Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Kawaguchi, Munemichi*; Ikeda, Asuka; Saito, Junichi
Annals of Nuclear Energy, 226, p.111880_1 - 111880_9, 2026/02
Times Cited Count：0
underwater radiation monitoring detectorJi, W.*; Lee, E.*; Ji, Y.-Y.*; Ochi, Kotaro; Yoshimura, Kazuya; Funaki, Hironori; Sanada, Yukihisa
Nuclear Engineering and Technology, 58(2), p.103933_1 - 103933_6, 2026/02
We aimed to validate the performance of an in situ underwater radiation detector, MARK-U1 (Monitoring of Ambient Radiation of KAERI - Underwater), was used to estimate 
Cs activity concentration in river and reservoir sediment at predicted sites of contamination. Additionally, underwater core samples were collected to measure the radioactivity using a high-purity germanium (HPGe) detector. To estimate radioactivity, a conversion factor was derived by comparing the measured spectrum and Cs activity in the sample. A Monte Carlo N-Particle (MCNP) simulation was conducted to determine the effective source geometry for in situ measurement. The simulation results correlated well with the on-site MARK-U1 monitoring results, with a deviation of 31.62%. These findings validate the performance of the in situ detector. This device can therefore be used to estimate Cs activity concentration in the underwater sediment via on-site monitoring, without requiring sample collection.
Qin, T. Y.*; Hu, F. F.*; Xu, P. G.; Zhang, R.*; Su, Y. H.; Ao, N.*; Li, Z. W.*; Shinohara, Takenao; Shobu, Takahisa; Wu, S. C.*
International Journal of Fatigue, 202, p.109233_1 - 109233_16, 2026/01
Chong, Y.*; Tsuru, Tomohito; Gholizadeh, R.*; Minor, A. M.*; Tsuji, Nobuhiro*
Acta Materialia, 301, p.121523_1 - 121523_12, 2025/12
Twinning is essential for achieving large ductility in hexagonal close-packed (HCP) titanium alloys that inherently lack independent slip systems due to an asymmetrical HCP crystal structure. Unfortunately, twinning is in principle suppressed by a trace amount of interstitial oxygen, resulting in a substantially deteriorated ductility in titanium. However, the underlying mechanism remains in dispute so far. Here, we report a systematic multiscale study on the twinning/detwinning behaviors of Ti-O alloys that provides a clear mechanistic view of how interstitial oxygen inhibits twinning. We reveal for the first time that oxygen atoms segregate to both {10
2}
2} compression twin boundaries using atom probe tomography. Combined with theoretical simulations that unravel a strong pinning effect of oxygen atoms on twin boundary due to an oxygen shuffling mechanism, we explain the distinctive migration abilities of twin boundaries in Ti-O alloys at different temperatures. The insights from our experimental and computational work provide a rationale for the design of titanium alloys with increased tolerance to variations in interstitial impurity content, with significant implications for more widespread use of this high strength, light weight material.
Dechenaux, B.*; Brovchenko, M.*; Araki, Shohei; Gunji, Satoshi; Suyama, Kenya
Annals of Nuclear Energy, 223, p.111555_1 - 111555_11, 2025/12
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)Ji, Y.-Y.*; Joung, S.*; Ji, W.*; Ochi, Kotaro; Sasaki, Miyuki; Sanada, Yukihisa
Journal of Radiological Protection, 45(4), p.042501_1 - 042501_11, 2025/12
This study reports the development and field validation of KAERI's UAV-based gamma-ray spectrometry system equipped with LaBr
(Ce) detectors. Joint surveys with JAEA near Fukushima Daiichi Nuclear Power Plant (FDNPP) showed reliable dose rate estimation after applying altitude based attenuation correction, through discrepancies occurred in sloped terrain. Incorporating terrain data is recommended to enhance accuracy for emergency response applications.
Yoshikawa, Masanori; Seki, Akiyuki*; Okita, Shoichiro; Takaya, Shigeru; Yan, X.
