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Collaborative Laboratories for Advanced Decommissioning Science; Institute of Science Tokyo*
JAEA-Review 2026-007, 65 Pages, 2026/06
JAEA-Review-2026-007.pdf:4.67MB
The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), has been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") from FY2019. 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 FY2024, this report summarizes the research results of the "Development of a laser deflection-type ultrasonic wideband 3D imaging system for in-vessel visualization in high-radiation and non-visible environments" conducted in FY2024. The present study aims to maximize the safety of debris-cutting operations by enabling visualization of in-vessel structures, fuel debris shapes, and scattered particles at distances on the order of several meters, even under dusty and turbid water conditions during work. To achieve this, a compact and portable ultrasonic device suitable for mounting on robots and manipulator arms is employed to develop a laser deflection-type ultrasonic wideband 3D imaging system. In FY2024, the project carried out imaging performance evaluation and studies for the advancement and acceleration of the ultrasonic imaging system, numerical simulations, prototyping and full-scale verification of the system, radiation resistance tests, construction of a submillimeter ultrasonic ranging system, application of the ultrasonic sub-millimeter ranging system to LIBS, as well as battery-powered remote operation of the measurement system. These outcomes are summarized in this report.
-iron at high pressures determined using 
neutron diffractionAoki, Katsutoshi*; Takano, Masahiro*; Fukuyama, Ko*; Kagi, Hiroyuki*; Machida, Akihiko*; Saito, Hiroyuki*; Hattori, Takanori; Sano, Asami; Funakoshi, Kenichi*
Physical Review B, 113(18), p.184440_1 - 184440_6, 2026/05
Times Cited Count：1The temperature dependence of the magnetic moment of bcc -iron was investigated over the range 300-950 K at pressures of approximately 2 and 6 GPa by neutron powder diffraction. The 
Fe isotope, whose neutron scattering length is approximately half that of naturally abundant Fe, was employed to enhance the relative contribution of magnetic scattering. Curie temperatures (
) were determined to be 946(30) K, 838(50) K and 740(40) K at 2.1, 6.0 and 6.7 GPa, respectively, defining a magnetic phase boundary described by (K) = 1043 - 49(7)
+ 1.3(1.2)
. Upon heating at 6.7 GPa, the 
structural transition was observed to follow the magnetic transition. This transition sequence indicates that the magnetic phase boundary lies on the low-temperature side of the phase boundary. Accordingly, the transition corresponds to a structural transformation from paramagnetic bcc to paramagnetic fcc iron.
Takahashi, Naoki*; Sakamaki, Tatsuya*; Hattori, Takanori; Funakoshi, Kenichi*; Arima-Osonoi, Hiroshi*; Sano, Asami; Abe, Jun*; Suzuki, Akio*
Scientific Reports (Internet), 16, p.14162_1 - 14162_13, 2026/05
Times Cited Count：0We performed high-pressure and high-temperature neutron diffraction and imaging experiments in situ to determine the hydrogen content in liquid iron. We observed that liquid iron contains 0.17(3) wt.% H at 3.4 GPa and 1400 K, indicating that liquid iron is hydrogenated in the magma ocean during core formation. For the hydrogen content in the liquid iron at the base of the magma ocean, we estimated that the outer and inner cores contain 0.60-0.72 and 0.30-0.44 wt.% H, corresponding to 70-85 and 1.9-2.7 times the mass of hydrogen in the ocean, respectively. This suggests that hydrogen can contribute more than half of the density deficit in the outer core. For the magma ocean equilibrating with the hydrogen-rich primary atmosphere, the study findings show that liquid iron plays a crucial role in transporting a large amount of hydrogen into the core.
