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: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：0CaF: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.
Doda, Norihiro; Kato, Shinya; Uwaba, Tomoyuki; Tanaka, Masaaki; Nakamine, Yoshiaki*; Igawa, Kenichi*; Iida, Masaki*
Proceedings of 21st International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-21) (Internet), 14 Pages, 2025/08
Accurate evaluation of reactivity feedback due to core deformation during power increases in sodium-cooled fast reactors requires comprehensive modeling of the interactions among neutronics, thermal-hydraulics, and core mechanics. To accurately consider these interactions, JAEA has developed an evaluation method that combines multiple analysis codes that model these phenomena in detail. In this study, the evaluation method was applied to the core analysis of the FFTF LOFWOS Test #13, and the analysis results of net reactivity were compared with the test results. The sensitivity analysis results of the core structural design parameters showed that the core bowing behavior has a significant effect on the temporal variation of net reactivity.
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：95.49(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.
Matsuba, Kenichi; Kato, Shinya; Kamiyama, Kenji; Akaev, A. S.*; Vurim, A. D.*; Baklanov, V. V.*
Proceedings of 31st International Conference on Nuclear Engineering (ICONE31) (Internet), 7 Pages, 2024/11
During a severe accident in sodium-cooled fast reactors, molten core materials could be discharged from the core region toward the lower sodium region of the reactor vessel through coolant channels, such as control rod guide tubes. Typical SFRs have a sodium plenum with limited depth and volume, such as the core inlet plenum located under the core region. Therefore, it is important to evaluate the coolability of molten core materials discharged into a depth- and volume-limited sodium plenum. In the present study, to deepen the understanding on the coolability of molten core materials discharged into such a sodium plenum, conditions under which molten core materials form solidified fragments were discussed based on an experiment discharging a molten fuel simulant (molten Al2O3) into a test vessel filled with liquid sodium.
Kabumoto, Hiroshi; Nakamura, Masahiko; Kutsukake, Kenichi; Otokawa, Yoshinori; Asozu, Takuhiro; Matsui, Yutaka; Nakagawa, Sohei; Ikekame, Takuma; Kato, Yuta; Ishizaki, Nobuhiro; et al.
Proceedings of 21st Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1165 - 1169, 2024/10
no abstracts in English
Machida, Masahiko; Yamada, Susumu; Kim, M.; Tanaka, Satoshi*; Tobita, Yasuhiro*; Iwata, Ayako*; Aoki, Yuto; Aoki, Kazuhisa; Yanagisawa, Kenichi*; Yamaguchi, Takashi; et al.
RIST News, (70), p.3 - 22, 2024/09
Inside the Fukushima Daiichi Nuclear Power Plant (1F), there are many locations with high radiation levels due to contamination by radioactive materials that leaked from the reactor. These pose a significant obstacle to the smooth progress of decommissioning work. To help solve this issue, the Japan Atomic Energy Agency (JAEA), under a subsidy from the Ministry of Economy, Trade, and Industry's decommissioning and contaminated water management project, is conducting research and development on digital technologies to improve the radiation environment inside the decommissioning site. This project, titled "Development of Technology to Improve the Environment Inside Reactor Buildings (Enhancing Digital Technology for Environment and Source Distribution to Reduce Radiation Exposure)," began in April of FY 2023. In this project, the aim is to develop three interconnected systems: FrontEnd, Pro, and BackEnd. The FrontEnd system, based on the previously developed 3D-ADRES-Indoor (prototype) from FY 2021-2022, will be upgraded to a high-speed digital twin technology usable on-site. The Pro system will carry out detailed analysis in rooms such as the new office building at 1F, while the BackEnd system will serve as a database to centrally manage the collected and analyzed data. This report focuses on the FrontEnd system, which will be used on-site. After point cloud measurement, the system will quickly create a 3D mesh model, estimate the radiation source from dose rate measurements, and refine the position and intensity of the estimated source using recalculation techniques (re-observation instructions and re-estimation). The results of verification tests conducted on Unit 5 are also presented. Furthermore, the report briefly discusses the future research and development plans for this project.
Matsui, Yutaka; Nakamura, Masahiko; Kutsukake, Kenichi; Kabumoto, Hiroshi; Asozu, Takuhiro; Otokawa, Yoshinori; Ikekame, Takuma; Nakagawa, Sohei; Kato, Yuta; Ishizaki, Nobuhiro; et al.