Nuclear Engineering and Design, 444, p.114350_1 - 114350_9, 2025/12
Times Cited Count：0 Percentile：0.00Ota, Akira*; Ito, Sho*; Sonobe, Hideaki*; Ino, Susumu*; Choi, B.; Nishida, Akemi; Shiomi, Tadahiko
Nuclear Engineering and Design, 444, p.114403_1 - 114403_7, 2025/12
Times Cited Count：0no abstracts in English
Morishita, Yuki; Nakama, Shigeo; Ochi, Kotaro; Urabe, Yoshimi*; Kanno, Marina*
Radiation Measurements, 189, p.107513_1 - 107513_6, 2025/12
Following the Fukushima Daiichi Nuclear Power Plant accident, radioactive cesium contamination posed a significant environmental concern. This study developed a compact gamma-ray spectrometer utilizing a Ce:GPS scintillator and a compact photomultiplier tube (PMT) for environmental monitoring. The spectrometer was designed to overcome limitations of traditional NaI(Tl) detectors, leveraging the non-hygroscopic nature and high energy resolution of Ce:GPS scintillators. Performance was evaluated through measurements of a Cs source and comparison with a commercial NaI(Tl) survey meter. The spectrometer's potential for effective and portable monitoring of radioactive cesium in contaminated environments was demonstrated. The system was tested using sealed sources, confirming its ability to detect the 662 keV photopeak of Cs with high accuracy. Field measurements in radiocesium-contaminated areas showed the spectrometer's effectiveness in detecting dose rate variations and high-dose hotspots. This portable, durable spectrometer shows promise for applications in environmental radiation monitoring and remote sensing technologies.
Dei, Shuntaro; Shibata, Masahito*; Negishi, Kumi*; Sugiura, Yuki; Amano, Yuki; Bateman, K.*; Wilson, J.*; Yokoyama, Tatsunori; Kagami, Saya; Takeda, Masaki; et al.
Results in Earth Sciences (Internet), 3, p.100097_1 - 100097_16, 2025/12
Interactions between cement and host rock in geological repositories for radioactive waste will result in a chemically disturbed zone, which may potentially affect the long-term safety. This paper investigates the chemical evolution at the interface between cement (Ordinary Portland Cement: OPC and Low Alkaline Cement: LAC) and mudstone after 11 years of in situ reactions at the Horonobe Underground Research Laboratory. The study combines various analytical techniques to identify the key reactions at the cement-rock interface, including cement dissolution, precipitation of secondary minerals such as calcite and C-(A-)S-H phases, cation exchange in montmorillonite and reduced porosity in mudstone. The study also highlights the effects of cement-mudstone interactions on radionuclide migration, such as reduction of diffusivity due to reduced porosity and enhancement of sorption due to incorporation into secondary minerals in the altered mudstone.
and Pb adsorptionNankawa, Takuya; Sugita, Asako; Fukakusa, Chihoko*; Yamada, Teppei*; Sekine, Yurina
Separation and Purification Technology, 378(3), p.134780_1 - 134780_9, 2025/12
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.
Asahi, Miyako; Hozumi, Shinsei; Suzuki, Ichiro; Seya, Manato; Mori, Masakazu; Sakamoto, Yu; Kinoshita, Junichi; Sudo, Tomoyuki
JAEA-Testing 2025-005, 15 Pages, 2025/11
JAEA-Testing-2025-005.pdf:1.37MB
Radioactive wastes generated from the nuclear facilities of the Nuclear Science Research Institute is collected at Radioactive Waste Treatment Facilities, where it is treated or stored according to its radioactivity level and properties. Radioactive Waste Treatment Facilities is composed of several buildings, of which Waste Treatment Facility No.1 has the incinerator, and Waste Treatment Facility No.2 has the equipment treating solid waste in concrete cells. Since Waste Treatment Facility No.1 and No.2 were built more than 40 years ago, the carbonation test was conducted in FY2024 to consider future maintenance management. In addition, the progress of carbonation was predicted based on the test results. This report describes an overview of the carbonation test and the prediction of the progress of carbonation.
Collaborative Laboratories for Advanced Decommissioning Science; Institute of Science Tokyo*
JAEA-Review 2025-026, 72 Pages, 2025/11
JAEA-Review-2025-026.pdf:7.97MB
The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") in FY2023. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2022, this report summarizes the research results of the "Investigation of effects of nano interfacial phenomena on dissolution aggregation of alpha nanoparticles by using micro nano technologies" conducted in FY2023. To ensure the safety of retrieval and storage management of nuclear fuel debris generated by the Fukushima-Daiichi Nuclear Power Station accident, understanding of dissolution-denaturation behavior of the fuel debris alpha particles is one of the most crucial issues. This research aims to create novel microfluidic real-time measurement device for elucidating dissolution, aggregation, and denaturation processes of metal oxide nanoparticles under various solution environments, and clarify their nano-size and interfacial effects. In this year, we conducted bulk and micro dissolution tests of simulated fuel debris particles (UO
mechanical-treated nanoparticles, UO chemical-treated nanoparticles, and (U,Zr)O nanoparticles), and successfully clarified that the effects of particle sizes, reaction times, and HO concentrations on the dissolution behavior of each nanoparticle. In particular, it was found that (U,Zr)O nanoparticles have different degrees of Zr catalytic reactions depending on HO concentrations, resulting in the generation of different amounts of gas and U. Moreover, we developed a new microfluidic device which enables to instantly react the nanoparticles with HO solutions, and determined dynamic aggregation and dissolution rates of the nanoparticles. The research was carried out in close collaboration with UK researchers, and achieved the expected goal of this year.