Sakakibara, Ryotaro*; Terasawa, Tomoo; Kawauchi, Taizo*; Fukutani, Katsuyuki; Ito, Takahiro*; Norimatsu, Wataru*
Small Methods, 10(8), p.e01889_1 - e01889_12, 2026/04
Times Cited Count：0 Percentile：0.00(Chemistry, Physical)Department of Radiation Protection, Nuclear Science Research Institute; Nuclear Facilities Management Section, Aomori Research and Development Center
JAEA-Review 2025-055, 107 Pages, 2026/03
JAEA-Review-2025-055.pdf:2.26MB
This annual report describes the activities in the 2024 fiscal year of Department of Radiation Protection at Nuclear Science Research Institute, Harima Synchrotron Radiation Radioisotope Laboratory, and Nuclear Facilities Management Section at Aomori Research and Development Center. The activities described in this report are environmental monitoring, radiation protection practices in workplaces, individual monitoring, maintenance of monitoring instruments, and research and development of radiation protection. At these institutes, the occupational exposures did not exceed the dose limits. The radioactive gaseous and liquid discharges from the facilities were well below the prescribed limits. The research and development activities in the field of radiological protection were continued.
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
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)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.
Fukushima Research and Engineering Institute*
JAEA-Evaluation 2025-001, 23 Pages, 2025/09
JAEA-Evaluation-2025-001.pdf:0.72MB
JAEA-Evaluation-2025-001-appendix(CD-ROM).zip:185.38MB
Japan Atomic Energy Agency (hereinafter referred to as "JAEA") consulted an assessment committee, "Evaluation Committee of Research and Development related to the Accident at TEPCO's Fukushima Daiichi Nuclear Power Station" (hereinafter referred to as "Committee") for ex-ante evaluations of "Research and Development Related to the Accident at TEPCO's Fukushima Daiichi Nuclear Power Station" in accordance with "General Guideline for the Evaluation of Government Research and Development (R&D) Activities" by Cabinet Office, Government of Japan, "Guideline for Evaluation of R&D in Ministry of Education, Culture, Sports, Science and Technology" and "Regulation on Conduct for Evaluation of R&D Activities" by JAEA. Based on a request from JAEA, the committee conducted a post-evaluation of research and development activities in the fourth phase (April 2022 to March 2029) of the medium-term research plan. This report summarizes the results of the assessment by the Committee.
Wilson, J.*; Sasamoto, Hiroshi; Tachi, Yukio; Kawama, Daisuke*
Applied Clay Science, 275, p.107862_1 - 107862_15, 2025/05
Times Cited Count：6 Percentile：74.30(Chemistry, Physical)High-Level Radioactive Waste (HLW) repositories include iron or steel-based containers/overpack and bentonite buffers. Over the last 25 years or so, research efforts have attempted to elucidate the nature of iron-bentonite interactions, especially the potential for the deleterious alteration of the swelling clay component (smectite), to iron-rich layer silicates, some of which lack the capacity for intracrystalline swelling. This could result in a reduction or loss in swelling pressure in the bentonite buffer which is designed to protect waste containers from shear forces and also acts to restrict water and solute transport, as part of an engineered barrier system. Most data on iron-bentonite interactions come from experimental and geochemical modelling studies, as natural analogue data are lacking. The data suggests that there is the potential for the development of an iron-rich bentonite alteration zone with smectite (generally present as the aluminous montmorillonite type) undergoing alteration to iron-rich solids, including layer silicates and steel corrosion products such as green rust or magnetite. The evidence available is complex, arguably incomplete, with many potential complex couplings. Many uncertainties remain despite efforts taken over the last 25 years, but plausible scenarios for iron-bentonite interactions have been identified and possible implications for buffer properties have been suggested.
