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Kawaguchi, Munemichi*; Ikeda, Asuka; Saito, Junichi
Annals of Nuclear Energy, 226, p.111880_1 - 111880_9, 2026/02
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)Kokubu, Yoko; Nishio, Kazuhisa*; Takeuchi, Ryuji; Ikeda, Koki
JAEA-Data/Code 2025-014, 109 Pages, 2026/01
JAEA-Data-Code-2025-014.pdf:9.59MB
JAEA-Data-Code-2025-014-appendix(CD-ROM).zip:170.15MB
The Tono Geoscience Center of Japan Atomic Energy Agency (JAEA) has been conducting the groundwater pressure and hydrochemical monitoring to confirm the restoration process of the surrounding geological environment associated with the backfilling of shafts and tunnels of Mizunami Underground Research Laboratory (MIU). This report summarizes the data of the groundwater pressure and hydrochemical monitoring from boreholes and so forth at and around the MIU conducted in FY2024.
Kokubu, Yoko; Takeuchi, Ryuji; Nishio, Kazuhisa*; Ikeda, Koki
JAEA-Data/Code 2025-013, 66 Pages, 2026/01
JAEA-Data-Code-2025-013.pdf:5.88MB
The Tono Geoscience Center of Japan Atomic Energy Agency (JAEA) has been conducting the environmental monitoring investigation to confirm the environmental impacts associated with the backfilling of shafts and tunnels at the Mizunami Underground Research Laboratory (MIU). This report summarizes the results of the environmental impact investigations conducted as part of the environmental monitoring investigation around the MIU Site in FY2024, which include groundwater level measurement in wells, river flow rate measurement, water analysis of Hazama river, noise and vibration surveys, and soil survey.
Kaneda, Miyu*; Enomoto, Takamasa*; Kobayashi, Hiroyuki*; Fukada, Yukimasa; Kano, Jun*; Aoyagi, Yumito*; Fujii, Tatsuo*; Ikeda, Naoshi*
Japanese Journal of Applied Physics, 65(2), p.028001_1 - 028001_4, 2026/01
Times Cited Count：0 Percentile：0.00(Physics, Applied)Low-reflectance black materials play an important role in optical and thermal devices. In this study, boron-doped carbon nanowalls (CNWs) with extremely low reflectance were successfully synthesized using an inexpensive and simple experimental arrangement. Analysis of the nanostructures and surface morphology of the CNWs revealed that boron doped CNWs had a higher wall density and lower graphitization than undoped CNWs. We discuss the mechanism of light absorption in terms of stray light effects originating from the nanostructures and the improved electrical conductivity owing to carrier doping. Boron doped CNWs are considered beneficial for the implementation of this ultra-black material.
Teshigawara, Makoto; Ikeda, Yujiro*; Muramatsu, Kazuo*; Sutani, Koichi*; Kimijima, Koichi*; Fukuzumi, Masafumi*; Noda, Yohei*; Koizumi, Satoshi*; Kawamura, Yuji*; Saruta, Koichi; et al.
Canadian Journal of Physics, 103(12), p.1225 - 1231, 2025/12
Times Cited Count：0 Percentile：0.00(Physics, Multidisciplinary)Science using neutrons in the nanometer (nm) wavelength region as probes is expanding into a wide range of fields, from basic research in materials and life science to industrial applications. Dramatic increase in the intensity of the beam source is required to drive such research. We have focused on coherent scattering caused by nano-sized particle aggregations to increase the intensity of neutron beams. Nanodiamond is being vigorously researched and developed with the aim of practical application. On the other hand, we have focused on graphene, which has higher van der Waals forces by an order of magnitude and stronger bonding, sp2, between carbons than nanodiamond. This is expected to lead to its processability into a lumped for and to adapt to higher radiation fields. By promoting chemical vapor deposition (CVD), we have established a technique to form nano-sized graphene (called graphene flower) with a shape similar to a sunflower flower. In this talk, we report on the neutron scattering properties that contribute to the coherent scattering of the newly developed graphene flower.
