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Yoshimune, Wataru*; Higuchi, Yuki*; Kato, Akihiko*; Hibi, Shogo*; Yamaguchi, Satoshi*; Matsumoto, Yoshihiro*; Hayashida, Hirotoshi*; Nozaki, Hiroshi*; Shinohara, Takenao; Kato, Satoru*
ACS Energy Letters (Internet), 8(8), p.3485 - 3487, 2023/08
Times Cited Count:3 Percentile:66.84(Chemistry, Physical)Hashimoto, Shunsuke*; Yamaguchi, Satoshi*; Harada, Masashi*; Nakajima, Kenji; Kikuchi, Tatsuya*; Oishi, Kazuki*
Journal of Colloid and Interface Science, 638, p.475 - 486, 2023/05
Times Cited Count:2 Percentile:60.61(Chemistry, Physical)Recently, it has been reported that anomalous improvement in the thermal conductivity of nanofluid composed of base liquids and dispersed solid nanoparticles, compared to the theoretically predicted value calculated from the particle fraction. Generally, the thermal conductivity values of gases and liquids are dominated by the mean free path of the molecules during translational motion. Herein, we present solid evidence showing the possible contribution of the vibrational behavior of liquid molecules around nanoparticles to increasing these thermal conductivities.
Nakamura, Satoshi*; Hosaka, Atsushi; Yamaguchi, Yasuhiro
Physical Review D, 104(9), p.L091503_1 - L091503_8, 2021/11
Times Cited Count:17 Percentile:80.09(Astronomy & Astrophysics)Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Takagi, Yasuhiko*; Nakamura, Tomoki*; Hiroi, Takahiro*; Matsuoka, Moe*; et al.
Nature Astronomy (Internet), 5(3), p.246 - 250, 2021/03
Times Cited Count:44 Percentile:97.1(Astronomy & Astrophysics)Here we report observations of Ryugu's subsurface material by the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft. Reflectance spectra of excavated material exhibit a hydroxyl (OH) absorption feature that is slightly stronger and peak-shifted compared with that observed for the surface, indicating that space weathering and/or radiative heating have caused subtle spectral changes in the uppermost surface. However, the strength and shape of the OH feature still suggests that the subsurface material experienced heating above 300 C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 C at the estimated excavation depth of 1 m, even if the semimajor axis is reduced to 0.344 au. This supports the hypothesis that primary thermal alteration occurred due to radiogenic and/or impact heating on Ryugu's parent body.
Nagao, Fumiya; Niizato, Tadafumi; Sasaki, Yoshito; Ito, Satomi; Watanabe, Takayoshi; Dohi, Terumi; Nakanishi, Takahiro; Sakuma, Kazuyuki; Hagiwara, Hiroki; Funaki, Hironori; et al.
JAEA-Research 2020-007, 249 Pages, 2020/10
The accident of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. occurred due to the Great East Japan Earthquake, Sanriku offshore earthquake, of 9.0 magnitude and the accompanying tsunami. As a result, large amount of radioactive materials was released into the environment. Under these circumstances, Japan Atomic Energy Agency (JAEA) has been conducting "Long-term Assessment of Transport of Radioactive Contaminants in the Environment of Fukushima" concerning radioactive materials released in environment, especially migration behavior of radioactive cesium since November 2012. This report is a summary of the research results that have been obtained in environmental dynamics research conducted by JAEA in Fukushima Prefecture.
Nagao, Fumiya; Niizato, Tadafumi; Sasaki, Yoshito; Ito, Satomi; Watanabe, Takayoshi; Dohi, Terumi; Nakanishi, Takahiro; Sakuma, Kazuyuki; Hagiwara, Hiroki; Funaki, Hironori; et al.
JAEA-Research 2019-002, 235 Pages, 2019/08
The accident of the Fukushima Daiichi Nuclear Power Station (hereinafter referred to 1F), Tokyo Electric Power Company Holdings, Inc. occurred due to the Great East Japan Earthquake, Sanriku offshore earthquake, of 9.0 magnitude and the accompanying tsunami. As a result, large amount of radioactive materials was released into the environment. Under these circumstances, JAEA has been conducting Long-term Environmental Dynamics Research concerning radioactive materials released in environment, especially migration behavior of radioactive cesium since November 2012. This report is a summary of the research results that have been obtained in environmental dynamics research conducted by JAEA in Fukushima Prefecture.
