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Nakai, Noa; Urashima, Shuhei; Watanabe, Masayuki; Sekikawa, Takuya; Kusaka, Ryoji
Journal of Physical Chemistry Letters (Internet), 17(27), p.7734 - 7738, 2026/07
Times Cited Count：0 Percentile：0.00(Chemistry, Physical)
O solutionKumagai, Yuta; Kusaka, Ryoji; Takano, Masahide; Watanabe, Masayuki
Journal of Nuclear Materials, 625, p.156553_1 - 156553_7, 2026/04
Times Cited Count：0 Percentile：0.00(Materials Science, Multidisciplinary)Uranium-zirconium oxide solid solution, (U, Zr)O, is a representative matrix phase found in fuel debris formed during severe nuclear reactor accidents. Understanding its chemical behavior in oxidative aqueous environments is important for evaluating the potential release of radionuclides during water contact. In this study, we investigated the reactivity of (U, Zr)O with hydrogen peroxide (HO) in pure water to assess its resistance to oxidative dissolution, because HO is the dominant oxidant produced by water radiolysis. The dissolution behavior of uranium and zirconium was monitored through repeated HO exposure experiments, and the solid phases were characterized using Raman micro-spectroscopy and X-ray diffraction. Kinetic modeling was performed to interpret experimental data. The results showed that uranium dissolution occurred initially but decreased significantly upon repeated HO exposure, while zirconium dissolution proceeded more slowly. Raman analysis revealed only minor surface changes, with limited formation of uranyl peroxide phases. The kinetic simulation reproduced the experimental trends by assuming a small fraction of redox-active surface sites. These findings suggest that the observed durability of (U, Zr)O against HO-induced oxidative dissolution is not due to the formation of a protective surface layer, but rather reflects the limited redox reactivity of most of the surface. This study provides a quantitative basis for understanding the HO-induced oxidation of (U, Zr)O in water, relevant to the long-term behavior of fuel debris.
Chimura, Motoki; Watanabe, Kazuhiko*; Takahashi, Hiroki; Hirano, Koichiro; Shinto, Katsuhiro; Kitamura, Ryo; Kawase, Masato*; Suzuki, Takahiro*; Morishita, Takatoshi
Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.709 - 713, 2026/03
no abstracts in English
Iketani, Shotaro; Suzuki, Takeshi; Yokobori, Tomohiko; Sugawara, Satoshi; Yokota, Akira; Kikuchi, Genta; Muraguchi, Yoshinori; Kitahara, Masaru; Seya, Manato; Kurosawa, Tsuyoshi; et al.
JAEA-Technology 2025-001, 169 Pages, 2025/08
JAEA-Technology-2025-001.pdf:14.22MB
The radioactive waste treatment facilities at the Nuclear Science Research Institute includes the Radioactive Waste Treatment Facility No. 3, Waste Size Reduction and Storage Facility, and Waste Volume Reduction Facility. These three facilities come under the purview of the Act on the Regulation of Nuclear Source Material, Nuclear Fuel Material and Reactors, and are included under Class C of the act based on the seismic requirements specified in the Act. We assessed the seismic capacity of these three radioactive waste treatment facilities based on the current Building Standards Act, to verify whether they comply with the new regulatory requirements enforced by the Nuclear Regulation Authority (NRA) in the aftermath of the 2011 nuclear accident at the Fukushima Daiichi Nuclear Power Station operated by the Tokyo Electric Power Company. We found that the allowable stress of a few structural members used in the construction of the facilities did not meet the regulatory requirements. After studying the approval granted by the NRA for the construction plans, including the design and construction methods (design and construction plans) of the three facilities on March 5, 2021, we made aseismic reinforcement at these facilities between 2021 and 2022. This report presents an overview of the seismic design of these facilities and an outline of the aseismic reinforcement conducted, management system existing, safety measures adopted, and the preoperational inspections conducted at these facilities.