Usami, Hiroshi; Yoshinaga, Kyohei*; Fujikawa, Keigo*
Nihon Genshiryoku Gakkai-Shi ATOMO
, 67(5), p.295 - 299, 2025/05
no abstracts in English
Aoki, Katsutoshi*; Machida, Akihiko*; Saito, Hiroyuki*; Hattori, Takanori
Koatsuryoku No Kagaku To Gijutsu, 35(1), p.4 - 11, 2025/03
Iron reacts with hydrogen to form solid solutions with body-centered cubic, face-centered cubic, hexagonal close packed, and double hexagonal close packed structures at high temperatures and high pressures. Neutron diffraction is the most powerful tool for determining the occupation sites and occupancies of hydrogen atoms dissolved in a metal lattice. Structural parameters, including hydrogen occupation sites and occupancies, are refined via Rietveld analysis for neutron diffraction data. We present our expertise in Rietveld refinement of iron hydrides accumulated over 10 years.
Sayato, Natsuki; Otsuka, Kaoru; Fuyushima, Takumi; Endo, Yasuichi; Otsuka, Noriaki; Kitagishi, Shigeru; Tobita, Masahiro*; Isozaki, Futoshi*; Matsumoto, Satoshi*; Takemoto, Noriyuki
JAEA-Technology 2024-016, 247 Pages, 2025/02
JAEA-Technology-2024-016.pdf:28.43MB
Japan Materials Testing Reactor (JMTR, 50MW) was selected as a project to be subsidized by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) for the "Establishment of an International Research and Development Center through Advanced Utilization of the World's Most Advanced Research Reactor". As part of this project, JMTR has installed "LWR Water Environment Simulation Tests" since 2010. This facility can control temperature, pressure, and water quality (dissolved oxygen, dissolved hydrogen, etc.) to simulate the water environment of light water reactors (BWR and PWR) and perform neutron irradiation of in-core structural materials, etc. In addition, this facility is also designed for PWR conditions. Chemical injection system for adding boron and lithium was added to the facility for PWR conditions. After the equipment was installed, test operation was carried out to confirm the performance of the facility. This report summarizes the establishment and test operation of LWR Water Environment Simulation Tests after the establishment.
Okazaki, Nobuo*; Hattori, Takanori
CROSS Reports (Internet), 3, p.001_1 - 001_8, 2025/02
There have been requests for remote analysis of measured data at the BL11 PLANET beamline in the Materials and Life Science Experimental Facility (MLF) of the Japan Proton Accelerator Research Complex (J-PARC), but a system to perform this analysis on a regular basis has not been established. In order to meet this demand, a system for remote analysis was established using NoMachine, which is widely used as a remote desktop connection environment. This system is built on the cloud, and users can analyze data from anywhere with an Internet environment by using the NoMachine client.
Metcalfe, R.*; Benbow, S. J.*; Kawama, Daisuke*; Tachi, Yukio
Science of the Total Environment, 958, p.177690_1 - 177690_17, 2025/01
Uplifting fractured granitic rocks occur in substantial areas of countries such as Japan. A repository site would be selected in such an area only if it is possible to make a safety case, accounting for the changing conditions during uplift. The safety case must include robust arguments that chemical processes in the rocks around the repository will contribute sufficiently to minimise radiological doses to biosphere receptors. To provide confidence in the safety arguments, numerical models need to be sufficiently realistic, but also parameterised conservatively (pessimistically). However, model development is challenging because uplift involves many complex couplings between groundwater flow, chemical reactions between water and rock, and changing rock properties. The couplings would affect radionuclide mobilisation and retardation, by influencing diffusive radionuclide fluxes between groundwater flowing in fractures and effectively immobile porewater in the rock matrix and radionuclide partitioning between water and solid phases, via: (i) mineral precipitation/dissolution; (ii) mineral alteration; and (iii) sorption/desorption. It is difficult to represent all this complexity in numerical models while showing that they are parameterised conservatively. Here we present a modelling approach, illustrated by simulation cases for some exemplar radioelements, to identify realistically conservative process conceptualisations and model parameterisations.
demand and HTGR development potential in the industrial complex in JapanNoguchi, Hiroki; Ishii, Katsunori; Ono, Masato; Kasahara, Seiji; Sato, Hiroyuki; Sakaba, Nariaki
Proceedings of World Hydrogen Technology Convention 2025 (WHTC 2025) (Internet), p.50 - 52, 2025/00
Achieving carbon neutrality in Japan in 2050, hydrogen is expected to be used as an alternative to fossil fuels in the hard-to-abate sectors. In steelmaking, hydrogen-based reduction process has been developed as a substitute for the conventional blast furnace steelmaking process, which involves the reduction of iron ore by coke. In chemical industry, a novel olefin production process has been developed using hydrogen and CO, through methanol as an intermediate chemical. A large amount of hydrogen is required for these novel processes. Nuclear energy is well-suited to large-scale low-carbon hydrogen production. High temperature gas cooled reactor (HTGR) is a type of nuclear reactor featuring extraction of high temperature heat. The heat can be applicable to hydrogen production. This study predicts hydrogen demand in five industrial complexes in Japan in 2050 and estimates the potential for introducing HTGR to meet the demand. The introduction of HTGR could be a promising solution for decarbonizing industrial complexes due to their large-scale hydrogen supply capacity.
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
Times Cited Count：7 Percentile：55.01(Environmental Sciences)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.
Metcalfe, R.*; Tachi, Yukio; Sasao, Eiji; Kawama, Daisuke*
Science of the Total Environment, 957, p.177375_1 - 177375_17, 2024/12
A safety case for an underground radioactive waste repository must show that groundwater will not in future transport radionuclides from the repository to the near-surface environment (the biosphere) in harmful quantities. Safety cases are developed step-wise throughout a programme to site and develop a repository. At early stages, before a site is selected, safety cases are generic and based on simplified safety assessment models of the disposal system that have conservative parameter values. Later, when site-specific conditions are known, more realistic models are needed for the long-term geo-environmental evolution and their impacts on radionuclide migration/retention. Uplift is one such environmental change, which may be particularly important in countries near active tectonic plate boundaries, such as Japan. Here we review the state of knowledge about how the properties of fractured granitic rocks evolve during uplift, based on studies in Japan. Hence, we present conceptual models and a generic scenario for mass transport and retardation processes in uplifting granitic rocks as a basis for realistic numerical models to underpin safety assessment.
Li, L.*; Miyamoto, Goro*; Zhang, Y.*; Li, M.*; Morooka, Satoshi; Oikawa, Katsunari*; Tomota, Yo*; Furuhara, Tadashi*
Journal of Materials Science & Technology, 184, p.221 - 234, 2024/06
Times Cited Count：13 Percentile：66.73(Materials Science, Multidisciplinary)Ishikado, Motoyuki*; Takahashi, Ryuta*; Yamauchi, Yasuhiro*; Nakamura, Masatoshi*; Ishimaru, Sora*; Yamauchi, Sara*; Kawamura, Seiko; Kira, Hiroshi*; Sakaguchi, Yoshifumi*; Watanabe, Masao; et al.
JPS Conference Proceedings (Internet), 41, p.011010_1 - 011010_7, 2024/05
Terasaka, Yuta; Iimoto, Takeshi*; Saso, Michitaka*; Fujita, Reiko*
Nihon Genshiryoku Gakkai-Shi ATOMO, 66(4), p.203 - 207, 2024/04
no abstracts in English
Facilities Safety Management Section, Safety Administration Department
JAEA-Review 2023-035, 218 Pages, 2024/03
JAEA-Review-2023-035.pdf:8.47MB
In September 2022, Japan Atomic Energy Agency (JAEA) published the 2021 Environmental Report concerning the activities of FY 2021 under "Act on the Promotion of Business Activities with Environmental Consideration by Specified Corporations, etc., by Facilitating Access to Environmental Information, and Other Measures". This report has been edited to show detailed environmental performance data in FY 2021 as the base of the 2021 Environmental Report. This report would not only ensure traceability of the data in order to enhance the reliability of the environmental report, but also make useful measures for promoting activities of environmental considerations in JAEA.