-ordered FePt thin films studied by angle-dependent X-ray magnetic circular dichroismShibata, Goro; Ikeda, Keisuke*; Takanashi, Koki; Fujimori, Atsushi*; 8 of others*
Applied Physics Letters, 127(14), p.142406_1 - 142406_6, 2025/10
Times Cited Count：0 Percentile：0.00(Physics, Applied)Chiu, I.-H.; Osawa, Takahito; Sumita, Takehiro*; Ikeda, Mizuha*; Ninomiya, Kazuhiko*; Takeda, Shinichiro*; Minami, Takahiro*; Takahashi, Tadayuki*; Watanabe, Shin*
Applied Radiation and Isotopes, 222, p.111845_1 - 111845_7, 2025/08
Times Cited Count：1 Percentile：64.08(Chemistry, Inorganic & Nuclear)
He neutron spin filter at J-PARCTakahashi, Shingo; Kiyanagi, Ryoji; Okudaira, Takuya*; Takada, Shusuke*; Kobayashi, Ryuju; Okuizumi, Mao; Ino, Takashi*; Asai, Kanta*; Tsuchikawa, Yusuke; Oikawa, Kenichi; et al.
Nuclear Instruments and Methods in Physics Research A, 1075, p.170410_1 - 170410_8, 2025/06
Times Cited Count：1 Percentile：0.00(Instruments & Instrumentation)Kokubu, Yoko; Takeuchi, Ryuji; Nishio, Kazuhisa*; Ikeda, Koki
JAEA-Review 2024-066, 67 Pages, 2025/03
JAEA-Review-2024-066.pdf:8.25MB
The Tono Geoscience Center of the Japan Atomic Energy Agency has undertaken backfilling and restoration activities at the Mizunami Underground Research Laboratory (MIU) site since fiscal year 2020. These activities are being conducted in accordance with "The MIU Project from FY2020 Onwards," outlining the procedures for backfilling, restoration, and environmental monitoring at the MIU site. The backfilling activity was completed in January 2022, and thereafter, the observation of the backfilled shafts was commenced. On November 6, 2023, the settlement of the backfilled surface was observed in the Main Shaft and the Ventilation Shaft. By December 5, 2023, the depth of the settlement reached 12.9 m in the Main Shaft and 27.7 m in the Ventilation Shaft. After an evaluation by the MIU safety confirmation committee, which assessed the settlement condition and recommended countermeasures, the affected areas were backfilled for safety reasons. This report summarizes the observed settlement of the backfilled surface, the subsequent rebackfilling efforts, and the condition of the surface settlement areas. The condition of the backfilled sections has been confirmed up to June 2024.
-FeOOH; The Spin-reorientation transition and hydrogen-bond symmetrizationIkeda, Osamu*; Yamamoto, Hajime*; Sano, Asami; Sakamaki, Tatsuya*; Kuribayashi, Takahiro*; Noda, Yukio*; Suzuki, Akio*
Journal of the American Chemical Society, 147(5), p.4005 - 4016, 2025/02
Times Cited Count：3 Percentile：74.77(Chemistry, Multidisciplinary)The compression behavior of iron oxyhydroxide -FeOOH is complex, with variations in its magnetic property and bonding character. In this study, in situ powder neutron diffraction experiments were conducted on -FeOOH and -FeOOD up to pressures exceeding 20 GPa to investigate a spin-reorientation transition, hydrogen-bond symmetrization, and their correlation. The magnetic transition was observed at 8 GPa in both -FeOOH and -FeOOD. The crystal symmetry and H-bonds of -FeOOH transitioned from P21nm with asymmetric H-bonds to Pnnm with disordered H-bonds at 17.90 GPa, while -FeOOD remained asymmetric. The pressure evolution of the interatomic angles and distances indicates that the coordinate geometry of Fe transitioned toward H-bond symmetrization and would have affected the magnetic anisotropy.