Kogure, Toshihiro*; Yamaguchi, Noriko*; Segawa, Hiroyo*; Mukai, Hiroki*; Motai, Satoko*; Akiyama, Kotone*; Mitome, Masanori*; Hara, Toru*; Yaita, Tsuyoshi
Microscopy, 65(5), p.451 - 459, 2016/10
Times Cited Count:54 Percentile:96.98(Microscopy)Yamamoto, Seiichi*; Toshito, Toshiyuki*; Komori, Masataka*; Morishita, Yuki*; Okumura, Satoshi*; Yamaguchi, Mitsutaka; Saito, Yuichi; Kawachi, Naoki; Fujimaki, Shu
Annals of Nuclear Medicine, 29(3), p.268 - 275, 2015/04
Times Cited Count:21 Percentile:67.44(Radiology, Nuclear Medicine & Medical Imaging)Kurisaka, Kenichi; Sakai, Takaaki; Yamano, Hidemasa; Fujita, Satoshi*; Minagawa, Keisuke*; Yamaguchi, Akira*; Takata, Takashi*
Nuclear Engineering and Design, 269, p.268 - 280, 2014/04
Times Cited Count:5 Percentile:36.8(Nuclear Science & Technology)This paper describes a study to develop the level-1 probabilistic safety assessment (PSA) method that is applicable to the Japan Sodium-cooled Fast Reactor (JSFR). This study aims to provide a new evaluation method of (1) passive safety architectures related to internal events and (2) an advanced seismic isolation system related to a seismic event as a representative external event in Japan. Regarding the internal events evaluation, a quantitative analysis on the frequency of the core damage caused by reactor shutdown failure was conducted. A failure in passive reactor shutdown was taken into account in the event tree model. The failure rate of sodium-cooled fast reactor (SFR) specific components was evaluated based on the operating experience in existing SFRs by applying the Hierarchical Bayesian Method, which can consider a plant-to-plant variability. By conducting an uncertainty analysis, it was found that the assumption about the correlation of the probability parameters between the main and backup reactor shutdown systems is sensitive to the mean value of the frequency of the core damage caused by reactor shutdown failure. As for the seismic event evaluation, seismic response analysis and sensitivity analysis of a seismic isolation system were carried out. As a result, it was confirmed that nonlinear properties of rubber bearings have influence on response of the building and inner equipment.
Minagawa, Keisuke*; Fujita, Satoshi*; Yamaguchi, Akira*; Takata, Takashi*; Kurisaka, Kenichi
Nihon Kikai Gakkai Rombunshu, C, 79(804), p.2684 - 2693, 2013/08
Minagawa, Keisuke*; Fujita, Satoshi*; Yamaguchi, Akira*; Takata, Takashi*; Kurisaka, Kenichi
Transactions of the 22nd International Conference on Structural Mechanics in Reactor Technology (SMiRT-22) (CD-ROM), 9 Pages, 2013/08
Application of seismic isolation system using rubber bearings into nuclear power plants has been expected. Generally, rubber bearings have nonlinear characteristics in case of large deformation. In addition, the horizontal nonlinear characteristics depend on vertical load. Therefore it is important to consider these nonlinearity and coupling effect. Authors have already reported results of seismic response analysis of an isolated reactor building considering the nonlinearity of rubber bearings. In this paper, seismic response analysis considering the coupling effect of horizontal and vertical deformation of rubber bearings is investigated by numerical simulations. The summaries of the simulations are as follows. The vertical motion affected the start displacement of hardening, so that the coupling effect decreased isolation performance of horizontal direction. However the isolation system is still effective to reduce seismic force even if the nonlinearity and the coupling effect were considered.