Dai-36-Kai Tandemu Kasokuki Oyobi Sono Shuhen Gijutsu No Kenkyukai Hokokushu, p.17 - 21, 2024/06
no abstracts in English
Abe, Shinichiro; Hashimoto, Masanori*; Liao, W.*; Kato, Takashi*; Asai, Hiroaki*; Shimbo, Kenichi*; Matsuyama, Hideya*; Sato, Tatsuhiko; Kobayashi, Kazutoshi*; Watanabe, Yukinobu*
IEEE Transactions on Nuclear Science, 70(8, Part 1), p.1652 - 1657, 2023/08
Times Cited Count：7 Percentile：77.55(Engineering, Electrical & Electronic)Single event upsets (SEUs) caused by neutrons is a reliability problem for microelectronic devices in the terrestrial environment. Acceleration tests using white neutron beam provide realistic soft error rates (SERs), but only a few facilities can provide white neutron beam in the world. If single-source irradiation applicable to diverse neutron source can be utilized for the evaluation of the SER in the terrestrial environment, it contributes to solve the shortage of beam time. In this study, we investigated the feasibility of the SER estimation in the terrestrial environment by any one of these measured data with the SEU cross sections obtained by PHITS simulation. It was found that the SERs estimated by our proposed method are within a factor of 2.7 of that estimated by the Weibull function. We also investigated the effect of simplification which reduce the computational cost in simulation to the SER estimation.
Fe
intermetallic compoundCao, Y.*; Zhou, H.*; Khmelevskyi, S.*; Lin, K.*; Avdeev, M.*; Wang, C.-W.*; Wang, B.*; Hu, F.*; Kato, Kenichi*; Hattori, Takanori; et al.
Chemistry of Materials, 35(8), p.3249 - 3255, 2023/04
Times Cited Count：7 Percentile：44.94(Chemistry, Physical)Hydrostatic and chemical pressure are efficient stimuli to alter the crystal structure and are commonly used for tuning electronic and magnetic properties in materials science. However, chemical pressure is difficult to quantify and a clear correspondence between these two types of pressure is still lacking. Here, we study intermetallic candidates for a permanent magnet with a negative thermal expansion (NTE). Based on in situ synchrotron X-ray diffraction, negative chemical pressure is revealed in HoFe on Al doping and quantitatively evaluated by using temperature and pressure dependence of unit cell volume. A combination of magnetization and neutron diffraction measurements also allowed one to compare the effect of chemical pressure on magnetic ordering with that of hydrostatic pressure. Intriguingly, pressure can be used to control suppression and enhancement of NTE. Electronic structure calculations indicate that pressure affected the top of the majority band with respect to the Fermi level, which has implications for the magnetic stability, which in turn plays a critical role in modulating magnetism and NTE. This work presents a good example of understanding the effect of pressure and utilizing it to control properties of functional materials.
Yamamoto, Kazami; Kinsho, Michikazu; Hayashi, Naoki; Saha, P. K.; Tamura, Fumihiko; Yamamoto, Masanobu; Tani, Norio; Takayanagi, Tomohiro; Kamiya, Junichiro; Shobuda, Yoshihiro; et al.
Journal of Nuclear Science and Technology, 59(9), p.1174 - 1205, 2022/09
Times Cited Count：10 Percentile：72.91(Nuclear Science & Technology)In the Japan Proton Accelerator Research Complex, the purpose of the 3 GeV rapid cycling synchrotron (RCS) is to accelerate a 1 MW, high-intensity proton beam. To achieve beam operation at a repetition rate of 25 Hz at high intensities, the RCS was elaborately designed. After starting the RCS operation, we carefully verified the validity of its design and made certain improvements to establish a reliable operation at higher power as possible. Consequently, we demonstrated beam operation at a high power, namely, 1 MW. We then summarized the design, actual performance, and improvements of the RCS to achieve a 1 MW beam.
Matsushita, Hatsuki*; Kobayashi, Ren*; Sakai, Takaaki*; Kato, Shinya; Matsuba, Kenichi; Kamiyama, Kenji
Proceedings of 13th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics, Operation and Safety (NUTHOS-13) (Internet), 9 Pages, 2022/09
During core disruptive accidents in sodium-cooled fast reactors, the molten core material flows through flow channels, such as the control rod guide tubes, into the core inlet plenum under the core region. The molten core material can be cooled and solidified while impinging on a horizontal plate of the inlet plenum in a sodium coolant. However, the solidification and cooling behaviors of molten core materials impinged on a horizontal structure have not been sufficiently studied thus far. Notably, this is an important phenomenon that needs to be elucidated from the perspective of improving the safety of sodium-cooled fast reactors. Accordingly, a series of experiments on discharging a simulated molten core material (alumina: Al
O
) into a sodium coolant on a horizontal structure was conducted at the experimental facility of the National Nuclear Center of the Republic of Kazakhstan. In this study, analyses on the sodium experiments using SIMMER-III as the fast reactor safety evaluation code were performed. The analysis methods were validated by comparing the results and experiment data. In addition, the cooling and solidification behaviors during jet impingement were evaluated. The results indicated that the molten core material exhibited fragmentation owing to the impingement on the horizontal plate and was, therefore, scattered toward the periphery. Furthermore, the simulated molten core material was evaluated to be cooled by sodium and subsequently solidified.
