Sato, Yosuke*; Sekiyama, Tsuyoshi*; Fang, S.*; Kajino, Mizuo*; Qurel, A.*; Qulo, D.*; Kondo, Hiroaki*; Terada, Hiroaki; Kadowaki, Masanao; Takigawa, Masayuki*; et al.
Atmospheric Environment; X (Internet), 7, p.100086_1 - 100086_12, 2020/10
The third model intercomparison project for investigating the atmospheric behavior of Cs emitted during the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident (FDNPP-MIP) was conducted. A finer horizontal grid spacing (1 km) was used than in the previous FDNPP-MIP. Nine of the models used in the previous FDNPP-MIP were also used, and all models used identical source terms and meteorological fields. Our analyses indicated that most of the observed high atmospheric Cs concentrations were well simulated, and the good performance of some models improved the performance of the multi-model ensemble. The analyses also confirmed that the use of a finer grid resolution resulted in the meteorological field near FDNPP being better reproduced. The good representation of the wind field resulted in the reasonable simulation of the narrow distribution of high deposition amount to the northwest of FDNPP and the reduction of the overestimation over the area to the south of FDNPP. In contrast, the performance of the models in simulating plumes observed over the Nakadori area, the northern part of Gunma, and the Tokyo metropolitan area was slightly worse.
Furutani, Misa; Kometani, Tatsunari; Nakagawa, Masahiro; Ueno, Yumi; Sato, Junya; Iwai, Yasunori*
Hoken Butsuri (Internet), 55(2), p.97 - 101, 2020/06
Herein, an oxidation catalyst was introduced after heating it to 600C to oxidize tritium gas (HT) existing in exhaust into tritiated water vapor (HTO). This study aims to establish a safer H monitoring system by lowering the heating temperature required for the catalyst. In these experiments, which were conducted in the Nuclear Science Research Institute, Japan Atomic Energy Agency, cupric oxide, hydrophobic palladium/silicon dioxide (Pd/SiO), and platinum/aluminum oxide (Pt/AlO) catalysts were ventilated using standard hydrogen gas. After comparing the oxidation efficiency of each catalyst at different temperatures, we found that the hydrophobic Pd/SiO and Pt/AlO catalysts could oxidize HT into HTO at 25C.
Abe, Shinichiro; Sato, Tatsuhiko; Kuroda, Junya*; Manabe, Seiya*; Watanabe, Yukinobu*; Liao, W.*; Ito, Kojiro*; Hashimoto, Masanori*; Harada, Masahide; Oikawa, Kenichi; et al.
Proceedings of IEEE International Reliability Physics Symposium (IRPS 2020) (Internet), 6 Pages, 2020/04
Single event upsets (SEUs) caused by neutrons have been recognized as a serious reliability problem for microelectronic devices on the ground level. In our previous work, it was found that hydride placed in front of the memory chip has considerably impact on SEU cross sections because H ions generated via elastic scattering of neutrons with hydrogen atoms are only emitted in a forward direction. In this study, the effect of components neighboring transistors on neutron-induced SEUs was investigated for 65-nm bulk SRAMs by using PHITS. It was found that the shape of the SEU cross section around few MeV comes from the thickness and the position of components placed in front of transistors when that components do not contains hydrogen atoms. By considering components adjoin memory cells in the test board used in the simulation, measured data at J-PARC BL10 were reproduced well. In addition, it was found that the effect of components neighboring transistors on neutron-induced SERs does not negligible in terrestrial environment.
Sato, Junya; Shiota, Kenji*; Takaoka, Masaki*
Journal of Hazardous Materials, 385, p.121109_1 - 121109_9, 2020/03
Lead is a hazardous heavy metal that can be stabilized by incorporation into the matrix of aluminosilicate bearing phases as they solidify. The actual mechanism by which lead is stabilized, however, continues to be unclear because the individual mechanisms of Pb incorporation into crystalline and amorphous aluminosilicate phases have not yet been studied separately. A detailed investigation of the incorporation of Pb into the amorphous phase of aluminosilicate solids was therefore performed. Amorphous aluminosilicate solids were synthesized with 0.7, 1.5, and 3.7 wt% of Pb from aluminosilicate gel produced from chemical reagents. Based on Raman spectroscopy, the Si-O stretching vibration bond shifted to lower wavenumbers with increasing Pb concentration. This shift suggested that covalent bonding between Pb and O in the matrix of the aluminosilicate solids increased. In addition, sequential extraction revealed that most of the Pb (75-90%) in the aluminosilicate solids was in a poorly soluble form (i.e. reducible, oxidizable, and residual fractions). These findings indicate that most of Pb is bonded covalently to the amorphous phase in aluminosilicate solids.
