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Tamura, Fumihiko; Okita, Hidefumi; Hotchi, Hideaki*; Saha, P. K.; Sato, Yoichi*; Yoshii, Masahito*; Omori, Chihiro*; Yamamoto, Masanobu; Seiya, Kiyomi*; Sugiyama, Yasuyuki*; et al.
JPS Conference Proceedings (Internet), 45, p.011129_1 - 011129_7, 2026/06
The current goal of the J-PARC Main Ring (MR) is an output beam power of 1.3 MW, with a beam intensity is 3.3e14 protons per pulse (ppp) at a repetition period is 1.16 s. The Rapid Cycling Synchrotron (RCS) delivers two bunches to the MR in each injection and eight bunches are accumulated in the MR with four injections. The harmonic number of the RCS is 2 and the maximum nunch intensity of the RCS is 4.2e13 protons per bunch (ppb). If the harmonic number of the RCS is set to 1 and the RCS can accelerate a single bunch with the same intensity of 8.3e13 ppp/ppb, the bunch intensity in the MR can be doubled to 8.3e13 ppb, which corresponds to the accumulated beam intensity of 6.6e14 ppp with eight bunches. In this presentation, the feasibility of single bunch acceleration in the RCS is discussed based on the longitudinal beam simulations.
Okita, Hidefumi; Moriya, Katsuhiro; Yamada, Ippei; Chimura, Motoki; Saha, P. K.; Harada, Hiroyuki; Shobuda, Yoshihiro; Yoshimoto, Masahiro; Tamura, Fumihiko; Yamamoto, Masanobu; et al.
JPS Conference Proceedings (Internet), 45, p.011130_1 - 011130_8, 2026/06
no abstracts in English
Tamura, Fumihiko; Okita, Hidefumi; Yamamoto, Masanobu; Yoshii, Masahito*; Omori, Chihiro*; Seiya, Kiyomi*; Sugiyama, Yasuyuki*; Nomura, Masahiro; Shimada, Taihei; Hasegawa, Katsushi*; et al.
Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.269 - 273, 2026/03
The replacement project for the Magnetic Alloy (MA) cavities of the 3GeV RCS at J-PARC has been underway for several years. The original cavities are the push-pull (PP) configuration, where rf current is supplied alternately from a pair of tetrode tubes to the electrodes on the upstream and downstream sides of the acceleration gap. All cavities are to be replaced with newly developed single-ended (SE) cavities. In PP cavities, significant unbalance in the operation of the upstream and downstream tetrodes due to multiharmonic rf occurs. This unbalance has been one of the limiting factor of beam intensity. This unbalance does not occur essentially in SE cavities. Currently, six of the twelve cavities have been replaced. The SE cavity does not have a configuration to cancel even-order higher harmonics, therefore the harmonic components are different from those of the original PP cavity. We report on the operational experience with the single-ended cavity at the J-PARC RCS.
Cl
Aoki, So; Abe, Yosuke; Abe, Hiroshi*; Watanabe, Yutaka*; Yamamoto, Masahiro*
Corrosion Science, 255, p.113119_1 - 113119_10, 2025/10
Times Cited Count：3 Percentile：56.20(Materials Science, Multidisciplinary)This study aimed to visualise the distribution of chloride in the corroded crevice of stainless steel and to evaluate the chloride content quantitatively. Crevice corrosion tests were carried out using Cl, a radioactive isotope of chloride, as a tracer in NaCl test solutions. After crevice corrosion tests, stainless steel specimens were placed on an imaging plate. The imaging plate was sensitised by 
-ray emitted by Cl adhering to the crevice. As a result, the chloride distribution in the corroded area inside the crevice was visualised. A calibration curve for the amount of Cl was obtained from the relationship between the time of photosensitivity to -ray emitted by Cl and the luminance of the imaging plate. The chloride content in the corroded crevice was quantitatively evaluated based on the calibration curve. These visualisation and quantitative evaluation methods were also applied to tests in which specimens were left in pure water after crevice corrosion tests, and the behaviour of chloride in crevice corrosion was discussed.
