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Saito, Yoshika*; Ito, Naomi*; Abe, Toshiki*; Yamamoto, Chika*; Matsumoto, Chihiro*; Zhao, T.*; Moriyama, Nobuaki*; Yoshimura, Kazuya; Sanada, Yukihisa; Tsubokura, Masaharu*
Journal of Radiological Protection, 46(1), p.013502_1 - 013502_8, 2026/03
Times Cited Count：0 Percentile：0.00(Environmental Sciences)Ito, Kei*; Matsushita, Kentaro; Ezure, Toshiki; Tanaka, Masaaki; Odaira, Naoya*; Ito, Daisuke*; Saito, Yasushi*
Nihon Kikai Gakkai 2025-Nendo Nenji Taikai Koen Rombunshu (Internet), 5 Pages, 2025/09
The estimation of entrained gas flow rate by a bathtub vortex is important in terms of a possibility to causes the performance degradation when the entrained bubbles are mixed into fluid machineries, e.g. pumps. In this study, to confirm the applicability of a model based on circulating annular flow model proposed by the authors, entrained gas flow rate is evaluated using the liquid velocity distribution around free surface dent of vortex (gas core), obtained by CFD data. As a result, it was indicated that it would be possible to evaluate the gas entrainment flow rate by setting an appropriate evaluation region.
Saito, Toshiki*; Yu, H.*; Gao, Z.*; Inoue, Koji*; Kondo, Sosuke*; Kasada, Ryuta*; Nagai, Yasuyoshi*; Oba, Yojiro*; Hiroi, Kosuke
Journal of Alloys and Compounds, 983, p.173852_1 - 173852_12, 2024/05
Times Cited Count：10 Percentile：73.01(Chemistry, Physical)Song, K.*; Ito, Kei*; Ito, Daisuke*; Odaira, Naoya*; Saito, Yasushi*; Matsushita, Kentaro; Ezure, Toshiki; Tanaka, Masaaki
Proceedings of 30th International Conference on Nuclear Engineering (ICONE30) (Internet), 10 Pages, 2023/05
Gas entrainment (GE) phenomena caused by a free surface vortex may cause the disturbance in core power of sodium-cooled fast reactor (SFR). For this reason, the entrained gas flow rate by the GE should be evaluated accurately for the practical safety design of SFRs. In this study, for the purpose of examining the applicability of CFD for the accurate evaluation of GE phenomena, a CFD is applied to the simulation of the free surface vortex and accompanied GE phenomena in a cylindrical vessel with a suction pipe, and the CFD results and the experimental data of the GE are compared. As a result, the CFD and experiments show similar two-phase flow pattern inside the suction pipe, and the shape of the gas core at the free surface is also very similar. Therefore, it is confirmed that the CFD can predict the GE phenomena triggered by a free surface vortex properly and accurately within the acceptable error range.
Ohshima, Hiroyuki; Morishita, Masaki*; Aizawa, Kosuke; Ando, Masanori; Ashida, Takashi; Chikazawa, Yoshitaka; Doda, Norihiro; Enuma, Yasuhiro; Ezure, Toshiki; Fukano, Yoshitaka; et al.
Sodium-cooled Fast Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.3, 631 Pages, 2022/07
This book is a collection of the past experience of design, construction, and operation of two reactors, the latest knowledge and technology for SFR designs, and the future prospects of SFR development in Japan. It is intended to provide the perspective and the relevant knowledge to enable readers to become more familiar with SFR technology.
Torikawa, Tomoaki*; Odaira, Naoya*; Ito, Daisuke*; Ito, Kei*; Saito, Yasushi*; Matsushita, Kentaro; Ezure, Toshiki; Tanaka, Masaaki
Konsoryu, 36(1), p.63 - 69, 2022/03
On free surface of a sodium cooled fast reactor, gas entrainment can be caused by free surface vortices, which may result in disturbance in core power. It is important to develop an evaluation model to predict accurately entrained gas flow rate. In this study, entrained gas flow rate a simple gas entrainment experiment is conducted with focusing on effect of pressure difference between upper and lower tanks. Pressure difference between upper and lower tanks are controlled by changing gas pressure in lower tank. As a result, it is confirmed that the entrained gas flow rate increases with increasing pressure difference between upper and lower tanks. By visualization of swirling annular flow in suction pipe, it is also observed that pressure drop in suction pipe increases with increase in entrained gas flow rate, which implies that entrained gas flow rate can be predicted by evaluation model based on pressure drop in swirling annular flow region.