Satou, Akira; Hibiki, Takashi*; Ikeda, Ryo; Shibamoto, Yasuteru
Progress in Nuclear Energy, 180, p.105593_1 - 105593_11, 2025/02
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)During a loss-of-coolant accident in a pressurized water reactor (PWR), there is a risk that pressurized thermal shock (PTS) may occur on the internal wall of the reactor pressure vessel (RPV) due to the flow of emergency core cooling (ECC) water injected into the cold leg that flows into the downcomer. PTS is caused by the rapid cooling of the downcomer wall by the ECC water and is strongly influenced by the temperature of the ECC water, the collision position and velocity of the water jet on the wall, the velocity of the liquid film on the wall, the thickness of the liquid film, and the spread of the downward flow. Therefore, the flow of ECC water discharging from the cold leg to the downcomer may strongly impact PTS events. To help understand this flow phenomenon, we reviewed studies on free outflow from a circular pipe. Experimental findings on the classification of flow conditions, transition conditions between flow conditions, end depth ratio, free surface profile of flow in the circular pipe, and shape of the nappe flowing out from the pipe have been obtained in a form that is almost consistent with each other. In contrast, when considering the flow from the cold leg to the downcomer, it is necessary to deal with the flow field in a specific situation, such as the flow into a narrow gap rather than a free space, the existence of rounded corners at the outlet of the circular pipe, and the influence of steam flow flowing from the core to the cold leg. However, few previous studies consider these factors, so we summarized them as knowledge that needs to be accumulated in the future.
Fukada, Yukimasa; Aoyagi, Yumito*; Yokoyama, Misaki*; Horibe, Yoichi*; Kano, Jun*; Kaneda, Miyu*; Fujii, Tatsuo*; Yoshigoe, Akitaka; Kobata, Masaaki; Fukuda, Tatsuo; et al.
Journal of Electronic Materials, 54, p.686 - 692, 2025/01
Times Cited Count：2 Percentile：29.75(Engineering, Electrical & Electronic)no abstracts in English
Teshigawara, Makoto; Lee, Y.*; Tatsumoto, Hideki*; Hartl, M.*; Aso, Tomokazu; Iverson, E. B.*; Ariyoshi, Gen; Ikeda, Yujiro*; Hasegawa, Takumi*
Nuclear Instruments and Methods in Physics Research B, 557, p.165534_1 - 165534_10, 2024/12
Times Cited Count：1 Percentile：27.91(Instruments & Instrumentation)At Japanese Spallation Neutron Source in J-PARC, the para-hydrogen fraction was measured by using Raman spectroscopy in-situ for an integrated beam power of 9.4 MW
h at 1 MW operation, to evaluate the functionality of the ferric oxyhydroxide catalyst. This result showed that full functionality of the catalyst was retained up to the 1 MW operation. We attempted to study the effect of neutron scattering driven para to ortho-hydrogen back-conversion rate in the absence of the catalyst effect with a bypass line without catalyst. The measured increase of ortho-hydrogen fraction was 0.44% for an integrated beam power of 2.4 MWh at 500 kW operation, however, which was considered to be due to not only to neutron collisions in cold moderators but also to the high ortho-hydrogen fraction of initially static liquid hydrogen in the bypass line and passive exudation of quasi-static hydrogen in the catalyst vessel to the main loop.
