaluation of the data which deviated of the normal range.
Sato, Yuhi*; Ishizuka, Shigehiro*; Hiradate, Shuntaro*; Atarashi-Andoh, Mariko; Nagano, Hirohiko*; Koarashi, Jun
Environmental Research, 239(Part 1), p.117224_1 - 117224_9, 2023/12
Times Cited Count：3 Percentile：60.44(Environmental Sciences)The stability of soil organic matter (SOM) is important for improving our understanding of the global carbon cycle and ongoing climate change. This study examined the applicability of loss-on-ignition of soil with a stepwise increase in temperature (SIT-LOI) to evaluate the stability of the SOM using soil samples from Japan having different organic matter (OM) and mineral contents and different mean residence times (MRTs), estimated from radiocarbon analysis, for SOM. As the result of this examination, SIT-LOI data was strongly correlated with MRTs. This clearly suggests that SIT-LOI can be an indicator evaluating the stability of SOM in actual environments.
Watanabe, So; Takahatake, Yoko; Ogi, Hiromichi*; Osugi, Takeshi; Taniguchi, Takumi; Sato, Junya; Arai, Tsuyoshi*; Kajinami, Akihiko*
Journal of Nuclear Materials, 585, p.154610_1 - 154610_6, 2023/11
Times Cited Count：0 Percentile：0.00(Materials Science, Multidisciplinary)
OKondo, Yosuke*; Achouri, N. L.*; Al Falou, H.*; Atar, L.*; Aumann, T.*; Baba, Hidetada*; Boretzky, K.*; Caesar, C.*; Calvet, D.*; Chae, H.*; et al.
Nature, 620(7976), p.965 - 970, 2023/08
Times Cited Count：24 Percentile：95.07(Multidisciplinary Sciences)no abstracts in English
Ne at the transition into the island of inversion; Detailed structure study of NeWang, H.*; Yasuda, Masahiro*; Kondo, Yosuke*; Nakamura, Takashi*; Tostevin, J. A.*; Ogata, Kazuyuki*; Otsuka, Takaharu*; Poves, A.*; Shimizu, Noritaka*; Yoshida, Kazuki; et al.
Physics Letters B, 843, p.138038_1 - 138038_9, 2023/08
Times Cited Count：4 Percentile：62.61(Astronomy & Astrophysics)Detailed 
-ray spectroscopy of the exotic neon isotope Ne has been performed using the one-neutron removal reaction from Ne. Based on an analysis of parallel momentum distributions, a level scheme with spin-parity assignments has been constructed for Ne and the negative-parity states are identified for the first time. The measured partial cross sections and momentum distributions reveal a significant intruder p-wave strength providing evidence of the breakdown of the N = 20 and N = 28 shell gaps. Only a weak, possible f-wave strength was observed to bound final states. Large-scale shell-model calculations with different effective interactions do not reproduce the large p-wave and small f-wave strength observed experimentally, indicating an ongoing challenge for a complete theoretical description of the transition into the island of inversion along the Ne isotopic chain.
Harii, Kazuya*; Umeda, Maki; Arisawa, Hiroki*; Hioki, Tomosato*; Sato, Nana; Okayasu, Satoru; Ieda, Junichi
Journal of the Physical Society of Japan, 92(7), p.073701_1 - 073701_4, 2023/07
Times Cited Count：1 Percentile：24.57(Physics, Multidisciplinary)Kodama, Yu*; Katabuchi, Tatsuya*; Rovira Leveroni, G.; Kimura, Atsushi; Nakamura, Shoji; Endo, Shunsuke; Nakano, Hideto*; Sato, Yaoki*; Hori, Junichi*; Shibahara, Yuji*; et al.
EPJ Web of Conferences, 284, p.01024_1 - 01024_3, 2023/05
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)Nakada, Akira; Kanai, Katsuta; Seya, Natsumi; Nishimura, Shusaku; Futagawa, Kazuo; Nemoto, Masashi; Tobita, Keiji; Yamada, Ryohei*; Uchiyama, Rei; Yamashita, Daichi; et al.
JAEA-Review 2022-078, 164 Pages, 2023/03
JAEA-Review-2022-078.pdf:2.64MB
Environmental radiation monitoring around the Tokai Reprocessing Plant has been performed by the Nuclear Fuel Cycle Engineering Laboratories, based on "Safety Regulations for the Reprocessing Plant of Japan Atomic Energy Agency, Chapter IV - Environmental Monitoring". This annual report presents the results of the environmental monitoring and the dose estimation to the hypothetical inhabitant due to the radioactivity discharged from the plant to the atmosphere and the sea during April 2021 to March 2022. In this report, some data include the influence of the accidental release from the Fukushima Daiichi Nuclear Power Station of Tokyo Electric Power Co., Inc. (the trade name was changed to Tokyo Electric Power Company Holdings, Inc. on April 1, 2016) in March 2011. Appendices present comprehensive information, such as monitoring programs, monitoring methods, monitoring results and their trends, meteorological data and discharged radioactive wastes. In addition, the data which were influenced by the accidental release and exceeded the normal range of fluctuation in the monitoring, were evaluated.
Sn nanodotSato, Yuma*; Takeuchi, Yutaro*; Yamane, Yuta*; Yoon, J.-Y.*; Kanai, Shun*; Ieda, Junichi; Ohno, Hideo*; Fukami, Shunsuke*
Applied Physics Letters, 122(12), p.122404_1 - 122404_5, 2023/03
Times Cited Count：5 Percentile：52.19(Physics, Applied)Katabuchi, Tatsuya*; Iwamoto, Osamu; Hori, Junichi*; Kimura, Atsushi; Iwamoto, Nobuyuki; Nakamura, Shoji; Rovira Leveroni, G.; Endo, Shunsuke; Shibahara, Yuji*; Terada, Kazushi*; et al.
EPJ Web of Conferences, 281, p.00014_1 - 00014_4, 2023/03