Irisawa, Eriko; Kato, Chiaki
Corrosion Science, 256, p.113173_1 - 113173_16, 2025/11
Times Cited Count：0 Percentile：0.00(Materials Science, Multidisciplinary)Nguyen, T. H. T.; Sanami, Toshiya*; Yamazaki, Hirohito*; Iwamoto, Nobuyuki; Itoga, Toshiro*; Kirihara, Yoichi; Lee, E.*; Sugihara, Kenta*; Miyamoto, Shuji*; Hashimoto, Satoshi*; et al.
Physics Letters B, 870, p.139900_1 - 139900_8, 2025/11
Kimura, Yoshiki; Yamaguchi, Tomoki
Radioisotopes, 74(3), p.251 - 264, 2025/11
Radioisotope identification (RIID) by gamma-ray spectral analysis has been widely used, and accurate identification of radioisotopes is an important issue in various fields. Handheld instruments are commonly used for on-site RIID but often suffer from limited performance. This paper proposes a spectral deconvolution using unsupervised neural network models for RIID with handheld instruments in field use. This approach allows optimization of the neural network for deconvolution based on a measured spectrum combined with an energy-broadening matrix, and it does not require extensive training datasets or the precise modeling of the detector and measurement conditions. The performance of the proposed approach was examined in simulated and measured spectra, assuming the measurements of several radioisotopes with CsI(Tl) spectrometers. It was demonstrated that the unsupervised neural network models can improve the peak resolution more significantly compared to conventional deconvolution algorithms and contribute to RIID performance in the low energy resolution spectra.
Yamaguchi, Masatake; Ebihara, Kenichi; Itakura, Mitsuhiro
Scripta Materialia, 268, p.116887_1 - 116887_6, 2025/11
Times Cited Count：0 Percentile：0.00Matsunaga, Keita*; Aizawa, Koki*; Asamori, Koichi; Ogawa, Hiroki*; Utsugi, Mitsuru*; Yoshimura, Ryokei*; Yamazaki, Kenichi*; Uchida, Kazunari*; Matsushima, Takeshi*; Inoue, Tomohiro*; et al.
Tectonophysics, 915, p.230880_1 - 230880_11, 2025/11
Risk Analysis Research Group, Nuclear Safety Research Center
JAEA-Testing 2025-004, 75 Pages, 2025/10
JAEA-Testing-2025-004.pdf:3.13MB
When a nuclear emergency occurs at a nuclear power plant (NPP), protective actions such as evacuation and sheltering are implemented to reduce radiation exposures to the public around the vicinity areas of the NPP. The necessity of the protective actions should be judged, taking into account the various types of information from the on-site and the off-site with reflecting the drastically change of accident situation. Japan Atomic Energy Agency has developed EXTREME (EXpert support Tool for Responding to a nuclear EMErgency) to enable quick and consistent assessments for supporting decision-makers during the response phase after a nuclear emergency occurred. The tool implements simplified models for assessing accident progression, environmental transport, and radiation doses to the public. This tool is also available as a PC-based graphical user interface (GUI) for easy operation by users. This report describes the usage of the developed support tool, focusing on the GUI configuration and the flow of calculations. It is expected that this support tool will effectively assist decision-makers in making judgments and decisions regarding protective actions during the response phase in a nuclear emergency.
Ouchi, Takuya; Nagata, Hiroshi; Shinoda, Yuya; Yoshida, Hayato; Inoue, Shuichi; Chinone, Marina; Abe, Kazuyuki; Ide, Hiroshi; Watahiki, Shunsuke
JAEA-Technology 2025-006, 25 Pages, 2025/10
JAEA-Technology-2025-006.pdf:1.59MB
In the future, radioactive waste which generated from nuclear research facilities in Japan Atomic Energy Agency are planning to be buried for the near surface disposal. It is necessary to establish the method to evaluate the radioactivity concentrations of the radioactive wastes. Therefore, at the Oarai Nuclear Engineering Institute, in order to contribute to the study of methods for evaluating radioactivity concentrations of the radioactive wastes from nuclear research facilities, samples were taken from radioactive waste that are expected to be buried in the future and radiochemical analysis is used to obtain data on the radioactivity concentration of each nuclide contained in the radioactive waste. This report presents the concept of selecting sample collection targets and summarizes the sampling of radioactive materials conducted at the JMTR reactor facility in fiscal years 2023 and 2024 to obtain data on radioactivity concentrations.