Tashiro, Shinsuke; Uchiyama, Gunzo; Ono, Takuya; Amano, Yuki; Yoshida, Ryoichiro; Watanabe, Koji*; Abe, Hitoshi; Yamane, Yuichi
Nuclear Technology, 211(3), p.429 - 438, 2025/03
Times Cited Count：1 Percentile：16.94(Nuclear Science & Technology)Contributing to the confinement safety evaluation of glove-box (GB) connected with high efficiency particle air (HEPA) filters for radioactive materials under fire accidents, combustion tests of a flammable polymer, Polymethyl methacrylate (PMMA), and a flame retardant polymer, Polycarbonate (PC), as typical GB panel resins have been conducted with an engineering-scale combustion apparatus. The combustion properties such as the mass loss rate (MLR) and the heat release rate (HRR) of PMMA and PC were investigated in the combustion tests. In the tests with the same shapes, it was found the followings; MLRs and HRRs of PMMA were larger than those of PC under the same supply flow rate into the combustion cell (Fv); MLRs and HRRs of PMMA and PC were constant under different Fv. Moreover, in the tests of PMMA with different cross section areas (S), MLRs and HRRs were found to be proportional to S. Using these results, the relationships of MLR and HRR to S of PMMA and PC were deduced.
Sb
with a honeycomb networkAdachi, Tadashi*; Ogawa, Taiki*; Komiyama, Yota*; Sumura, Takuya*; Saito-Tsuboi, Yuki*; Takeuchi, Takaaki*; Mano, Kohei*; Manabe, Kaoru*; Kawabata, Koki*; Imazu, Tsuyoshi*; et al.
Physical Review B, 111(10), p.L100508_1 - L100508_6, 2025/03
Times Cited Count：1 Percentile：21.19(Materials Science, Multidisciplinary)Arai, Tsuyoshi*; Nakamura, Fumiya*; Abe, Ryoji*; Ueno, Fuga*; Seko, Noriaki*; Arai, Yoichi; Watanabe, So
Progress in Nuclear Science and Technology (Internet), 7, p.147 - 153, 2025/03
no abstracts in English
Nakahara, Masaumi; Watanabe, So; Ishii, Yasuyuki*; Yamagata, Ryohei*; Yuri, Yosuke*; Yuyama, Takahiro*; Ishizaka, Tomohisa*; Koka, Masashi*; Yamada, Naoto*; Hagura, Naoto*
Nuclear Instruments and Methods in Physics Research B, 554, p.165449_1 - 165449_5, 2024/09
Times Cited Count：0 Percentile：0.00(Instruments & Instrumentation)Ion beam induced luminescence analysis of lanthanide complexes in the organic solvents for minor actinides recovery process was carried out to investigate the structures of complexes. In this study, hydrogen ion beam obtained from the single-ended accelerator and argon ion beam obtained from the azimuthally varying field cyclotron were used in Takasaki Ion Accelerators for Advanced Radiation Application in National Institutes for Quantum Science and Technology. In the experiments, ion beam induced luminescence spectra of lanthanide complexes in the organic solvents were measured, and the relationship between the obtained spectra and the structures of complexes was studied.
Nemoto, Takahiro; Fujiwara, Yusuke; Arakawa, Ryoki; Choyama, Yuya; Nagasumi, Satoru; Hasegawa, Toshinari; Yokoyama, Keisuke; Watanabe, Masashi; Onishi, Takashi; Kawamoto, Taiki; et al.
JAEA-Technology 2024-003, 17 Pages, 2024/06
JAEA-Technology-2024-003.pdf:1.91MB
In order to investigate the cause of the increase in differential pressure in the primary helium circulator filter that occurred during the RS-14 cycle, a clogged filter was investigated. As a result of the investigation, deposits caused by silicone oil were confirmed on the surface of the filter element. These results revealed that the cause of filter clogging was silicone oil mixed into the primary system due to performance deterioration of the charcoal filter in the gas circulator of primary helium purification system. As a measure to prevent the recurrence of this event, in addition to the conventional management based on operating hours for replacing of charcoal filter in the gas circulator of primary helium purification system, we have established a new replacement plan for every three years.
Ichikawa, Tsubasa*; Hakoshima, Hideaki*; Inui, Koji*; Ito, Kosuke*; Matsuda, Ryo*; Mitarai, Kosuke*; Miyamoto, Koichi*; Mizukami, Wataru*; Mizuta, Kaoru*; Mori, Toshio*; et al.