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CuOAsano, Shun*; Ishii, Kenji*; Matsumura, Daiju; Tsuji, Takuya; Kudo, Kota*; Taniguchi, Takanori*; Saito, Shin*; Sunohara, Toshiki*; Kawamata, Takayuki*; Koike, Yoji*; et al.
Physical Review B, 104(21), p.214504_1 - 214504_7, 2021/12
Times Cited Count：2 Percentile：8.04(Materials Science, Multidisciplinary)Ito, Kei*; Ito, Daisuke*; Saito, Yasushi*; Ezure, Toshiki; Matsushita, Kentaro; Tanaka, Masaaki; Imai, Yasutomo*
Proceedings of 18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18) (USB Flash Drive), p.6632 - 6642, 2019/08
In this paper, a mechanistic model is proposed to calculate the entrained gas flow rate by a free surface vortex. The model contains the theoretical equation of transient gas core elongation and the empirical equation of critical gas core length for gas bubble detachment. Based on those two equations, the entrained gas flow rate is calculated as the portion of the gas core elongated beyond the critical gas core length per unit time. Then, the mechanistic model was applied to the calculation of the entrained gas flow rate in a simple water experiment. As a result, it is confirmed that the entrained gas flow rate grows rapidly when the liquid (water) flow rate, which determine the strength of a free surface vortex, exceeds a certain threshold value.
Cs plumes from the Fukushima Daiichi Nuclear Power Plant; Evaluation of the model intercomparison data of the Science Council of JapanKitayama, Kyo*; Morino, Yu*; Takigawa, Masayuki*; Nakajima, Teruyuki*; Hayami, Hiroshi*; Nagai, Haruyasu; Terada, Hiroaki; Saito, Kazuo*; Shimbori, Toshiki*; Kajino, Mizuo*; et al.
Journal of Geophysical Research; Atmospheres, 123(14), p.7754 - 7770, 2018/07
Times Cited Count：29 Percentile：63.71(Meteorology & Atmospheric Sciences)We compared seven atmospheric transport model results for Cs released during the Fukushima Daiichi Nuclear Power Plant accident. All the results had been submitted for a model intercomparison project of the Science Council of Japan in 2014. We assessed model performance by comparing model results with observed hourly atmospheric concentrations of Cs, focusing on nine plumes over the Tohoku and Kanto regions. The results showed that model performance for Cs concentrations was highly variable among models and plumes. We also assessed model performance for accumulated Cs deposition. Simulated areas of high deposition were consistent with the plume pathways, though the models that best simulated Cs concentrations were different from those that best simulated deposition. The ensemble mean of all models consistently reproduced Cs concentrations and deposition well, suggesting that use of a multimodel ensemble results in more effective and consistent model performance.
Koma, Yoshikazu; Ashida, Takashi; Meguro, Yoshihiro; Miyamoto, Yasuaki; Sasaki, Toshiki; Yamagishi, Isao; Kameo, Yutaka; Terada, Atsuhiko; Hiyama, Toshiaki; Koyama, Tomozo; et al.
Proceedings of International Nuclear Fuel Cycle Conference; Nuclear Energy at a Crossroads (GLOBAL 2013) (CD-ROM), p.736 - 743, 2013/09
Fukushima Daiichi Nuclear Power Station (F1NPS), TEPCO, was severely damaged with the hydrogen explosions caused by losing their cooling functions due to the earthquake and the tsunami occurred on March 11, 2011. Radioactive wastes generated from the current FINPS and future their decommission and demolition are greater huge amount than those from general reactors and nuclear fuel facilities. Toward accomplishing safe and reasonable management of the wastes, great effort of R&Ds has been strongly required and performed in bringing together the knowledge and experience of all of Japan. This report outlines the current status of the R&Ds performed in JAEA.
Kondo, Hiroaki*; Yamada, Tetsuji*; Chino, Masamichi; Iwasaki, Toshiki*; Katata, Genki; Maki, Takashi*; Saito, Kazuo*; Terada, Hiroaki; Tsuruta, Haruo*
Tenki, 60(9), p.723 - 729, 2013/09
no abstracts in English
Saito, Kimiaki; Saito, Hidetoshi*; Kunieda, Etsuo*; Narita, Yuichiro*; Myojoyama, Atsushi*; Fujisaki, Tatsuya*; Kawase, Takatsugu*; Kaneko, Katsutaro*; Ozaki, Masahiro*; Deloar, H. M.*; et al.