Soma, Yasutaka; Komatsu, Atsushi; Kaji, Yoshiyuki; Yamamoto, Masahiro*; Igarashi, Takahiro
Corrosion Science, 251, p.112897_1 - 112897_15, 2025/07
Times Cited Count：3 Percentile：56.20(Materials Science, Multidisciplinary)Experimental and modeling studies of the oxygen ingression at the crevices of stainless steels were conducted in high-temperature water (288
C). The limiting distance of oxygen ingression, 
, was defined as the point beyond which the primary surface oxide changed (hematite 
magnetite), regardless of crevice gap, oxygen concentration, and time. In situ measurements revealed increased electrical conductivity around the position indicating ion enrichment due to a differential oxygen concentration cell. increased with increasing crevice gap, oxygen concentration, and immersion time. Modeling study suggested that oxide layer growth reduced anodic dissolution and slowed oxygen consumption, allowing oxygen ingression with time.
Saha, P. K.; Harada, Hiroyuki; Tamura, Fumihiko; Okabe, Kota; Yoshimoto, Masahiro; Shobuda, Yoshihiro; Okita, Hidefumi; Kojima, Kunihiro; Nakanoya, Takamitsu; Hatakeyama, Shuichiro; et al.
Physical Review Accelerators and Beams (Internet), 28(7), p.074201_1 - 074201_23, 2025/07
Times Cited Count：1 Percentile：43.93(Physics, Nuclear)Kokubun, Yuji; Hosomi, Kenji; Seya, Natsumi; Nagaoka, Mika; Inoue, Kazumi; Koike, Yuko; Hasegawa, Ryo; Kubota, Tomohiro; Hirao, Moe; Iizawa, Shogo; et al.
JAEA-Review 2024-053, 116 Pages, 2025/03
JAEA-Review-2024-053.pdf:3.26MB
Based on the regulations (the safety regulation of Tokai Reprocessing Plant, the safety regulation of nuclear fuel material usage facilities, the radiation safety rule, the regulation about prevention from radiation hazards due to radioisotopes, which are related with the nuclear regulatory acts, the local agreement concerning with safety and environment conservation around nuclear facilities, the water pollution prevention act, and by law of Ibaraki Prefecture), the effluent control of liquid waste discharged from the Nuclear Fuel Cycle Engineering Laboratories of Japan Atomic Energy Agency has been performed. This report describes the effluent control results of the liquid waste in the fiscal year 2023. In this period, the concentrations and the quantities of the radioactivity in liquid waste discharged from the reprocessing plant, the plutonium fuel fabrication facilities, and the other nuclear fuel material usage facilities were much lower than the limits authorized by the above regulations.
Okita, Hidefumi; Tamura, Fumihiko; Yamamoto, Masanobu; Miyakoshi, Ryosuke*; Nomura, Masahiro; Shimada, Taihei; Yoshii, Masahito*; Omori, Chihiro*; Seiya, Kiyomi*; Hara, Keigo*; et al.
Proceedings of 21st Annual Meeting of Particle Accelerator Society of Japan (Internet), p.765 - 769, 2024/10
no abstracts in English
Tamura, Fumihiko; Sugiyama, Yasuyuki*; Okita, Hidefumi; Yamamoto, Masanobu; Yoshii, Masahito*; Omori, Chihiro*; Seiya, Kiyomi*; Nomura, Masahiro; Shimada, Taihei; Hasegawa, Katsushi*; et al.
Proceedings of 21st Annual Meeting of Particle Accelerator Society of Japan (Internet), p.774 - 776, 2024/10
The 3GeV RCS of J-PARC accelerates proton beams with a maximum beam intensity of 8e13 ppp, utilizing the features of magnetic alloy (MA) cavities. The beam is extracted in a single turn by kicker magnets, and immediately after the beam is extracted, a short voltage jump occurs in the cavity. This is due to a delay in the voltage control feedback, which takes a certain amount of time to respond to the step-like decrease of beam current upon single-turn extraction. In a wideband (Q=2) MA cavity, this response delay is observed as a voltage jump. This voltage jump can cause damage to the cavity system if the voltage at the time of extraction is high. Therefore, we prepared a logic to suppress the output synchronously with the beam extraction as a function of the LLRF control system. The details of the function and test results are reported.
Sato, Nobuaki*; Kameo, Yutaka; Sato, Soichi; Kumagai, Yuta; Sato, Tomonori; Yamamoto, Masahiro*; Watanabe, Yutaka*; Nagai, Takayuki; Niibori, Yuichi*; Watanabe, Masayuki; et al.
Introduction to Dismantling and Decommissioning Chemistry, 251 Pages, 2024/09
This book focuses on the dismantling and decommissioning of nuclear facilities and reactors that have suffered severe accidents. In Part 1, we introduce basic aspects ranging from fuel chemistry, analytical chemistry, radiation chemistry, corrosion, and decontamination chemistry to waste treatment and disposal. Then, Part 2 covers the chemistry involved in the decommissioning of various nuclear facilities, and discusses what chemical approaches are necessary and possible for the decommissioning of TEPCO's Fukushima Daiichi Nuclear Power Plants, how decommissioning should be carried out, and what kind of research and development and also human resource development are required for this.