Sumita, Takehiro*; Osawa, Takahito; Chiu, I.-H.; Ikeda, Atsushi
Analytica Chimica Acta, 1329, p.343256_1 - 343256_10, 2024/11
Times Cited Count：1 Percentile：11.80(Chemistry, Analytical)Kobayashi, Taishi*; Sato, Yutaro*; Tonna, Ryutaro*; Matsumura, Daiju; Sasaki, Takayuki*; Ikeda, Atsushi
Dalton Transactions (Internet), 53(46), p.18616 - 18628, 2024/10
Times Cited Count：2 Percentile：31.94(Chemistry, Inorganic & Nuclear)Kusaka, Hiroyuki*; Ikeda, Ryosaku*; Sato, Takuto; Iizuka, Satoru*; Boku, Taisuke*
Journal of Advances in Modeling Earth Systems (Internet), 16(10), p.e2024MS004367_1 - e2024MS004367_38, 2024/10
Times Cited Count：10 Percentile：85.04(Meteorology & Atmospheric Sciences)To bridge the gaps between meteorological large-eddy simulation (LES) models and computational fluid dynamics (CFD) models for microscale urban climate simulations, the present study has developed a meteorological LES model for urban areas. This model simulates urban climates across both mesoscale (city scale) and microscale (city-block scale). The paper offers an overview of this LES model, which distinguishes itself from standard numerical weather prediction models by resolving buildings and trees at the microscale simulations. It also differs from standard CFD models by accounting for atmospheric stratification and physical processes. Noteworthy features of this model include: (a) the calculation of long- and short-wave radiations in three dimensions, incorporating multiple reflections within urban canopy layers using the radiosity method, and accounting for building and tree shadows in the simulations; (b) the provision of various heat stress indices (Universal Thermal Climate Index, Wet Bulb Globe Temperature, MRT, THI); (c) the assessment of the efficacy of heat stress mitigation measures such as dry-mist spraying, roadside trees, cool pavements, and green/cool roofs strategies; (d) the capability to run on supercomputers, with the code parallelized in a three-dimensional manner, and the model can also run on a graphics processing unit cluster. Following the introduction of this model, the study confirms its basic performance through various numerical experiments, including simulations of thermals in the convective boundary layer, coherent structure of turbulence over urban canopy, and thermal environment and heat stress indices in urban districts. The model developed in this study is intended to serve as a community tool for addressing both fundamental and applied studies in urban climatology.
Teshigawara, Makoto; Ikeda, Yujiro*; Muramatsu, Kazuo*; Sutani, Koichi*; Fukuzumi, Masafumi*; Noda, Yohei*; Koizumi, Satoshi*; Saruta, Koichi; Otake, Yoshie*
Journal of Neutron Research, 26(2-3), p.69 - 74, 2024/09
Slow neutrons, such as cold neutrons, are important non-destructive probes not only for basic physics but also for the structural genomics advancements in the life sciences and the battery technology advancements needed for the transition to a hydrogen society. Neutron-based science is also known as high-neutron-intensity-dependent science. A new unique method focusing on nanosized particle aggregation has been proposed to increase neutron intensity in that energy region. The method is based on intensity enhancement by multiple coherent scatterings with nanosized particle aggregation. The aggregation of nanosized particles matches the wavelength of below cold neutrons, causing a similar effect to coherent scattering, so-called Bragg scattering, leading to neutron intensity enhancement by several orders of magnitude. Nanodiamonds and magnesium hydride have recently been studied numerically and experimentally. The major challenge with nanodiamonds in practical applications is the molding method. Another carbon structure, graphene is focused on to find a solution to this problem. It is hypothesized that nanosized graphene could aid coherent neutron scattering under particle size conditions similar to nanodiamonds. We report the potential of nanosized graphene as a reflector material below cold neutrons, together with experimental results.
Yamamoto, Hajime*; Ikeda, Osamu*; Honda, Takashi*; Kimura, Kenta*; Aoyama, Takuya*; Ogushi, Kenya*; Suzuki, Akio*; Ishii, Kenji*; Matsumura, Daiju; Tsuji, Takuya; et al.
Physical Review Materials (Internet), 8(9), p.094402_1 - 094402_6, 2024/09
Times Cited Count：4 Percentile：32.24(Materials Science, Multidisciplinary)Namie, Masanari; Saito, Junichi; Ikeda, Asuka; Oka, Ryotaro*; Kim, J.-H.*
Surfaces (Internet), 7(3), p.550 - 559, 2024/09
Aoyagi, Noboru; Motokawa, Ryuhei; Okumura, Masahiko; Ueda, Yuki; Saito, Takumi*; Nishitsuji, Shotaro*; Taguchi, Tomitsugu*; Yomogida, Takumi; Sazaki, Gen*; Ikeda, Atsushi
Communications Chemistry (Internet), 7, p.128_1 - 128_13, 2024/06
Times Cited Count：2 Percentile：23.38(Chemistry, Multidisciplinary)