Influence of steam flow rate on oxidation kinetics of silicon carbide at 1400-1600 C

Pham, V. H.; Kurata, Masaki; Nagae, Yuji; Ishibashi, Ryo*; Sasaki, Masana*

Corrosion Science, 255, p.113098_1 - 113098_9, 2025/10

https://doi.org/10.1016/j.corsci.2025.113098

Particle arrangements and optical changes induced by the water swelling of melanin-like polydopamine layers

Watanabe, Taku*; Maejima, Yui*; Ueda, Yuki; Motokawa, Ryuhei; Takabatake, Ai*; Takeda, Shinichi*; Fudoji, Hiroshi*; Kishikawa, Keiki*; Koori, Michinari*

Langmuir, 41(34), p.22762 - 22773, 2025/09

https://doi.org/10.1021/acs.langmuir.5c01855

The assembled structures of melanin particles, i.e., colloidal particles coated with a melanin-like polydopamine (PDA) layer, create vivid structural colors. While the thickness of the PDA layer influences the particle arrangement and optical properties, the underlying mechanism has remained controversial. We demonstrate that the waterswelling characteristics of PDA are crucial factors governing the dispersion and aggregation of these particles in solution. Detailed comparisons between dry and wet conditions revealed that the PDA layer readily absorbs water molecules, which leads to significant swelling in the thicker layers. The swelling of the PDA layers determined whether the particles remained dispersed or partially aggregated in the water, ultimately controlling the particle arrangement in the dry state once the water evaporated. These findings provide insights into the self-assembly of colloidal particles and offer a strategy for tuning the periodic particle order. This feature is pivotal for various applications in optical and sensing technologies.

Development of a cooperative operation robot system for radiation source exploration (Contract research); FY2023 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Tohoku University*

JAEA-Review 2025-011, 74 Pages, 2025/08

JAEA-Review-2025-011.pdf:5.31MB

The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Nuclear Energy Science &Z 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 FY2021, this report summarizes the research results of the "Development of a cooperative operation robot system for radiation source exploration" conducted from FY2021 to FY2023. The present study aims to develop a robot system (CORRASE: Cooperative Operation Robot system for RAdiation Source Exploration), realizing radiation source exploration with wide field of view, rapidity, and low cost. In FY2023, our research efforts focused on verification tests for radiation source exploration by summarizing the results of our previous studies. Polyhedral type gamma-ray directional detectors were fabricated from 8 BGO scintillators and shielding bodies. Radiation source exploration experiments were performed by developing a cooperative operation robot system consisting of 3 multi-legged robots carrying the gamma-ray detectors, IMUs (Inertial Measurement Units), and LiDARs (Light Detection And Ranging). An unknown test environment for the radiation source exploration was constructed by placing obstacles and a 10 MBq Cs sealed source as a simulated radioactive contamination source in a room measuring 7.8 5.3 m. The developed system was used to create the environmental map, to formulate the exploration plan, to create the heatmap of the radiation counts, and to image the radiation source from the calculated optimal observation position. The localization of the simulated radioactive contamination source was successfully performed with the cooperation of the 3 robot systems by displaying the image of the radiation source fused on the environmental map. It can be concluded that the initial goal of this study has been successfully achieved by developing the robot system realizing radiation source exploration.

Neutronics/thermal-hydraulics coupling simulation using JAMPAN in a single BWR assembly

Kamiya, Tomohiro; Nagatake, Taku; Ono, Ayako; Tada, Kenichi; Kondo, Ryoichi; Nagaya, Yasunobu; Yoshida, Hiroyuki

Mechanical Engineering Journal (Internet), 12(4), p.24-00461_1 - 24-00461_9, 2025/08

https://doi.org/10.1299/mej.24-00461

JAEA has developed the JAEA Advanced Multi-Physics Analysis platform for Nuclear systems (JAMPAN) to realize high-fidelity neutronics/thermal-hydraulics coupling simulations. We performed a neutronics/thermal-hydraulics coupling simulation for a single BWR fuel assembly in order to confirm that the MVP/JUPITER coupling through JAMPAN is feasible. As a result, we confirmed that the void fraction and the corresponding change in the heat generation distribution are reasonable qualitatively.

Estimation of the beam trip frequency of a proton linear accelerator for an accelerator-driven nuclear transmutation system and comparison with the allowable beam trip frequency

Takei, Hayanori

Journal of Nuclear Science and Technology, 45 Pages, 2025/06

https://doi.org/10.1080/00223131.2025.2523023

The Japan Atomic Energy Agency is working on the research and development of an accelerator-driven nuclear transmutation system (ADS) for transmuting minor actinides. This system combines a subcritical nuclear reactor with a high-power superconducting proton linear accelerator (JADS-linac). One of the factors limiting the advancement of the JADS-linac is beam trips, which often induce thermal cycle fatigue, thereby damaging the components in the subcritical core. The average beam current of the JADS-linac is 32 times higher than that of the linear accelerator (linac) of the Japan Proton Accelerator Research Complex (J-PARC). Therefore, according to the development stage, comparing the beam trip frequency of the JADS-linac with the allowable beam trip frequency (ABTF) is necessary. Herein the beam trip frequency of the JADS-linac was estimated through a Monte Carlo program using the reliability functions based on the operational data of the J-PARC linac. The Monte Carlo program afforded the distribution of the beam trip duration, which cannot be obtained using traditional analytical methods. Results show that the frequency of the beam trips with a duration exceeding 5 min must be reduced to 27% of the current J-PARC linac level to be below the ABTF.

