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Aizawa, Naoto*; Watanabe, Tomoaki; Chiba, Go*; Tada, Kenichi; Fujita, Tatsuya*; Yamamoto, Akio*
Nuclear Engineering and Technology, 58(5), p.104176_1 - 104176_16, 2026/05
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)
:Ce using PHITS track-structure simulationsHirata, Yuho; Kai, Takeshi; Ogawa, Tatsuhiko; Matsuya, Yusuke; Sato, Tatsuhiko; Watanabe, Kenichi*; Kato, Takumi*; Kawaguchi, Noriaki*; Yanagida, Takayuki*
Radiation Measurements, 193, p.107651_1 - 107651_8, 2026/04
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)CaF:Ce has a high potential to be used as a dosimeter due to its high optically stimulated luminescence (OSL) intensity. However, when phosphors such as CaF:Ce are irradiated with swift ions, the OSL intensity per dose decreases due to quenching effects. Traditionally, quenching effects in phosphors have been evaluated based on energy deposition density, using linear energy transfer (LET) as a metric. However, the relationship between quenching effects and LET varies with ion type, complicating unified evaluations. The track structure in PHITS can precisely simulate the radiation interactions. In this study, we simulated the detector response of CaF:Ce irradiated with swift-ions and compared these results with experimental data. The comparison suggests that the quantum yield of OSL is a critical parameter influencing the quenching effect in CaF:Ce. These findings are expected to contribute to the development of improved phosphor detectors.
Fujita, Natsuko; Maeta, Yusuke; Miyake, Masayasu*; Matsubara, Akihiro*; Uno, Sadanori*; Omae, Akiomi*; Jinno, Satoshi; Minamitani, Fumina; Watanabe, Takahiro; Nishio, Tomohiro; et al.
Dai-37-Kai Tandemu Kasokuki Oyobi Sono Shuhen Gijutsu No Kenkyukai Hokokushu, p.22 - 25, 2026/03
no abstracts in English
Hagiwara, Hiroki; Takaku, Atsushi*; Sagawa, Hiroshi*; Kanno, Futoshi*; Ito, Azusa; Ando, Taichi*; Ichihara, Masatsugu*; Watanabe, Yusuke; Koarai, Kazuma; Kato, Jun; et al.
Proceedings of Waste Management Symposia 2026 (WM2026) (Internet), 7 Pages, 2026/03
Watanabe, Tomoaki; Aizawa, Naoto*; Chiba, Go*; Tada, Kenichi; Fujita, Tatsuya*; Yamamoto, Akio*
Journal of Nuclear Science and Technology, 63(2), p.166 - 186, 2026/02
Times Cited Count：1 Percentile：54.69(Nuclear Science & Technology)A fast burnup calculation method based on neutron spectrum reconstruction is proposed. The method employs a reduced-order model (ROM), constructed using proper orthogonal decomposition (POD) and regression models, to estimate neutron spectra experienced by fuel during burnup. The ROM is built from snapshot data generated through detailed burnup and neutron transport simulations under various conditions. During burnup calculations, the ROM is used to rapidly reconstruct neutron spectra at each burnup step. These reconstructed spectra are then used to compute one-group cross sections from multi-group effective cross sections derived using background cross sections. The proposed method significantly reduces computational time by avoiding repeated neutron transport simulations. Its performance is demonstrated using a PWR UO
fuel pin model. Results show that, with the 6th-order POD, the method predicts nuclide inventories with an average error within 
5% compared to reference Monte Carlo calculations. Error analysis indicates that prediction accuracy is primarily limited by the regression models, rather than by the POD truncation or the multi-group cross section calculations.
Watanabe, Tomoaki; Tada, Kenichi; Endo, Tomohiro*; Yamamoto, Akio*
Journal of Nuclear Science and Technology, 63(1), p.3 - 18, 2026/01
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)This study investigated the impact of nuclear data updates from JENDL-4.0 (J4) to JENDL-5 (J5) on the light-water reactor fuel burnup calculations. Burnup calculations were conducted with J4 and J5 for PWR pin-cell and BWR fuel assembly geometries. The calculation results revealed significant burnup-dependent differences in the neutron multiplication factor (k
). Across the burnup range of 0-50 GWd/t, k
values of J5 were consistently smaller than those of J4 and the difference gradually increased as burnup progressed. Direct sensitivity calculations, in which each nuclide data was replaced from J4 to J5, indicated that updates to the cross-sections of 
U, 
U, and 
Pu and the thermal scattering law data of H in HO notably impacted the k differences. For the BWR assembly geometry containing Gd fuels, large k differences were observed in the burnup range of 10-15 GWd/t. This difference was primarily attributed to updates in the U, 
Gd, and 
Gd cross-sections, and thermal scattering law data of H in HO. Furthermore, we investigated how the nuclear data updates affected the k differences by examining nuclide number densities, the energy-dependent sensitivities, and the neutron spectra.