Kim, S. H.*; Ichikawa, Yudai; Sako, Hiroyuki; Hasegawa, Shoichi; Hayakawa, Shuhei*; Nanamura, Takuya*; Sato, Susumu; Tanida, Kiyoshi; Yoshida, Junya; 11 iof others*
Nuclear Instruments and Methods in Physics Research A, 940, p.359 - 370, 2019/10
Ekawa, Hiroyuki; Ashikaga, Sakiko; Hasegawa, Shoichi; Hashimoto, Tadashi; Hayakawa, Shuhei; Hosomi, Kenji; Ichikawa, Yudai; Imai, Kenichi; Kimbara, Shinji*; Nanamura, Takuya; et al.
Progress of Theoretical and Experimental Physics (Internet), 2019(2), p.021D02_1 - 021D02_11, 2019/02
Sato, Yosuke*; Takigawa, Masayuki*; Sekiyama, Tsuyoshi*; Kajino, Mizuo*; Terada, Hiroaki; Nagai, Haruyasu; Kondo, Hiroaki*; Uchida, Junya*; Goto, Daisuke*; Qulo, D.*; et al.
Journal of Geophysical Research; Atmospheres, 123(20), p.11748 - 11765, 2018/10
A model intercomparison of the atmospheric dispersion of Cs emitted following the Fukushima Daiichi Nuclear Power Plant accident was conducted by 12 models to understand the behavior of Cs in the atmosphere. The same meteorological data, horizontal grid resolution, and an emission inventory were applied to all the models to focus on the model variability originating from the processes included in each model. The multi-model ensemble captured 40% of the observed Cs events, and the figure-of-merit in space for the total deposition of Cs exceeded 80. Our analyses indicated that the meteorological data were most critical for reproducing the Cs events. The results also revealed that the differences among the models were originated from the deposition and diffusion processes when the meteorological field was simulated well. However, the models with strong diffusion tended to overestimate the Cs concentrations.
Humrickhouse, P. W.*; Sato, Hiroyuki; Imai, Yoshiyuki; Sumita, Junya; Yan, X. L.
Proceedings of 9th International Topical Meeting on High Temperature Reactor Technology (HTR 2018) (USB Flash Drive), 9 Pages, 2018/10
This work describes the development of a RELAP5-3D model of the HTTR-GT/H plant secondary system. The RELAP5-3D model presently includes detailed models of several of the heat exchangers in the secondary system as well as the turbomachinery, which includes two compressors and two gas turbines connected to a common shaft and motor. The predictions of the model agreed well to design parameters in both sole power generation and hydrogen co-generation modes in most instances. Both the turbomachinery and heat exchanger models rely on extensive customization via RELAP5-3D control variables, and these implementations are outlined in detail. Potential improvements to the RELAP5-3D turbine model are discussed.
Sato, Hiroyuki; Nomoto, Yasunobu*; Horii, Shoichi*; Sumita, Junya; Yan, X.
Nuclear Engineering and Design, 329, p.247 - 254, 2018/04
This paper presents the system performance evaluation for HTTR gas turbine cogeneration test plant (HTTR-GT/H plant) so as to confirm that the design meets the requirements with respect to the demonstration test objective. Start-up and shut down operation sequences as well as operability of load following operation were investigated. In addition, system dynamic and control analyses for the test plant in the events of loss of generator load and upset of H plant were performed. The simulation results presented in the paper show that the test plant is suitable for the test bed to validate control schemes against postulated transients in the GTHTR300C. The results also lead us to the conclusion that HTTR-GT/H plant can be used to test operational procedures unique to HTGR direct-cycle gas turbine cogeneration.
