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Kataoka, Ryuho*; Nishiyama, Takanori*; Tanaka, Yoshimasa*; Kadokura, Akira*; Uchida, Herbert Akihito*; Ebihara, Yusuke*; Ejiri, Mitsumu*; Tomikawa, Yoshihiro*; Tsutsumi, Masaki*; Sato, Kaoru*; et al.
Earth, Planets and Space (Internet), 71(1), p.9_1 - 9_10, 2019/12
Times Cited Count:8 Percentile:40.25(Geosciences, Multidisciplinary)Transient ionization of the mesosphere was detected at around 65 km altitude during the isolated auroral expansion occurred at 2221-2226 UT on June 30, 2017. A general-purpose Monte Carlo particle transport code PHITS suggested that significant ionization is possible in the middle atmosphere due to auroral X-rays from the auroral electrons of 10 keV.
Someya, Satoshi*; Uchida, Mitsunori*; Uchibori, Akihiro; Ohshima, Hiroyuki; Li, Y.*; Okamoto, Koji*
Nihon Kikai Gakkai Rombunshu, B, 75(759), p.2173 - 2181, 2009/11
When the pressurized water or water vapor leaks from a failed heat transfer tube in a steam generator of sodium cooled fast reactors, the high-velocity and high-temperature jet with sodium-water chemical reaction may cause wastage of the adjacent tubes. The evaluation of the wastage rate requires numerical analysis of the reaction jet. To construct a numerical method for the reaction jet, experiment on the underexpanded gas jet into the liquid pool need to be done. In this study visualization and measurement for the underexpanded nitrogen gas jet injected into the water was carried out. The horizontal penetration length of the gas jet and the expansion angle were obtained from the averaged images of a high-speed camera. The experimental results showed that the penetration length and the expansion angle increased approximately linearly with increasing stagnation pressure. The entrainment velocity and the velocity of the entrained water droplets were obtained by PIV.
Uchida, Mitsunori*; Someya, Satoshi*; Okamoto, Koji*; Ohshima, Hiroyuki
Proceedings of 13th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-13) (CD-ROM), 13 Pages, 2009/09
When a heat exchanger in fast breeder reactor cracks, a sodium-water reaction occurs. Highly pressurized water or steam escapes into the surrounding liquid sodium. The release of steam into the liquid sodium media is a two-phase flow with an underexpansion. Several studies have examined only the underexpansion of the gas-gas phase. However, there are few reports on the underexpansion of the gas-liquid phase. In this study quantitative measurement was carried out for the purpose of revealing the flow with the underexpanded gas jet injected into water. The gas jet distance and the expansion angle were then obtained from the averaged images of a high-speed camera. The gas jet distance and the expansion angle increased approximately linearly with increasing pressure. The entrainment velocity and the velocity of entrained water droplets into the gas jet were obtained by PIV.
Uchida, Mitsunori*; Someya, Satoshi*; Okamoto, Koji*; Ohshima, Hiroyuki
Proceedings of 6th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-6) (USB Flash Drive), 6 Pages, 2008/11
When a heat exchanger in a fast breeder reactor cracks, a sodium-water reaction occurs. When a tube cracks, highly pressurized water or steam escapes into the surrounding liquid sodium. The release of steam into the liquid sodium media is a two-phase flow with an underexpansion. There have been few reports on the underexpansion of the gas-liquid phase. In this paper, qualitative measurement of the two-phase flow was carried out for the purpose of revealing the flow with the underexpanded gas jet injected into water. The gas jet range and the gas jet width were then obtained from averaged images of a high-speed camera. PIV was also carried out by observing scattering light from the gas bubbles. The gas jet range and the gas jet width increased approximately linearly with increasing pressure. The results of PIV showed that the bubble velocity increased increasing pressure.
Nakahira, Masataka; Shibanuma, Kiyoshi; Kajiura, Soji*; Shibui, Masanao*; Koizumi, Koichi; Takeda, Nobukazu; Kakudate, Satoshi; Taguchi, Ko*; Oka, Kiyoshi; Obara, Kenjiro; et al.
JAERI-Tech 2002-029, 27 Pages, 2002/03
The ITER vacuum vessel (VV) R&D has progressed with the international collaborative efforts by the Japan, Russia and US Parties during the Engineering Design Activities (EDA). Fabrication and testing of a full-scale VV sector model and a port extension have yielded critical information on the fabrication and assembly technologies of the vacuum vessel, magnitude of welding distortions, dimensional accuracy and achievable tolerances during sector fabrication and field assembly. In particular, the dimensional tolerances of 3 mm for VV sector fabrication and 10 mm for VV sector field assembly have been achieved and satisfied the requirements of 5 mm and 20 mm, respectively. Also, the basic feasibility of the remote welding robot has been demonstrated. This report presents detailed fabrication and assembly technologies such as welding technology applicable to the thick wall without large distortion, field joint welding technology between sectors and remote welding technology through the VV R&D project.
Uchida, Mitsunori*; Someya, Satoshi*; Okamoto, Koji*; Ohshima, Hiroyuki
no journal, ,
When a heat exchanger in a fast breeder reactor cracks, a sodium-water reaction occurs. Highly pressurized water or steam escapes into the surrounding liquid sodium. The release of steam into the liquid sodium media is a two-phase flow with an under expansion. Several studies have examined the under expansion of the gas-gas phase. However, there are few reports on the underexpansion of the gas-liquid phase. In this study quantitative measurement was carried out for the purpose of revealing the flow with the underexpanded gas jet injected into water. The gas jet distance and the expansion angle were then obtained from averaged images of a high-speed camera. The entrainment velocity and the velocity of the entrained water droplets were also obtained by PIV.