Saha, P. K.; Harada, Hiroyuki; Shobuda, Yoshihiro; Chimura, Motoki; Okabe, Kota; Nakanoya, Takamitsu; Moriya, Katsuhiro; Yamamoto, Kazami; Tamura, Fumihiko; Okita, Hidefumi; et al.
Proceedings of 15th International Particle Accelerator Conference (IPAC'24) (Internet), p.939 - 942, 2024/07
Katano, Ryota; Oizumi, Akito; Fukushima, Masahiro; Pyeon, C. H.*; Yamamoto, Akio*; Endo, Tomohiro*
Nuclear Science and Engineering, 198(6), p.1215 - 1234, 2024/06
Times Cited Count：1 Percentile：11.68(Nuclear Science & Technology)In this study, we have demonstrated that data assimilation using lead and bismuth sample reactivities measured in the Kyoto University Critical Assembly A-core can successfully reduce the uncertainty of the coolant void reactivity in accelerator-driven systems derived from inelastic-scattering cross-sections of lead and bismuth. We re-evaluated and highlighted the experimental uncertainties and correlations of the sample reactivities for the data assimilation formula. We used the MCNP6.2 code to evaluate the sample reactivities and their uncertainties, and performed data assimilation using the reactor analysis code system MARBLE. The high-sensitivity coefficients of the sample reactivities to lead and bismuth allowed us to reduce the cross-section-induced uncertainty of the void reactivity of the accelerator-driven system from 6.3% to 4.8%, achieving a provisional target accuracy of 5% in this study. Furthermore, we demonstrated that the uncertainties arising from other dominant factors, such as minor actinides and steel, can be effectively reduced by using integral experimental data sets for the unified cross-section dataset ADJ2017.
Yamamoto, Yuri*; Minowa, Kazuki*; Takahatake, Yoko; Watanabe, So; Nakamura, Masahiro; Matsuura, Haruaki*
Electrochemistry (Internet), 92(4), p.043019_1 - 043019_4, 2024/04
Times Cited Count：0 Percentile：0.00(Electrochemistry)In the pyro-reprocessing of spent nuclear fuel, salt bath is normally used in several times, but at final moment, spent salt containing small amount of chloride nuclear fuel material is generated. In terms of managing nuclear fuel materials, it is desirable that the nuclear fuel materials should be recovered from the spent salt. We are proposing methods for recovering nuclear fuel materials using precipitation by oxide addition and distillation for reducing pressure techniques. In this study, we have focused on the behavior of manganese(II), which is one of the radioactivated products. As a result of experiments and thermodynamic simulation, it was found that manganese(II) is likely to be entrained in nuclear fuel materials. Therefore, it is necessary to add a step to separate manganese(II) from nuclear fuel materials.
Kokubun, Yuji; Nakada, Akira; Seya, Natsumi; Nagaoka, Mika; Koike, Yuko; Kubota, Tomohiro; Hirao, Moe; Yoshii, Hideki*; Otani, Kazunori*; Hiyama, Yoshinori*; et al.
JAEA-Review 2023-052, 118 Pages, 2024/03
JAEA-Review-2023-052.pdf:3.67MB
Based on the regulations (the safety regulation of Tokai Reprocessing Plant, the safety regulation of nuclear fuel material usage facilities, the radiation safety rule, the regulation about prevention from radiation hazards due to radioisotopes, which are related with the nuclear regulatory acts, the local agreement concerning with safety and environment conservation around nuclear facilities, the water pollution control law, and by law of Ibaraki Prefecture), the effluent control of liquid waste discharged from the Nuclear Fuel Cycle Engineering Laboratories of Japan Atomic Energy Agency has been performed. This report describes the effluent control results of the liquid waste in the fiscal year 2022. In this period, the concentrations and the quantities of the radioactivity in liquid waste discharged from the reprocessing plant, the plutonium fuel fabrication facilities, and the other nuclear fuel material usage facilities were much lower than the limits authorized by the above regulations.