Kato, Shinya; Matsuba, Kenichi; Kamiyama, Kenji; Akaev, A.*; Vurim, A.*; Baklanov, V.*
Proceedings of 13th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics, Operation and Safety (NUTHOS-13) (Internet), 12 Pages, 2022/09
The In-Vessel Retention (IVR) of molten-core in Core Disruptive Accidents (CDAs) is of prime importance in enhancing the safety of sodium-cooled fast reactors. One of the main subjects in ensuring IVR is to design the Control Rod Guide Tube (CRGT) which allows effective discharge of molten core materials from the core region. The effectiveness of the CRGT design is assessed through CDA analyses, and it is reasonable for these analyses to develop a computer code collaborated with experimental researches. Thus, experiments addressing the discharge behavior of the molten-core materials through the CRGT have proceeded as one of the subjects in the collaboration research named the EAGLE-3 project, and the obtained experimental results are reflected in the development of the SIMMER code. In this project, a series of out-of-pile tests using molten-alumina as the fuel simulant was conducted to understand the discharge behavior of molten-core materials through the CRGT. In this study, in order to investigate the effect of an internal structure in the CRGT on the discharge behavior of the molten-core materials, the data of an out-of-pile test in which the molten-alumina penetrated to a duct with the internal structure were analyzed. In addition, the post-test analysis using the SIMMER code was conducted and the results were compared with the test results.
Kamiyama, Kenji; Matsuba, Kenichi; Kato, Shinya; Imaizumi, Yuya; Mukhamedov, N.*; Akayev, A.*; Pakhnits, A.*; Vurim, A.*; Baklanov, V.*
Proceedings of International Conference on Fast Reactors and Related Fuel Cycles; Sustainable Clean Energy for the Future (FR22) (Internet), 9 Pages, 2022/04
Matsuba, Kenichi; Kato, Shinya; Kamiyama, Kenji; Akayev, A. S.*; Baklanov, V. V.*
Proceedings of 28th International Conference on Nuclear Engineering (ICONE 28) (Internet), 4 Pages, 2021/08
In order to obtain experimental knowledge on fragmentation and cooling behavior of molten core material discharged into regions where the depth and volume of sodium are limited, a series of out-of-pile experiments using molten alumina as a simulant for molten core material was conducted. It was found that following mechanisms might be involved in the fragmentation and cooling behavior in a shallow sodium pool: (1) FCI which occurs at location of impingement of the molten jet on the bottom plate promotes fragmentation. (2) If there is a sufficient amount of sodium as a heat sink outside the region, heat exchange by sodium flow in and out due to vapor expansion and condensation suppresses the sodium temperature rise. (3) This temperature suppression contributes to effective cooling of molten core material. In the future study, in order to confirm the mechanisms which was clarified in this study, analytical evaluation of the experimental result will be carried out using a simulation tool.
X raysOkumura, Takuma*; Azuma, Toshiyuki*; Bennet, D. A.*; Caradonna, P.*; Chiu, I. H.*; Doriese, W. B.*; Durkin, M. S.*; Fowler, J. W.*; Gard, J. D.*; Hashimoto, Tadashi; et al.
Physical Review Letters, 127(5), p.053001_1 - 053001_7, 2021/07
Times Cited Count：20 Percentile：76.28(Physics, Multidisciplinary)We observed electronic X rays emitted from muonic iron atoms using a superconducting transition-edge-type sensor microcalorimeter. The energy resolution of 5.2 eV in FWHM allowed us to observe the asymmetric broad profile of the electronic characteristic 
and 
X rays together with the hypersatellite X rays around 6 keV. This signature reflects the time-dependent screening of the nuclear charge by the negative muon and the 
-shell electrons, accompanied by electron side-feeding. Assisted by a simulation, this data clearly reveals the electronic - and -shell hole production and their temporal evolution during the muon cascade process.