Hagiwara, Hiroki; Watanabe, Yusuke; Konishi, Hiromi*; Funaki, Hironori; Fujiwara, Kenso; Iijima, Kazuki
Applied Geochemistry, 190, p.106490_1 - 106490_10, 2025/10
Times Cited Count：0 Percentile：0.00(Geochemistry & Geophysics)Ishikawa, Akihisa; Segawa, Mariko; Toh, Yosuke; Watanabe, Kenichi*; Masuda, Akihiko*; Matsumoto, Tetsuro*; Yamazaki, Atsushi*; Yoshihashi, Sachiko*; Uritani, Akira*; Harano, Hideki*
Journal of Radiation Research (Internet), 66(5), p.563 - 569, 2025/09
Times Cited Count：1 Percentile：49.60(Biology)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
Hasegawa, Kenta; Ambai, Hiromu; Takahatake, Yoko; Watanabe, So; Nakamura, Masahiro; Sano, Yuichi; Takeuchi, Masayuki
Progress in Nuclear Science and Technology (Internet), 8, p.248 - 251, 2025/09
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.
-butadiene) reinforced by carbon blackWatanabe, Yuki*; Kumagawa, Daiki*; Karitani, Shu*; Inoue, Tadashi*; Iwabuki, Hitoshi*; Nakanishi, Yohei*; Shibata, Motoki*; Motokawa, Ryuhei; Sugita, Tsuyoshi; Ueda, Yuki; et al.
Macromolecules, 58(16), p.8641 - 8648, 2025/08
Times Cited Count：0 Percentile：0.00(Polymer Science)Chiu, I.-H.; Osawa, Takahito; Ninomiya, Kazuhiko*; Takeda, Shinichiro*; Takahashi, Tadayuki*; Katsuragawa, Miho*; Watanabe, Shin*; Kubo, Kenya*; Saito, Tsutomu*; Mizumoto, Kazumi*; et al.
npj Heritage Science (Internet), 13, p.154_1 - 154_9, 2025/05
Times Cited Count：1 Percentile：82.33(Humanities, Multidisciplinary)Watanabe, Tomoaki; Aizawa, Naoto*; Chiba, Go*; Tada, Kenichi; Yamamoto, Akio*
Proceedings of International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering (M&C 2025) (Internet), p.288 - 297, 2025/04
Currently, a major burnup calculation method for the nuclide composition of nuclear fuel conducts neutron transport calculations at each burnup step to account for changes in the neutron spectrum. While this method is highly accurate, the large computational cost of neutron transport calculations can be problematic. Therefore, a fast burnup calculation method based on neutron spectrum reconstruction with the proper orthogonal decomposition (POD) and regression model is investigated. In this method, dimensionality reduction by POD is applied to many neutron fluxes obtained from detailed burnup calculations for various input parameter sets, and regression models are constructed to connect the dimensionality-reduced neutron fluxes and parameters. By substituting arbitrary input parameters to the regression models, the neutron flux is reconstructed and the burnup calculation is performed. This method performs burnup calculations that consider changes in the neutron spectrum based on input conditions without neutron transport calculations. The present method was applied to a PWR UO fuel pin cell model. The results show the nuclide inventory can be calculated with a prediction accuracy within a few percent. In addition, it is found that the calculation error is dominated by the regression models, which implies the further improvement of the regression models leads to improving the accuracy.
Fujita, Natsuko; Miyake, Masayasu; Matsubara, Akihiro*; Ishii, Masahiro*; Jinno, Satoshi; Watanabe, Takahiro; Nishio, Tomohiro*; Ogawa, Yumi; Omae, Akiomi*; Kimura, Kenji; et al.
Dai-36-Kai Tandemu Kasokuki Oyobi Sono Shuhen Gijutsu No Kenkyukai Hokokushu, p.90 - 92, 2025/03
The JAEA-AMS-TONO facility at the Tono Geoscience Center, JAEA has three accelerator mass spectrometers. We report the present status of the JAEA-AMS-TONO.
Arai, Yoichi; Watanabe, So; Nakahara, Masaumi; Funakoshi, Tomomasa; Hoshino, Takanori; Takahatake, Yoko; Sakamoto, Atsushi; Aihara, Haruka; Hasegawa, Kenta; Yoshida, Toshiki; et al.