Yamamoto, Masahiro*; Igarashi, Takahiro
Corrosion Modelling with Cellular Automata; European Federation of Corrosion Publications, Number 71, p.131 - 153, 2024/03
In order to elucidate corrosion phenomena in spent fuel reprocessing plant, experimental corrosion tests and computer simulations were carried out. From experimental results, variation of intergranular corrosion rate were caused by following; (i) surface corrosion, (ii) increase of corrosion rate due to a part of grains dropping out, (iii) high corrosion rate due to continuous of dropping out of grains. Intergranular corrosion rates obtained from the simulation using the developed intergranular corrosion model were relatively good agreement with those from the experimental data.
Yamamoto, Tomohiko; Kato, Atsushi; Hayakawa, Masato; Shimoyama, Kazuhito; Ara, Kuniaki; Hatakeyama, Nozomu*; Yamauchi, Kanau*; Eda, Yuhei*; Yui, Masahiro*
Nuclear Engineering and Technology, 56(3), p.893 - 899, 2024/03
Times Cited Count：3 Percentile：51.35(Nuclear Science & Technology)Okita, Hidefumi; Tamura, Fumihiko; Yamamoto, Masanobu; Nomura, Masahiro; Shimada, Taihei; Saha, P. K.; Yoshii, Masahito*; Omori, Chihiro*; Sugiyama, Yasuyuki*; Hasegawa, Katsushi*; et al.
Journal of Physics; Conference Series, 2687(7), p.072005_1 - 072005_7, 2024/01
Times Cited Count：0 Percentile：0.00(Physics, Atomic, Molecular & Chemical)Longitudinal phase space tomography is an effective measurement tool for acquiring the longitudinal phase space distribution. For the J-PARC synchrotrons, tomography, which can take into account the beam dynamics such as longitudinal space charge effect and nonlinearity, is desired, as the beam power increases. In this study, for the J-PARC synchrotron, the CERN's tomography, which employs the hybrid algorithm that can consider the beam dynamics for reconstruction, is introduced and benchmarked. The benchmark results show that the CERN's tomography has the ability to measure the longitudinal phase space distribution accurately, in the high-power beam operation at the J-PARC synchrotrons.
Watanabe, Kazuhiko*; Niki, Kazuaki*; Takahashi, Hiroki; Yamamoto, Noboru*; Yoshimoto, Masahiro; Fukuta, Shimpei*
Proceedings of 20th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.844 - 847, 2023/11
J-PARC Personnel Protection System (PPS) acquires and displays data using by PPS Data System. PPS Data System has been using SCADA software, but it has become difficult to handle increased data due to the limited number of signals. Then, it became necessary to build PPS Data System using different software. Therefore, we decided to construct a new system using EPICS, which has been used in the J-PARC control system. On the other hand, PPS is a system that guarantees the safety of personnel, so it cannot be shut down for long periods of time. In addition, it is the most important safety system and must maintain high reliability and stability, so it would be dangerous to update the entire system in a short period of time. Therefore, we decided to divide the PPS Data System by function and replace it with the new system partially while operating the current system. This allows us to verify the operation of the updated parts and correct any problems without compromising the functionality of the PPS, and to construct a new system with high reliability and stability. This presentation will provide an overview of the new system, the updating process, and the progress.
Tamura, Fumihiko; Okita, Hidefumi; Hotchi, Hideaki*; Saha, P. K.; Meigo, Shinichiro; Yoshii, Masahito*; Omori, Chihiro*; Yamamoto, Masanobu; Seiya, Kiyomi*; Sugiyama, Yasuyuki*; et al.
Proceedings of 20th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.64 - 68, 2023/11
The J-PARC 3GeV synchrotron (RCS) provides high intensity proton beams to the Materials and Life Science Experimental Facility (MLF) and the Main Ring (MR). The harmonic number (h) of the RCS is 2 and the RCS normally accelerates two bunches. For some experiments at the MLF, a single bunch is preferred. In this case, one of the rf bucket is filled with protons and the other is empty. Therefore the beam intensity is halved. If the RCS can accelerate with h=1, the intensity per bunch can be doubled, enabling to provide single bunch beams to the MLF with the maximum intensity. This possibly increases the MR beam power by injecting high intensity single bunches eight times. In this presentation, we report mainly on the consideration of h=1 acceleration in the RCS by longitudinal simulations.
Saha, P. K.; Harada, Hiroyuki; Okabe, Kota; Okita, Hidefumi; Shobuda, Yoshihiro; Tamura, Fumihiko; Yamamoto, Kazami; Yoshimoto, Masahiro; Hotchi, Hideaki*
Proceedings of 68th ICFA Advanced Beam Dynamics Workshop on High Intensity and High Brightness Hadron Beams (HB2023) (Internet), p.147 - 152, 2023/10