Joho Shori, 48(10), p.1081 - 1088, 2007/10
no abstracts in English
Orukawa, Go; Kojima, Wataru; Shirato, Nobuaki*; Saito, Toshiki*
Konkurito Kogaku Nenji Rombunshu (DVD-ROM), 28(1), p.1637 - 1642, 2006/00
no abstracts in English
Fukuda, Mitsuhiro; Okumura, Susumu; Kurashima, Satoshi; Miyawaki, Nobumasa; Ishii, Yasuyuki; Saito, Yuichi; Mizuhashi, Kiyoshi; Agematsu, Takashi; Chiba, Atsuya; Sakai, Takuro; et al.
Proceedings of 1st Annual Meeting of Particle Accelerator Society of Japan and 29th Linear Accelerator Meeting in Japan, p.643 - 645, 2004/08
A superconducting AVF cyclotron with a bending limit of 900 MeV and a focusing limit of 300 MeV is being designed to meet the requirements for the research in materials science and biotechnology at TIARA facility of JAERI. The spiral-sector shape of the cyclotron magnet has been optimized for acceleration of a 300 MeV proton to produce sufficient focusing forces in an extraction region. An energy range of the superconducting AVF cyclotron overlaps with that of the present K110 JAERI AVF cyclotron. Characteristics of a resonator for the superconducting AVF cyclotron have been investigated using the MAFIA code. An acceleration voltage in a frequency range of 24 to 64 MHz can be produced by the resonator with a 
/2 excitation mode.
Fukuda, Mitsuhiro; Okumura, Susumu; Ishii, Yasuyuki; Saito, Yuichi; Miyawaki, Nobumasa; Mizuhashi, Kiyoshi; Agematsu, Takashi; Kurashima, Satoshi; Chiba, Atsuya; Sakai, Takuro; et al.
Dai-14-Kai Kasokuki Kagaku Kenkyu Happyokai Hokokushu, p.302 - 304, 2003/00
no abstracts in English
Zhidkov, A. G.; Sasaki, Akira; Utsumi, Takayuki*; Fukumoto, Ichiro; Tajima, Toshiki; Saito, Fumikazu*; Hironaka, Yoichiro*; Nakamura, Kazutaka*; Kondo, Kenichi*; Yoshida, Masataka*
Physical Review E, 62(5), p.7232 - 7240, 2000/11
Times Cited Count：52 Percentile：85.28(Physics, Fluids & Plasmas)no abstracts in English
Watanabe, Katsutoshi; Shindo, Masami; Nakajima, Hajime; Koikegami, Hajime*; Higuchi, Makoto*; Nakanishi, Tsuneo*; Sahira, Kensho*; Marushichi, Koki*; Takeiri, Toshiki*; Saito, Teiichiro*; et al.
JAERI-Research 97-009, 62 Pages, 1997/02
JAERI-Research-97-009.pdf:4.82MB
no abstracts in English
Watanabe, Katsutoshi; Nakajima, Hajime; Saito, Teiichiro*; Takatsu, Tamao*; Koikegami, Hajime*; Higuchi, Makoto*; Nakanishi, Tsuneo*; Sahira, Kensho*; Marushichi, Koki*; Takeiri, Toshiki*
JAERI-Research 94-046, 50 Pages, 1994/12
JAERI-Research-94-046.pdf:2.23MB
no abstracts in English
Watanabe, Katsutoshi; Nakajima, Hajime; Sahira, Kensho*; Marushichi, Koki*; Takeiri, Toshiki*; Saito, Teiichiro*; Takatsu, Tamao*; Nakanishi, Tsuneo*; Koikegami, Hajime*; Higuchi, Makoto*
Proc. of the 2nd JAERI Symp. on HTGR Technologies; Oct. 21
23,1992,Oarai,Japan (JAERI-M 92-215), p.560 - 574, 1993/01
no abstracts in English
Watanabe, Katsutoshi; Nakajima, Hajime; Sahira, Kensho*; Marushichi, Koki*; Takeiri, Toshiki*; Saito, Teiichiro*; Takatsu, Tamao*; Nakanishi, Tsuneo*; Koikegami, Hajime*; Higuchi, Makoto*
Tainetsu Kinzoku Zairyo Dai-123-Iinkai Kenkyu Hokoku, 33(2), p.227 - 242, 1992/00
no abstracts in English