Kurisaka, Kenichi; Sakai, Takaaki; Yamano, Hidemasa; Nishino, Hiroyuki; Fujita, Satoshi*; Minagawa, Keisuke*; Yamaguchi, Akira*; Takata, Takashi*
Proceedings of Probabilistic Safety Assessment and Management Topical Conference; In light of the Fukushima Dai-ichi Accident (PSAM 2013) (USB Flash Drive), 10 Pages, 2013/04
This study includes a level-1 PSA related to internal events and a seismic event as a representative external event for Japan sodium-cooled fast reactors with passive safety features and a seismic isolation system. For the internal events, it is necessary to evaluate the passive safety features, of which reliability depends on uncertainties of related physical phenomena. In order to consider the reliability of the passive natural circulation, accident sequences leading to core damage result from natural circulation failure were developed, and the annual frequency of the accident sequences was evaluated for the PSA method study. In respects of seismic event, we developed response analysis method considering the coupling effect of horizontal and vertical shaking on the horizontal seismic isolation characteristics, and developed a fragility evaluation model including the effect of seismic non-linearly for the seismic isolation system.
Fujita, Satoshi*; Minagawa, Keisuke*; Yamaguchi, Akira*; Takata, Takashi*; Kurisaka, Kenichi
Proceedings of 15th World Conference on Earthquake Engineering (WCEE-15) (USB Flash Drive), 9 Pages, 2012/09
Kurisaka, Kenichi; Sakai, Takaaki; Yamano, Hidemasa; Fujita, Satoshi*; Minagawa, Keisuke*; Yamaguchi, Akira*; Takata, Takashi*
Transactions of the 21st International Conference on Structural Mechanics in Reactor Technology (SMiRT-21) (CD-ROM), 8 Pages, 2011/11
This paper describes a study to develop the level-1 probabilistic safety assessment (PSA) method that is applicable to the Japan Sodium-cooled Fast Reactor (JSFR). This study has been started since August 2010 and aims to provide a new evaluation method of (1) passive safety architectures related to internal events and (2) an advanced seismic isolation system related to a seismic event as a representative external event in Japan. However, after the nuclear accident at Fukushima Dai-ichi Nuclear Power Plant on March 11 2011, the research-period was shortened from four to two years by political reason, and only a limited scope of the research subject will be performed in the two years. Regarding the internal events evaluation, a quantitative analysis on the frequency of the core damage caused by reactor shutdown failure was conducted. A failure in passive reactor shutdown was taken into account in the event tree model. The failure rate of sodium-cooled fast reactor (SFR) specific components was evaluated based on the operating experience in existing SFRs by applying the Hierarchical Bayesian Method, which can consider a plant-to-plant variability. By conducting an uncertainty analysis, it was found that the assumption about the correlation of the probability parameters between the main and backup reactor shutdown systems is sensitive to the mean value of the frequency of the core damage caused by reactor shutdown failure.
Minagawa, Keisuke*; Fujita, Satoshi*; Yamaguchi, Akira*; Takata, Takashi*; Kurisaka, Kenichi
Transactions of the 21st International Conference on Structural Mechanics in Reactor Technology (SMiRT-21) (CD-ROM), 8 Pages, 2011/11
We carried out fundamental seismic response analysis that considers both horizontal and vertical nonlinearity of rubber bearing. In this study, the horizontal nonlinearity was considered independently from vertical response in order to construct accurate nonlinear analytical model of rubber bearing. That is to say, the coupling effect was not considered. Both horizontal and vertical nonlinear characteristics of rubber bearing were explained by multi-linear model. Analytical model of building for horizontal direction consists of 3 mass points that is the isolation layer, lower and upper layer of the building. It for vertical direction consists of 4 mass points, that is ground layer, the isolation layer, lower and upper layer of the building. At first, nonlinear seismic response analysis was executed in order to confirm nonlinear characteristics of analytical model of rubber bearing. Influence of nonlinearity of rubber bearing upon response of building was also investigated by the analysis. After that, sensitivity analysis was executed. Parameters of rubber bearing, oil damper and building were fluctuated, and influence of variation of these parameters upon response of building was investigated.
Fujita, Satoshi*; Minagawa, Keisuke*; Yamaguchi, Akira*; Takata, Takashi*; Kurisaka, Kenichi
Dynamics and Design Conference 2011 (D&D 2011) Koen Rombunshu (CD-ROM), 7 Pages, 2011/09
The response to the input more than assumption is requested in the seismic response analysis used for the Probabilistic Safety Assessment. Rubber bearings used as the isolation system cause nonlinearity in the restoring force when the input more than assumption is received. However, the seismic response analysis method for considering nonlinear of the rubber bearing has not been established. Therefore, this study aims at the development of the seismic response analysis method of an isolated nuclear power plant based on the probabilistic safety assessment. In this paper, isolated building model that the nonlinearity of the rubber bearing is considered is made, the seismic response analysis is done, and the influence that it gives respond was verified. As a result, in horizontal direction, it was confirmed that the increasing tendency of the response acceleration was remarkable because of the increase of the earthquake size. In vertical direction, it was confirmed that the increasing tendency of the response displacement was remarkable.