Nature Reviews Physics (Internet), 6(6), p.345 - 347, 2024/06
Times Cited Count：19 Percentile：98.39(Physics, Applied)Ito, Kotaro*; Tamura, Kazuhisa; Shimizu, Keisuke*; Yamada, Norifumi*; Watanabe, Kenta*; Suzuki, Kota*; Kanno, Ryoji*; Hirayama, Masaaki*
RSC Applied Interfaces (Internet), 1(4), p.790 - 799, 2024/04
LiCoO
is widely used as a cathode material in lithium-ion batteries. However, the reversible capacity of LiCoO at high voltage is not well known because of the oxidative degradation of the electrolyte. In this study, a thin-film all-solid-state battery was fabricated with epitaxially grown LiCoO cathode and Li
PO
solid electrolyte as a model battery that operates stably at high voltages, ranging up to 4.6 V, without drastic degradation. However, the charge-discharge capacities of the battery decreased with cycling at 4.7 V. 
synchrotron X-ray diffraction studies revealed that LiCoO was deactivated via a change in its crystal structure to O1 type, with narrow interlayer distances, at 4.7 V. The reduced distance between the interlayers in the O1 structure possibly prevents the re-intercalation of Li ions, leading to irreversibility.
Sano, Naruto; Yamashita, Naoki; Watanabe, Masaya; Tsukada, Manabu*; Hoshino, Kazutoyo*; Hirai, Koki; Ikegami, Yuta*; Tashiro, Shinsuke; Yoshida, Ryoichiro; Hatakeyama, Yuichi; et al.
JAEA-Technology 2023-029, 36 Pages, 2024/03
JAEA-Technology-2023-029.pdf:2.47MB
At the Waste Safety Testing Facility (WASTEF), the gamma ray irradiation device "Gamma Cell 220" was relocated from the 4th Research Building of the Nuclear Science Research Institute in FY2019, and the use of gamma ray irradiation has begun. Initially, Fuel Cycle Safety Research Group, Fuel Cycle Safety Research Division, Nuclear Safety Research Center, Sector of Nuclear Safety Research and Emergency Preparedness, the owner of this device, conducted the tests as the main user, but since 2022, other users, including those outside the organization, have started using it. The gamma ray irradiation device "Gamma Cell 220" is manufactured by Nordion International Inc. in Canada. Since it was purchased in 1989, the built-in 
Co radiation source has been updated once, and safety research related to nuclear fuel cycles, etc. It is still used for this purpose to this day. This report summarizes the equipment overview of the gamma ray irradiation device "Gamma Cell 220", its permits and licenses at WASTEF, usage status, maintenance and inspection, and future prospects.
He spin filter and small-angle X-ray scatteringRyoki, Akiyuki*; Watanabe, Fumi*; Okudaira, Takuya*; Takahashi, Shingo*; Oku, Takayuki; Hiroi, Kosuke; Motokawa, Ryuhei; Nakamura, Yo*
Journal of Chemical Physics, 160(11), p.114907_1 - 114907_9, 2024/03
Times Cited Count：2 Percentile：20.65(Chemistry, Physical)Nakahara, Masaumi; Watanabe, So; Yuyama, Takahiro*; Ishizaka, Tomohisa*; Yuri, Yosuke*; Ishii, Yasuyuki*; Yamagata, Ryohei*; Yamada, Naoto*; Koka, Masashi*; Kada, Wataru*; et al.
QST-M-47; QST Takasaki Annual Report 2022, P. 64, 2024/03
An extraction chromatography method has been studied to recover minor actinides from high-level liquid waste. For effective elution of minor actinides in an adsorbent, the structures of complexes are attempted to be evaluated with ion beam induced luminescence. In this study, Eu complexes in the adsorbent were irradiated by Ar
ion beam, and the ion beam induced luminescence spectra of Eu complexes were measured to evaluate the structures of Eu complexes.
Yoshimoto, Masataka*; Tamura, Kazuhisa; Watanabe, Kenta*; Shimizu, Keisuke*; Horisawa, Yuhei*; Kobayashi, Takeshi*; Tsurita, Hanae*; Suzuki, Kota*; Kanno, Ryoji*; Hirayama, Masaaki*
Sustainable Energy & Fuels (Internet), 8(6), p.1236 - 1244, 2024/03
Times Cited Count：2 Percentile：13.39(Chemistry, Physical)Photo-rechargeable systems, which can efficiently convert and store solar energy into chemical energy within single devices, are essential to harness sunlight effectively. Photo-(de)intercalation plays a pivotal role in the functionality of photorechargeable systems. Nevertheless, the photo-(de)intercalation process has not been conclusively confirmed owing to potential interference from side reactions, such as the decomposition of liquid electrolytes and the elution of electrode materials. In this study, we successfully demonstrated photo-responsive Li
-deintercalation using an all-solid-state thin-film battery comprised of epitaxially-grown anatase TiO doped with Nb (a-TiO:Nb) as the cathode. Under light irradiation, Li-deintercalation occurred and was subsequently reversibly intercalated into a-TiO:Nb during discharge.