Progress in Nuclear Science and Technology (Internet), 7, p.168 - 174, 2025/03
The Japan Atomic Energy Agency (JAEA) has been conducting a project named "Systematic Treatment of RAdioactive liquid waste for Decommissioning (STRAD)" project since 2018 for fundamental and practical studies for treating radioactive liquid wastes with complicated compositions. Fundamental studies have been conducted using genuine liquid wastes accumulated in a hot laboratory of the JAEA called the Chemical Processing Facility (CPF), and treatment procedures for all liquid wastes in CPF were successfully designed on the results obtained. As the next phase of the project, new fundamental and practical studies on primarily organic liquid wastes accumulated in different facilities of JAEA are in progress. This paper reviews the representative achievements of the STRAD project and introduces an overview of ongoing studies.
Watanabe, Kaho; Suzuki, Kenta
JAEA-Testing 2024-004, 41 Pages, 2025/02
JAEA-Testing-2024-004.pdf:3.4MB
There is an emergency response team against nuclear facilities' accidents of Japan Atomic Energy Agency (JAEA). The team is in Naraha Center for Remote Control Technology Development (NARREC). Trainings of maneuvering emergency response robots are performed at NARREC by the team for operators temporarily coming from all facilities which are possibility to have a huge nuclear emergency in JAEA. There are three kinds of robots to be used in the training: (1) Reconnaissance robots (for shooting a video and for measuring radiation level and temperature in nuclear accidents field), (2) Work robots (for obstacles removal in nuclear accidents field) and (3) Drones. As for the training, each operator person has been trained once or twice a year. Therefore, it is difficult for operators to retain their own sense of the maneuvering robots. Then, the team provided a simulator system which is consists of a palm-sized controller and a PC installed operation programs based on Choreonoid as dynamics simulation software, and we provided the system for operators in order to supplement a real robot operation training. This report shows the operation method of the provided simulator system regarding one reconnaissance robot and two work robots.
AcOguri, Kaori; Watanabe, So; Arai, Yoichi; Shirasaki, Kenji*; Nakase, Masahiko*
Research Activity of RDG Collaboration Research in 2023, Institute for Materials Research, Tohoku University (Internet), p.D14 - D17, 2025/02
Actinium-225 (Ac) is focused from the viewpoint of cancer therapy using alpha particles. Ac can be produced with gamma-ray via 
Ra(gamma,n)Ra-Ac reaction. Since a radium (Ra) source must be secured to promote this production pathway, we set out to develop a Ra recovery technology. Ra, owing to the radioactive decay of primordial U, U, and 
Th, is a radioactive element commonly found within soils, sediments, and natural waters. Therefore, we have focused on extracting Ra from those things to build an effective process to create the Ra target. In this study, we performed sorption studies with Barium (Ba), homologs element of Ra, which may coexist with Ra in soil. The study of recovery methods for adsorbed elements, such as elution, requires clarification of the adsorption reaction mechanism as well as investigation of adsorption behavior. In order to elucidate local structure around Ba(II) loaded in the metal (hydr)oxides and certain clay minerals, Extended X-ray Absorption Fine Structure (EXAFS) analysis was also carried out. The results of these tests confirmed that Ba and Ra exhibit similar adsorption behavior for clay materials, and that Ba and Ra have the potential to form endospheric complexes for Mn oxides.
Sugiyama, Hitoshi*; Kato, Kenichi*; Sekine, Naoko*; Sekine, Yurina; Watanabe, Tomoaki*; Fukazawa, Tomoko*
Chemical Physics Letters, 856, p.141655_1 - 141655_8, 2024/12
Times Cited Count：17 Percentile：95.62(Chemistry, Physical)To investigate the effects of polymer hydrophilicity on structures of water in hydrogels, differential scanning calorimetry and X-ray diffraction measurements were performed. The results show that the amount of intermediate water in polyacrylamide (PAA) hydrogel is about 12% smaller than that in poly-
-dimethylacrylamide (PDMAA) hydrogel. Furthermore, it was found that the bound water in PAA hydrogel primarily exists around the surface of the polymer bundles, whereas that in PDMAA hydrogel acts as a crosslinker factor for dehydration and water absorption in hydrogels.
Ishikawa, Akihisa; Tanaka, Hiroki*; Nakamura, Satoshi*; Kumada, Hiroaki*; Sakurai, Yoshinori*; Watanabe, Kenichi*; Yoshihashi, Sachiko*; Tanagami, Yuki*; Uritani, Akira*; Kiyanagi, Yoshiaki*
Journal of Radiation Research (Internet), 65(6), p.765 - 775, 2024/11
Times Cited Count：3 Percentile：36.42(Biology)