Neutron target for high-intensity operation at J-PARC MLF

Haga, Katsuhiro; Naoe, Takashi; Kogawa, Hiroyuki; Wakui, Takashi; Kinoshita, Hidetaka; Harada, Masahide

Proceedings of 16th International Particle Accelerator Conference (IPAC25) (Internet), p.3245 - 3249, 2025/06

http://dx.doi.org/10.18429/JACoW-IPAC25-FRXD1

In April 2024, the beam power at MLF attained 950 kW for the first time for long term user operation, and the beam power at the 3 GeV rapid cycle synchrotron (RCS) outlet was raised to 1 MW. This accomplishment means that the goal of the stable operation of the neutron source with 1 MW was almost achieved at last, and it's time to go on to the new stage of the neutron source R&D. There are two major challenges for the mercury target in the next stage. One is to attain the long-term operation of a mercury target. The service life of the target vessel is primarily determined by cavitation damage that occurs on the inner surface due to the injection of high-intensity pulsed proton beams. Until now, the vessel has been replaced annually to inspect the extent of the damage. However, based on the damage data obtained during 1 MW high-power operation, it has been determined that the vessel can withstand long-term operation for more than two years. Therefore, a new target vessel, which was replaced in 2024, is scheduled to be used for an extended period through 2027. Furthermore, since there are plans to increase the pulse intensity of the RCS in the future, it will be necessary to develop more effective pitting damage suppression techniques and new target vessels that can withstand even stronger proton beam pulses. In this presentation, the present status of the neutron source of MLF and future operation plans will be shown.

Thermal conductivity evaluation of Am-doped oxide fuels

Yokoyama, Keisuke; Watanabe, Masashi; Onishi, Takashi; Yano, Yasuhide; Tokoro, Daishiro*; Sugata, Hiromasa*; Kato, Masato*

JAEA-Research 2025-002, 18 Pages, 2025/05

JAEA-Research-2025-002.pdf:1.73MB

It is advocated as a development target of fast reactors (FRs) to allow for the of use of mixed oxide (MOX) fuels containing minor actinide (MA) separated and recovered from spent fuels with the aim of reducing the volume and toxicity of high-level radioactive waste generated from nuclear reactors. In the development of MAMOX fuels, it is important behavior to understand the thermal properties such as thermal conductivity for fuel design and analysis of the irradiation. However, there are only a few reports on the thermal properties of MA-MOX fuels, and neither the effects of MA contents nor of oxygen non-stoichiometry in MOX fuels on their thermal conductivities have been fully understood. In this study, the thermal conductivities of MOX fuels with up to 15% Am content were measured at near-stoichiometric composition and the relationship between thermal conductivity and Am content was evaluated. Moreover, the thermal conductivities of Am-doped UO fuels were also measured and evaluated by comparison with Am-MOX to evaluate the effect of Am content. The fuel samples used in this study were three types of MOX with a Pu content of 30% and different Am contents (5%, 10%, and 15%), and UO containing 15% Am. The thermal conductivities of specimens were calculated from the thermal diffusivities measured by the laser flash method, the density of the specimens and, the heat capacity at constant pressure. The oxygen partial pressure during the measurement was controlled at that of the targeted near-stoichiometric composition. The thermal conductivities of all specimens exhibited a decline with increasing temperature and Am content, with a particularly pronounced reduction observed below 1,173 K. The results of the classical phonon scattering model analysis of the measured thermal conductivities showed that the effect of lattice strain due to the Am addition was significant on the thermal resistivity change, and the effect was comparable for both MOX and UO.

Mobile radiation measurement system by multiple small gamma-ray detectors for radioisotope detection and identification supporting responders in the field of nuclear detection and nuclear security

Kimura, Yoshiki; Yamaguchi, Tomoki

Progress in Nuclear Science and Technology (Internet), 7, p.60 - 66, 2025/05

https://doi.org/10.15669/pnst.7.60

Visualization of radioactive contamination around the startup transformer of the Fukushima Daiichi Nuclear Power Station Unit 3 using an integrated radiation imaging system based on a Compton camera

Sato, Yuki; Terasaka, Yuta; Ichiba, Yuta*

Journal of Nuclear Science and Technology, 62(4), p.389 - 400, 2025/04

https://doi.org/10.1080/00223131.2024.2431537

Conceptual study of J-PARC Proton Beam Irradiation Facility

Meigo, Shinichiro; Iwamoto, Hiroki; Sugihara, Kenta*; Hirano, Yukinori*; Tsutsumi, Kazuyoshi*; Saito, Shigeru; Maekawa, Fujio

JAEA-Technology 2024-026, 123 Pages, 2025/03

JAEA-Technology-2024-026.pdf:14.22MB

Based on the design of the ADS Target Test Facility (TEF-T) at the J-PARC Transmutation Experimental Facility, a conceptual study was conducted on the J-PARC proton beam irradiation facility. This research was carried out based on the recommendations of the Nuclear Transmutation Technology Evaluation Task Force of the MEXT. The recommendations state that it is desirable to consider facility specifications that can make the most of the benefits of using the existing J-PARC proton accelerator while also solving the engineering issues of the ADS. We considered facilities that could respond to a variety of needs while reducing the facilities that were not needed in the TEF-T design. In order to clarify these diverse needs, we investigated the usage status of representative accelerator facilities around the world. As a result, it became clear that the main purposes of these facilities were (1) Material irradiation, (2) Soft error testing of semiconductor devices using spallation neutrons, (3) Production of RI for medical use, and (4) Proton beam use, and we investigated the facilities necessary for these purposes. In considering the facility concept, we assumed a user community in 2022 and reflected user opinions in the facility design. This report summarizes the results of the conceptual study of the proton irradiation facility, various needs and responses to them, the roadmap for facility construction, and future issues.