Igarashi, Kai*; Onuki, Ryoji*; Sakai, Takaaki*; Kato, Shinya; Matsuba, Kenichi; Kamiyama, Kenji
Proceedings of 2020 International Conference on Nuclear Engineering (ICONE 2020) (Internet), 6 Pages, 2020/08
Kato, Shinya; Matsuba, Kenichi; Kamiyama, Kenji; Ganovichev, D. A.*; Baklanov, V. V.*
Proceedings of 2019 International Congress on Advances in Nuclear Power Plants (ICAPP 2019) (Internet), 9 Pages, 2019/05
In order to ensure In-Vessel Retention (IVR) of molten-core in Core Disruptive Accident (CDA), we are investigating the possibility of the molten-core discharge through the control rod guide tube (CRGT) to prevent energetics due to exceeding the prompt criticality. Internal structures of the CRGT, such as a sodium-flow regulator when the CRGT is connected to the high-pressure plenum, may disturb the discharge of molten-core from the core region. Based on above background, an experimental program to clarify characteristics of molten-core discharge through the CRGT has been commenced as one of subjects under a joint study with National Nuclear Center of the Republic of Kazakhstan (NNC-RK) named EAGLE-3 project. An experiment using molten-alumina as fuel simulant and sodium was conducted at the out-of-pile test facility owned by NNC-RK to investigate sodium cooling effect around the sodium flow regulator on its destruction. The experimental result represented that void development at the initiation of molten-alumina discharge eliminated liquid-phase sodium from the discharge path and this also eliminated sodium cooling effect around the sodium flow regulator. As a result, early destruction of the sodium flow regulator and massive discharge of molten alumina occurred in turn.
Okabe, Kota; Yamamoto, Kazami; Kamiya, Junichiro; Takayanagi, Tomohiro; Yamamoto, Masanobu; Yoshimoto, Masahiro; Takeda, Osamu*; Horino, Koki*; Ueno, Tomoaki*; Yanagibashi, Toru*; et al.
Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.853 - 857, 2017/12
The most important issue is to reduce the uncontrolled beam loss in the high intensity hadron accelerator such as J-PARC proton accelerators. The J-PARC 3 GeV Synchrotron (RCS) has a collimator system which narrows a high intensity beam in the RCS. After startup of RCS in 2007, the collimator system of the RCS worked well. However, in April 2016, vacuum leakage at the collimator system occurred during the maintenance operation. To investigate a cause of the failure, we took apart iron shields of the collimator reducing exposed dose of operators. As a result of inspection, we succeeded to identify the cause of the vacuum leakage failure. In this presentation, we report the failure investigation of the beam collimator system in the RCS.
Shimomura, Kenta; Kato, Shoichi; Wakai, Takashi; Ando, Masanori; Hirose, Yuichi*; Sato, Kenichiro*
Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 9 Pages, 2015/05
This paper describes experimental and analytical works to confirm that the design standard for SFR components sufficiently covers possible failure mechanisms. Creep-fatigue damage evaluation method in JSME design standard for SFR components has been constructed based on experiments and/or numerical analyses of conventional austenitic stainless steels, such as 304SS. Since the material characteristics of Mod.9Cr-1Mo steel are substantially different from those of austenitic stainless steels, it is required to verify the applicability of the design standards to the SFR components made of Mod.9Cr-1Mo steel. A series of uni-axial creep-fatigue tests were conducted using double-ended notch bar specimens made of Mod.9Cr-1Mo steel under displacement controlled condition with 30 minute holding. The curvature radii of the specimens were 1.6mm, 11.2mm and 40.0mm. The specimen having 1.6mm notch and 11.2mm notch failed from outer surface but the specimen having 40.0mm notch showed obvious internal crack nucleation. In addition, though total duration time of the creep-fatigue test was only 2,000 hours, a lot of creep voids and inter granular crack growth were observed. To clarify the cause of such peculiar failure, some additional experiments were performed, as well as some numerical analyses. We could point out that such a peculiar failure aspect might result from corresponding stress distribution in the cross section. As a result of a series of investigations, possible causes of such peculiar failure could be narrowed down. A future investigation plan was proposed to clarify the most significant cause.
Kim, J.*; Fujiwara, Akihiko*; Sawada, Tomohiro*; Kim, Y.*; Sugimoto, Kunihisa*; Kato, Kenichi*; Tanaka, Hiroshi*; Ishikado, Motoyuki*; Shamoto, Shinichi; Takata, Masaki*
IUCrJ, 1(3), p.155 - 159, 2014/05
Times Cited Count：3 Percentile：27.61(Chemistry, Multidisciplinary)Using a charge density analysis based on synchrotron radiation X-ray powder diffraction data, we found that the charge carriers only accumulated in the iron layer of the superconducting phase of LaFeAsO
F
at low temperatures. Analysis of the electrostatic potential distribution revealed the concerted enhancement of the electronic polarization of the As ions and the carrier redistribution.