Yan, X. L.; Sato, Hiroyuki; Sumita, Junya; Nomoto, Yasunobu*; Horii, Shoichi*; Imai, Yoshiyuki; Kasahara, Seiji; Suzuki, Koichi*; Iwatsuki, Jin; Terada, Atsuhiko; et al.
Nuclear Engineering and Design, 329, p.223 - 233, 2018/04
The pre-licensing design of an HTGR cogeneration test plant to be coupled to JAEA's existing test reactor HTTR is presented. The plant is designed to demonstrate the system of JAEA commercial plant design GTHTR300C. With construction planned to be completed around 2025, the test plant is expected to be the first-of-a-kind nuclear system operating on two of the advanced energy conversion systems attractive for the HTGR closed cycle helium gas turbine for power generation and thermochemical iodine-sulfur water-splitting process for hydrogen production.
Sato, Junya; Kikuchi, Hiroshi*; Kato, Jun; Sakakibara, Tetsuro; Matsushima, Ryotatsu; Sato, Fuminori; Kojima, Junji; Nakazawa, Osamu
QST-M-8; QST Takasaki Annual Report 2016, P. 62, 2018/03
no abstracts in English
Nomoto, Yasunobu; Horii, Shoichi; Sumita, Junya; Sato, Hiroyuki; Yan, X.
Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 9 Pages, 2017/04
This paper presents the cost performance design of heat transport piping systems for GTHTR300C plant and HTTR-GT/H plant. Two types of pipe structure are designed and compared in terms of cost performance. Relative to the coaxial double-pipe structure, the insulated single pipe structure is found to have the advantage in overall cost performance considering both the material quantity and the heat loss because it reduces the quantity of steel used for construction. Furthermore it is possible to reduce the heat loss and temperature reduction of hot helium gas by the attachment of the external insulation. The pressure tube made of type-316 stainless steel with high-temperature strength is possible to achieve the same temperature reduction by smaller diameter than that made of 2 1/4Cr-1Mo steel. It contributes to the reduction of the quantity of steel. Specifications of heat transport piping systems for both plants are determined according to these study results.
Sato, Junya; Suzuki, Shinji*; Kato, Jun; Sakakibara, Tetsuro; Meguro, Yoshihiro; Nakazawa, Osamu
QST-M-2; QST Takasaki Annual Report 2015, P. 87, 2017/03
no abstracts in English
Sato, Junya; Suzuki, Shinji*; Kato, Jun; Sakakibara, Tetsuro; Meguro, Yoshihiro; Nakazawa, Osamu
QST-M-2; QST Takasaki Annual Report 2015, P. 88, 2017/03
no abstracts in English
Sato, Hiroyuki; Nomoto, Yasunobu; Horii, Shoichi; Sumita, Junya; Yan, X.; Ohashi, Hirofumi
Proceedings of 8th International Topical Meeting on High Temperature Reactor Technology (HTR 2016) (CD-ROM), p.759 - 766, 2016/11
This paper presents the system performance evaluation for HTTR gas turbine cogeneration test plant (HTTR-GT/H plant) so as to confirm that the design meets the requirements with respect to the demonstration test objective. Start-up and shut down operation sequences as well as operability of load following operation were investigated. In addition, system dynamic and control analyses for the test plant in the events of loss of generator load and upset of H plant were performed. The simulation results presented in the paper show that the test plant is suitable for the test bed to validate control schemes against postulated transients in the commercial Gas Turbine High Temperature Reactor Cogeneration (GTHTR300C). The results also lead us to the conclusion that HTTR-GT/H plant can be used to test operational procedure unique to HTGR direct-cycle gas turbine cogeneration.
Yan, X.; Sato, Hiroyuki; Sumita, Junya; Nomoto, Yasunobu; Horii, Shoichi; Imai, Yoshiyuki; Kasahara, Seiji; Suzuki, Koichi*; Iwatsuki, Jin; Terada, Atsuhiko; et al.
Proceedings of 8th International Topical Meeting on High Temperature Reactor Technology (HTR 2016) (CD-ROM), p.827 - 836, 2016/11
Pre-licensing basic design for a cogenerating HTGR test plant system is presented. The plant to be coupled to existing 30 MWt 950C test reactor HTTR is intended as a system technology demonstrator for GTHTR300C plant design. More specifically the test plant of HTTR-GT/H aims to (1)demonstrate the licensability of the GTHTR300C for electricity production by gas turbine and hydrogen cogeneration by thermochemical process and (2) confirm the operation control and safety of such cogeneration system. With construction and operation completion by 2025, the test plant is expected to be the first of a kind HTGR-powered cogeneration plant operating on the two advanced energy conversion systems of closed cycle helium gas turbine for power generation and thermochemical iodine-sulfur water-splitting process for hydrogen production.
Meguro, Yoshihiro; Nakagawa, Akinori; Kato, Jun; Sato, Junya; Nakazawa, Osamu; Ashida, Takashi
Proceedings of International Conference on the Safety of Radioactive Waste Management (Internet), p.139_1 - 139_4, 2016/11
A variety of radioactive wastes have been generated in decommissioning of Fukushima Daiichi Nuclear Power Station. It is necessary to evaluate feasibility of conditioning methods to these wastes, because the majority of such wastes have not been solidified in Japan. The authors investigated an approach for screening of conditioning methods for the Fukushima wastes on the basis of the findings of the existing methods and results of fundamental solidification tests using synthetic Fukushima wastes. Here five solidification methods were selected, and also 13 wastes with different chemical composition are solidified, and characteristics of the solidified form are studied. A screening flow was proposed, and evaluation criteria on each step in the flow was set up. In this presentation a trial result was opened for a waste and improvements of the screening flow found in the trial evaluation was described.
Meguro, Yoshihiro; Sato, Junya
Dekomisshoningu Giho, (54), p.48 - 55, 2016/09
Various radioactive wastes, especially liquiform, pulverized or grained one, have to be immobilized in a disposal container, and methods such as cement solidification, bituminization, etc are so far examined and have been adopted. In recent years novel inorganic solidification materials have been developed. These are named Alkali-activated materials and so geopolymer. Mainly studies of geopolymer applying to radioactive wastes as a solidification material are under research and development stage, but the cases applied to solidification of the real radioactive waste increase a lot. In this report, we briefly explain about some research studies and practical examples of the geopolymer in the field of nuclear energy, particularly those of radioactive wastes generated in Fukushima Daiichi Nuclear Power Station.
Sato, Hiroyuki; Yan, X.; Sumita, Junya; Terada, Atsuhiko; Tachibana, Yukio
Journal of Nuclear Engineering and Radiation Science, 2(3), p.031010_1 - 031010_6, 2016/07
This paper explains the outline of HTTR demonstration program with a plant concept of the heat application system directed at establishing an HTGR cogeneration system with 950C reactor outlet temperature for production of power and hydrogen as recommended by the task force. Commercial deployment strategy including a development plan for the helium gas turbine is also presented.
Ueno, Yumi; Nakagawa, Masahiro; Sato, Junya; Iwai, Yasunori
Hoken Butsuri, 51(1), p.7 - 11, 2016/03
In the Nuclear Science Research Institute, Japan Atomic Energy Agency (JAEA), in order to oxidize C, which exists in various chemical forms in exhaust, into CO, a copper oxide (CuO) catalyst is introduced after heating to 600C. Our goal was to establish a safer C monitoring system by lowering the heating temperature required for the catalyst; therefore, we developed a new hydrophobic palladium/silicon dioxide (Pd/SiO) catalyst that makes the carrier's surface hydrophobic. In these experiments, catalysts CuO, platinum/aluminum oxide (Pt/AlO), palladium/zirconium dioxide (Pd/ZrO), hydrophobic Pd/SiO, and hydrophilic Pd/SiO were ventilated with standard methane gas, and we compared the oxidation efficiency of each catalyst at different temperatures. As a result, we determined that the hydrophobic Pd/SiO catalyst had the best oxidation efficiency. By substituting the currently used CuO catalyst with the hydrophobic Pd/SiO catalyst, we will be able to lower the working temperature from 600C to 300C and improve the safety of the monitoring process.