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Uesawa, Shinichiro; Shibata, Mitsuhiko; Yoshida, Hiroyuki
Konsoryu, 37(1), p.55 - 64, 2023/03
In decommissioning Fukushima Daiichi Nuclear Power Station, the issue is confinement of radioactive aerosols in the primary containment vessel. Although a High Efficiency Particulate Air (HEPA) filter is used to collect the aerosol particles, pretreatment equipment such as a scrubber may be applied to reduce the load of HEPA filters. In the scrubber, the aerosol particles are removed by moving from gas to liquid through gas-liquid interface. Since the collection efficiency (CE) depends on gas-liquid interfacial area, fine bubbles are necessary to obtain high collection efficiency. JAEA developed a new particle removal technique by using bubble breakup phenomenon in a Venturi tube. To confirm usefulness of the technique, we performed the CE measurements and observed gas-liquid two-phase flow in the Venturi tube. In comparison with a straight pipe type, the Venturi type can have removed particles more 1,000 than it. The CE is almost the same as a HEPA filter. In addition, the Venturi type has the enough CE as the pretreatment equipment for various materials of particles such as Kanto loam, SUS and oil. Besides, we clarified that the CE of the Venturi type depended on the gas and liquid flow rates. The CE increases with the increase of the liquid flow rate but decreases with the increase of the gas flow rate. This is because the CE is affected by the bubble breakup phenomenon in the Venturi tube. In the experiment, we confirmed that cavitation number which is the parameter of the bubble breakup was related to the CE of the Venturi type.
Kogawa, Hiroyuki; Futakawa, Masatoshi; Haga, Katsuhiro; Tsuzuki, Takayuki*; Murai, Tetsuro*
JAEA-Technology 2022-023, 128 Pages, 2022/11
JAEA-Technology-2022-023.pdf:9.0MB
In a mercury target of the J-PARC (Japan Proton Accelerator Research Complex), pulsed proton beams repeatedly bombard the flowing mercury which is confined in a stainless-steel vessel (target vessel). Cavitation damage caused by the propagation of the pressure waves is a factor of the life of the target vessel. As a measure to reduce damages, we developed a bubbler to inject the gas microbubbles into the flowing mercury, which can reduce the pressure waves. To operate the mercury target vessel stably with the 1 MW high-intensity proton beams, further reduction of the damage is required. The bubbler setting position should be closer to the beam window to increase the bubble population, which could enhance the reduction effect on the pressure waves and damage. However, the space at the beam window of the target vessel is restricted. The bubbler design and setting position as well as the vane design for the mercury flowing pattern are optimized by means of a machine learning technique to get more suitable bubble distribution, increasing in bubble population and optimizing bubble size nearby the beam window of the target vessel. The results of CFD analyses performed with 1000 cases were used for machine learning. Since the flow rate of mercury affects the temperature of the target vessel, this was used for the constraint condition. As a result, we found a design of mercury target vessel that can increase the bubble population by ca. 20% higher than the current design.
Uesawa, Shinichiro; Yoshida, Hiroyuki
Konsoryu Shimpojiumu 2022 Koen Rombunshu (Internet), 2 Pages, 2022/08
no abstracts in English
Takada, Hiroshi
JAEA-Conf 2017-001, p.51 - 56, 2018/01
A pulsed spallation neutron source of Japan Proton Accelerator Research Complex (J-PARC) is aimed at promoting a variety of cutting-edge materials researches at state-of-the-art neutron instruments with neutrons generated by a 3-GeV proton beam with a power of 1-MW at a repetition rate of 25 Hz. In 2015, for the first time it received 1-MW equivalent proton beam pulse, and the beam power for user program was ramped up to 500 kW. The moderator system of the neutron source was optimized to use (1) 100% para-hydrogen for increasing pulse peak intensity with decreasing pulse tail, (2) cylindrical shape with 14 cm diam. 
12 cm long for providing high intensity neutrons to wide neutron extraction angles of 50.8 degrees, (3) neutron absorber made from Ag-In-Cd alloy to make pulse widths narrower and pulse tails lower. As a result, it gives highest intensity pulsed neutrons per incident proton in the world. Towards the goal to achieve the target operation at 1-MW for 5000 h in a year, efforts to mitigate cavitation damages at the target vessel front with injecting gas micro-bubbles into the mercury target are under way. Also, improvement of structural target vessel design is an urgent issue since there was failure twice at the water shroud of the mercury target due to the thermal stress during operating periods at 500 kW in 2015.
Sakka, Taku*; Jiao, L.; Uesawa, Shinichiro; Yoshida, Hiroyuki; Takase, Kazuyuki
Nihon Kikai Gakkai 2015-Nendo Nenji Taikai Koen Rombunshu (DVD-ROM), 5 Pages, 2015/09
no abstracts in English
Takase, Kazuyuki; Ose, Yasuo*; Yoshida, Hiroyuki; Akimoto, Hajime; Satake, Shinichi*
Proceedings of International Conference on Jets, Wakes and Separated Flows (ICJWSF 2005), p.137 - 144, 2005/11
no abstracts in English
Ida, Masato
Nihon Ryutai Rikigakkai Nenkai 2005 Koen Rombunshu (CD-ROM), 6 Pages, 2005/09
The resonance frequencies and oscillation phases of three acoustically coupled bubbles in a fluid are examined to show that avoided crossings can appear in a few-bubble system. Using a simple coupled oscillator model, we show that if at least three bubbles exist, it is possible for their resonance frequencies as functions of the separation distances between the bubbles to experience an avoided crossing. Furthermore, by focusing our attention on the oscillation phases and the transition frequencies [Ida, