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Yomogida, Takumi; Scaria, J.*; Fablet, L.*; Tokunaga, Kohei; Dei, Shuntaro; Higashi, Kotaro*; Kawamura, Naomi*; Takahashi, Yoshio*; Marsac, R.*
Chemical Communications, 61(91), p.17926 - 17929, 2025/11
This paper presents insights into the influence of magnetite stoichiometry (0 
R = Fe(II)/Fe(III) 0.5) on the surface reduction of U(VI) to U(V) and U(IV), as a key parameter controlling U redox speciation in natural settings. Although R can readily change due to the oxidation of structural Fe(II) or proton/ligand-promoted dissolution, prior studies have not quantified U(V) when assessing these effects. We employed U L
-edge HERFD-XANES spectroscopy to investigate the electronic structure of U on magnetite with varying stoichiometries and observed a peak splitting of U(V) on magnetite. Our results demonstrate the high stability of U(V) species under a wide range of conditions, and after 10 days on magnetite by the combination of MCR-ALS analysis. A key finding is that structural Fe(II), whose abundance depends on pH and redox conditions, plays a critical role for in the stabilization of U(V) on magnetite.
Collaborative Laboratories for Advanced Decommissioning Science; Yokohama National University*
JAEA-Review 2025-025, 90 Pages, 2025/10
JAEA-Review-2025-025.pdf:5.59MB
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 "Development of passive wireless communication systems operatable under inferior-wireless environment with obstacles" conducted in FY2023. This study aims to develop a wireless communication system for obstacle-dense environments by designing base stations, sensor nodes (SN), positioning algorithms, and wireless area formation methods for electromagnetic wave-shielded regions. Key outcomes are as follows: For direction-finding with high-performance antennas, triangulation positioning accuracy was evaluated, and a sensor information demodulation system was built. SNs with frequency-scanning analog and frequency-fixed digital methods achieved communication distances of 6-8 meters and wireless charging of 1-2 V in 3-15 minutes at 6 meters. Diode characteristics remained unchanged after 1,000 Gy radiation. Positioning algorithms using multipath tomography were validated with a high-resolution measurement system in the lab. Simulations with reactor building CAD diagrams optimized node numbers and arrangements. Wireless coverage in electromagnetic wave-shielded regions was tested using a composite antenna (patch array and waveguide), achieving a range of approximately 1.5 meters.
Luu, V. N.; Taniguchi, Yoshinori; Udagawa, Yutaka; Katsuyama, Jinya
Nuclear Engineering and Design, 442, p.114222_1 - 114222_15, 2025/10
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)Kamiya, Tomohiro; Yoshida, Hiroyuki
Physics of Fluids, 37(10), p.103359_1 - 103359_23, 2025/10
In this study, we developed a conservative scheme based on a volume of fluid (VOF) and a ghost fluid method for liquid-gas two-phase compressible fluid simulations. We treated several one- and two-dimensional numerical problems to investigate the capability and applicability of the proposed method for compressible two-phase fluid simulations. The results agree well with the exact solutions or the numerical results of previous studies. Furthermore, the results also show that the proposed method can almost completely ensure the conservation property. Consequently, we concluded that the proposed method could simulate compressible two-phase flows and conserve mass, momentum, and total energy.
Ito, Kei*; Matsushita, Kentaro; Ezure, Toshiki; Tanaka, Masaaki; Odaira, Naoya*; Ito, Daisuke*; Saito, Yasushi*
Nihon Kikai Gakkai 2025-Nendo Nenji Taikai Koen Rombunshu (Internet), 5 Pages, 2025/09
The estimation of entrained gas flow rate by a bathtub vortex is important in terms of a possibility to causes the performance degradation when the entrained bubbles are mixed into fluid machineries, e.g. pumps. In this study, to confirm the applicability of a model based on circulating annular flow model proposed by the authors, entrained gas flow rate is evaluated using the liquid velocity distribution around free surface dent of vortex (gas core), obtained by CFD data. As a result, it was indicated that it would be possible to evaluate the gas entrainment flow rate by setting an appropriate evaluation region.
Arai, Yoichi; Goto, Yasuhiro; Watanabe, So; Agou, Tomohiro*; Arai, Tsuyoshi*; Katsuki, Kenta*; Fukumoto, Hiroki*; Hoshina, Hiroyuki*; Seko, Noriaki*
Progress in Nuclear Science and Technology (Internet), 8, p.329 - 332, 2025/09
Chauvin, N.*; Martin, P.*; Ogata, Takanari*; Calabrese, R.*; Janney, D.*; Hirooka, Shun; Kato, Masato; Staicu, D.*; McClellan, K.*; White, J.*; et al.
NEA/NSC/R(2024)1 (Internet), 289 Pages, 2025/07
no abstracts in English
Auh, Y. H.*; Neal, N. N.*; Arole, K.*; Regis, N. A.*; Nguyen, T.*; Ogawa, Shuichi*; Tsuda, Yasutaka; Yoshigoe, Akitaka; Radovic, M.*; Green, M. J.*; et al.
ACS Applied Materials & Interfaces, 17(21), p.31392 - 31402, 2025/05
Times Cited Count：0 Percentile：0.00(Nanoscience & Nanotechnology)Fablet, L.*; P
drot, M.*; Choueikani, F.*; Kieffer, I.*; Proux, O.*; Pierson-Wickmann, A.-C.*; Cagniart, V.*; Yomogida, Takumi; Marsac, R.*
Environmental Science; Nano, 12(5), p.2815 - 2827, 2025/05
Times Cited Count：2 Percentile：90.52(Chemistry, Multidisciplinary)Nickel is an omnipresent trace element in the environment. Due to its high affinity for iron oxide nanoparticles, its elimination from soils and water by these nanoparticles represents an interesting strategy, specially by magnetites, which is naturally present in the environment. However, the interactions between Ni and magnetite are poorly understood, because of the difficulty to control the stoichiometry (Fe(II)-to-Fe(III) ratio) of magnetite. The behavior of Ni in the presence of magnetite nanoparticles with different stoichiometries, in aqueous solution and inert atmosphere, are probed by adsorption experiments and X-ray Absorption Spectroscopy. This study helps predicting the interactions between Ni and magnetite in environmental conditions, which can be used for the development of efficient remediation strategies.
Ueki, Taro
Proceedings of International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering (M&C 2025) (Internet), 10 Pages, 2025/04
The criticality analysis of continuously mixed random media is essential to the safe retrieval of fuel debris. Image analysis of an oxide debris mockup reveals that the power spectrum cannot be fully explained by a single factor alone, but instead requires consideration of the complexity of multiple factors. This highlights the need for a randomized function capable of representing complex power spectra. To address this, we developed a new function called the Randomized Fourier Series (RFS), which introduces randomization in amplitude and phase. RFS allows the representation of power spectra with arbitrary shapes, facilitating realistic Monte Carlo (MC) simulations of random continuous material mixtures. For demonstration, taking the Lorentz power spectrum as an example, the spectrum flatness at low wavenumbers is analyzed to understand how the transition to white noise influences the fluctuation in neutron effective multiplication factor across independently generated random media replicas. Numerical results are presented for a mixture of 4 materials, along with the root mean-squared mass deviation over the constituent materials. The MC solver Solomon is employed with a partial volume pairing feature.
Tomioka, Dai; Kochiyama, Mami; Ozone, Kenji; Nakata, Hisakazu; Sakai, Akihiro
JAEA-Technology 2024-023, 38 Pages, 2025/03
JAEA-Technology-2024-023.pdf:1.54MB
Japan Atomic Energy Agency is an implementing organization of near-surface disposal for low-level radioactive wastes generated from research, industrial and medical facilities in Japan. Information on the radioactivity concentration of these radioactive wastes is dispensable for the design and conformity assessment of the waste disposal facilities for the licensing application of the disposal project and its safety review. Radioactive Wastes Disposal Center has been improving the radioactivity evaluation procedure for the dismantling waste generated from the research reactors based on the activation calculation. In order to investigate the applicability of the ORIGEN code (included in SCALE6.2.4), which enables more accurate activation calculations using multigroup neutron spectra, we performed activation calculations with the ORIGEN-code and the ORIGEN-S code (included in SCALE6.0), which has been widely used in the past, for the dismantled wastes from the Rikkyo University Research Reactor, where radioactivity analysis data for the structural materials around the reactor core were compiled. As a result, the calculation time difference between ORIGEN and ORIGEN-S was small and the evaluated radioactivity concentrations of the former were in the range of 0.8-1.0 times those of the latter, which was in good agreement with those of radiochemical analysis in the range of 0.5-3.0 times. The applicability of ORIGEN was confirmed. In addition, activation calculations assuming trace elements in structural materials of nuclear reactor were performed with ORIGEN and ORIGEN-S and the results were compared. The causes of the large differences among 170 nuclides that are important for dose assessment in near-surface disposal were assessed each nuclide.
Yomogida, Takumi; Takahashi, Yoshio*
Chikyu Kagaku, 59(1), p.1 - 10, 2025/03
X-ray absorption fine structure XAFS spectroscopy techniques, which are applicable to almost all elements, provide information on elemental valence and local structure with high elemental selectivity and high sensitivity. It has become an indispensable method in space geochemistry and environmental chemistry. This review presents examples of the application of fluorescence XAFS methods to elements that are difficult to detect by conventional methods, and examples where new chemical species information has been obtained by increasing the energy resolution of the X-ray fluorescence (XRF) detection system to obtain XAFS.
Matsushita, Kentaro; Ezure, Toshiki; Tanaka, Masaaki; Imai, Yasutomo*; Fujisaki, Tatsuya*; Sakai, Takaaki*
Nuclear Engineering and Design, 432, p.113785_1 - 113785_16, 2025/02
Times Cited Count：1 Percentile：35.03(Nuclear Science & Technology)Establishing an evaluation method for the gas entrainment (GE) of argon cover gas due to surface vortices is required in terms of safety design of sodium-cooled fast reactors. To modify the evaluation model in an in-house evaluation tool for GE, StreamViewer, a modified evaluation model on the pressure distribution along the vortex center line (PVL model) was proposed to identify the vortex center lines by connecting continuous vortex center points from the suction port to the surface and evaluate gas core length based on the balance between the hydrostatic pressure and the pressure decrease distribution along the vortex center line. PVL model was applied the three-dimensional numerical analysis results for the experiments where a plate induced unsteady traveling vortices in the open channel flow. Consequently, the GE evaluation using StreamViewer with PVL model could reproduce the relation between the inlet flow velocity and the gas core length in the unsteady vortex flow experiments.
Kogawa, Hiroyuki; Wakui, Takashi; Futakawa, Masatoshi
Fluids (Internet), 10(1), p.3_1 - 3_15, 2025/01
Microbubbles have been applied in various fields. In mercury targets of spallation neutron sources, where cavitation damage is a crucial issue for the life estimation, microbubbles are injected into the mercury to absorb the thermal expansion of the mercury caused by the pulsed proton beam injection and reduce the macroscopic pressure waves, and result in reducing the damage. Recently, when the proton beam power was increased and the amount of injected gas bubbles was increased, unique damage morphologies were observed on solid-liquid interface. Detailed observation and numerical analyses revealed that the microscopic pressure emitted from the gas bubbles contracting is sufficient to form pit damage; i.e. the directions of streak-like defects which are formed by connecting pit damage coincides with the direction of gas bubble trajectories, and the distances between pits was understandable taking the natural period of gas bubble vibration into account. This indicates that the gas microbubbles to reduce the macroscopic pressure waves have potential to be inceptions of the cavitation damage due to the microscopic pressure emitted from gas bubbles. To completely mitigate the damage, we have to consider the two effects of injecting gas bubbles; reducing macroscopic pressure waves and microscopic pressure due to bubble dynamics.
Yomogida, Takumi
Hoshako, 38(1), p.19 - 25, 2025/01
High-energy-resolution fluorescence detection-X-ray absorption near-edge structure (HERFD-XANES) spectroscopy has enabled us to discuss the electronic structure of actinide compounds in more detail than with conventional XANES spectroscopy. We are conducting research with the aim of contributing to the prediction of the migration behavior of trace actinide elements in the environment by performing actinide speciation in various environmental samples. In this paper, we introduce the content of the discussion of the electronic state of U from the perspective of basic science, which is important for advancing application of HERFD-XANES spectroscopy to environmental science.
Calabrese, R.*; Hirooka, Shun
Progress in Nuclear Energy, 178, p.105516_1 - 105516_11, 2025/01
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)Thermal creep is one of the key properties of mixed oxide (MOX) fuel for innovative fast reactors. Thermal creep of fuel affects markedly the interaction between the fuel and the cladding. A review of correlations available in the literature is presented. The effect of porosity, plutonium concentration, and stoichiometry are discussed also in the light of recent numerical results. Our analysis pointed out some inconsistencies concerning the modelling of the effect of porosity on diffusional creep and a re-evaluation of the effect of plutonium concentration. The discussion suggested that Evans's findings on the effect of stoichiometry should be better assessed as well as the level of increase in creep moving towards stoichiometry. Typical operating conditions of fast breeder reactors confirmed the need for an extension of porosity and temperature correlations' domains. Besides this, a new correlation based on a separate-effect approach has been proposed for fuel performance codes.
Ono, Hirokazu
Genshiryoku Bakkuendo Kenkyu (CD-ROM), 31(2), p.140 - 143, 2024/12
In the geological disposal of high-level radioactive waste, after emplacement of an EBS, the near-field environment is affected by processes such as heat release from the waste, groundwater infiltration into the EBS, swelling and deformation of the buffer material, and chemical reactions between groundwater and minerals. It is crucial to develop simulation codes to evaluate such coupled thermal-hydraulic-stress-chemical (THMC) processes for safety assessment of geological disposal. The full-scale vertical-emplacement EBS experiment (Horonobe EBS experiment) has been undertaken in the 350 m gallery of the Horonobe Underground Research Laboratory (URL) with the Horonobe geological environment. In the Horonobe EBS experiment, various sensors were installed in the buffer and backfill material to obtain the data required to evaluate coupled THMC processes in near-field. In Task C of the Horonobe International Project (HIP), the dismantling experiment of the Horonobe EBS experiment will be carried out and the data obtained from this experiment will be used to understand the coupled processes and to evaluate the simulation code.
Collaborative Laboratories for Advanced Decommissioning Science; Yokohama National University*
JAEA-Review 2024-024, 88 Pages, 2024/11
JAEA-Review-2024-024.pdf:4.5MB
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 FY2022. 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 "Development of passive wireless communication systems operatable under inferior-wireless environment with obstacles" conducted in FY2022. The present study aims to develop a wireless system, sensor positioning algorithms, and wireless area formation technology for electromagnetically shielded areas. We developed a base station antenna and a sensor node that use 2.45 GHz for downlink and 4.9 GHz, which is the second harmonic, for uplink. We also confirmed that the developed circuit and antenna operate in a strong radioactive environment.
Yee-Rendon, B.; Jameson, R. A.*; Okamura, Masahiro*; Li, C.*; Jiang, P.*; Maus, J. M.*
Proceedings of 32nd Linear Accelerator Conference (LINAC 2024) (Internet), p.492 - 495, 2024/10
LINACs is a simulation framework for designing optics and beam dynamics of charged particles in particle accelerators. LINACs is an open-source software that enables the user complete control over all design and simulation parameters of RFQs. This includes beam-driven design, fully 3D simulation using precise quadrupolar symmetry, and rigorous Poisson solution for external and space charge fields. The code can handle simultaneous particle beams with analytical input distributions and allows input beam scans. The software offers a relatively short running time and provides extensive analysis techniques. This work provides a historical overview of the code, presents results from RFQ models, and discusses future developments.
Pla
ais, A.*; Bouly, F.*; Froidefond, E.*; Lagniel, J.-M.*; Normand, G.*; Orduz, A. K.*; Yee-Rendon, B.; De Keukeleere, L.*; Van De Walle, J.*
Proceedings of 32nd Linear Accelerator Conference (LINAC 2024) (Internet), p.563 - 568, 2024/10
Reliability is an important feature for high power particle accelerators. This is particularly true for Accelerator-Driven Systems (ADS), for that every beam interruption can strongly affect the availability of the nuclear reactor. Many of these outages come from the loss of accelerating cavities or of their associated systems. Cavity failures can be compensated for by retuning other cavities of the linac. Finding the ideal compensation settings is however a difficult challenge that involves beam dynamics and multi-objective optimisation, and which raises very different issues according to the linac under study. For instance in the SPIRAL2 linac, a lot of cavities are mobilized for the compensation and the search space has a very high number of dimensions. Plus, it has quite low margins on the longitudinal acceptance. Linacs for ADS (such as the Japan Atomic Energy Agency ADS or MYRRHA) have a specific fault-tolerance design which facilitate the optimisation, but cavities have to be retuned in a few seconds. Hence we developed LightWin, a tool to automatically and systematically find compensation settings for every cavity failure of any given linac. In this study, we will present LightWin latest developments as well as the compensation strategies that we developed for SPIRAL2 and ADS linacs, both from a beam dynamics and a mathematical point of view.