Watanabe, Kenta*; Horisawa, Yuhei*; Yoshimoto, Masataka*; Tamura, Kazuhisa; Suzuki, Kota*; Kanno, Ryoji*; Hirayama, Masaaki*
Nano Letters, 24(6), p.1916 - 1922, 2024/02
Times Cited Count：7 Percentile：52.19(Chemistry, Multidisciplinary)Electrochemistry has extended from reactions at solid/liquid interfaces to those at solid/solid interfaces. In this study, we achieve the stable photoelectrochemical reaction at the semiconductor-electrode/solid-electrolyte interface in Nb-doped anatase-TiO (a-TiO:Nb)/LiPO (LPO)/Li all-solid-state cell. The oxidative currents of a-TiO:Nb/LPO/Li increase upon light irradiation when a-TiO:Nb is located at a potential that is more positive than its flat-band potential. The photoelectrochemical reaction at the semiconductor/solid-electrolyte interface is driven by the same principle as that at semiconductor/liquid-electrolyte interfaces. Thus, we extend photoelectrochemistry to all-solid-state systems composed of solid/solid interfaces.
Yamada, Ryohei*; Tamakuma, Yuki*; Kuwata, Haruka*; Saigusa, Yumi*; Watanabe, Yuki; Hirota, Seiko*; Jin, Q.*; Cai, Y.*
Hoken Butsuri (Internet), 58(3), p.169 - 177, 2023/11
no abstracts in English
Nakahara, Masaumi; Watanabe, So; Takeuchi, Masayuki; Yuyama, Takahiro*; Ishizaka, Tomohisa*; Ishii, Yasuyuki*; Yamagata, Ryohei*; Yamada, Naoto*; Koka, Masashi*; Kada, Wataru*; et al.
Nuclear Instruments and Methods in Physics Research B, 542, p.144 - 150, 2023/09
Times Cited Count：6 Percentile：63.53(Instruments & Instrumentation)The structures of Eu complexes in the adsorbents prepared with various extractants were evaluated by ion beam induced luminescence analysis in an extraction chromatography for minor actinides recovery. The luminescence of Eu was measured with a proton beam obtained from the single-ended accelerator and an argon ion beam obtained from the azimuthally varying field cyclotron in Takasaki Ion Accelerators for Advanced Radiation Application in National Institutes for Quantum Science and Technology. In this study, it was confirmed that the spectral shape of Eu complexes in the adsorbents varied depending on the kinds of extractants, and the correlation between the change in the spectra and the structures of Eu complexes was investigated.
Nemoto, Takahiro; Arakawa, Ryoki; Kawakami, Satoru; Nagasumi, Satoru; Yokoyama, Keisuke; Watanabe, Masashi; Onishi, Takashi; Kawamoto, Taiki; Furusawa, Takayuki; Inoi, Hiroyuki; et al.
JAEA-Technology 2023-005, 33 Pages, 2023/05
JAEA-Technology-2023-005.pdf:5.25MB
During shut down of the HTTR (High Temperature engineering Test Reactor) RS-14 cycle, an increasing trend of filter differential pressure for the helium gas circulator was observed. In order to investigate this phenomenon, the blower of the primary helium purification system was disassembled and inspected. As a result, it is clear that the silicon oil mist entered into the primary coolant due to the deterioration of the charcoal filter performance. The replacement and further investigation of the filter are planning to prevent the reoccurrence of the same phenomenon in the future.
Kusaka, Ryoji; Kumagai, Yuta; Watanabe, Masayuki; Sasaki, Takayuki*; Akiyama, Daisuke*; Sato, Nobuaki*; Kirishima, Akira*
Journal of Nuclear Science and Technology, 60(5), p.603 - 613, 2023/05
Times Cited Count：10 Percentile：71.75(Nuclear Science & Technology)