Minagawa, Keisuke*; Fujita, Satoshi*; Yamaguchi, Akira*; Takata, Takashi*; Kurisaka, Kenichi
Dynamics and Design Conference 2011 (D&D 2011) Koen Rombunshu (CD-ROM), 10 Pages, 2011/09
It is necessary to consider the change in the response by the difference of the physical properties value and the material characterizations of an isolation layer and a building in Probabilistic Safety Assessment. Then, in this paper, the sensitivity analysis of the parameter of the isolated building model that the nonlinearity of rubber bearing is considered used for the seismic response analysis done by the first report is done. The response when an arbitrary parameter is set to the upper limit or the lower limit by the logarithm standard deviation is compared with the response when all parameters are set to the median, and the error ratio is examined as sensitivity. As a result, in the earthquake size in which the nonlinearity is caused, the difference of the parameter of the building, the isolation layer such as the displacement that hardening begins and the load that softening begins of the rubber bearing shows high sensitivity, and it has a bad influence for the building response. Therefore, it was confirmed that the parameter that showed high sensitivity had to examine the difference in detail.
Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Yasuyuki*; Al-Bataineh, H.*; Alexander, J.*; Aoki, Kazuya*; Aphecetche, L.*; Aramaki, Y.*; et al.
Physical Review C, 83(4), p.044912_1 - 044912_16, 2011/04
Times Cited Count:9 Percentile:49.6(Physics, Nuclear)Measurements of electrons from the decay of open-heavy-flavor mesons have shown that the yields are suppressed in Au+Au collisions compared to expectations from binary-scaled collisions. Here we extend these studies to two particle correlations where one particle is an electron from the decay of a heavy flavor meson and the other is a charged hadron from either the decay of the heavy meson or from jet fragmentation. These measurements provide more detailed information about the interaction between heavy quarks and the quark-gluon matter. We find the away-side-jet shape and yield to be modified in Au+Au collisions compared to collisions.
Takamine, Jun; Haruyama, Mitsuo; Takase, Misao; Yamaguchi, Satoshi
Proceedings of 16th Pacific Basin Nuclear Conference (PBNC-16) (CD-ROM), 6 Pages, 2008/10
When an object including a lot of hydrogen atoms such as the cemented waste is measured by using the conventional active neutron method, radial sensitivity distribution in the region of surface and center is different more than 100 times. Then we developed the method to detect a nuclear fission neutron induced by the neutron which slowed down in the matrix itself, and so performed a position sensitivity difference of 10%. Furthermore, we understood that the background neutron in nuclear fission neutron counting area is great decrease by using SUS-304 instead of graphite as a moderator of conventional detection system. And then, this new system enabled to measure clearance level activity included in cemented waste. Besides, we modified the optimum structure of the detector bank, which enabled to measure precisely even metal compaction waste (the density is 34 g/cm). In this session, we introduce the process of the past research, applied examples, recent results of the research.
Haruyama, Mitsuo; Takamine, Jun; Takase, Misao; Yamaguchi, Satoshi
Nihon Hozen Gakkai Dai-1-Kai "Kensa, Hyoka, Hozen Ni Kansuru Renkei Koenkai", p.122 - 125, 2008/01
When a radioactive waste package fixed by a material such as the cement is measured by using conventional active neutron method, the problems related to quantification accuracy comes from fact that radial sensitivity distribution in the region of surface and center is different more than 100 times. In order to resolve the problem, we developed the method to detect a nuclear fission neutron induced by the neutron which slowed down in the matrix itself. By using this new method, we performed a position sensitivity difference of 10%. Recently, the inspection method to prevent the smuggling of the fissile material at the water's edge is demanded around the world. Presently, we progress the research and development to apply this new method to the inspection. In this research, we confirmed its availability through computer simulation.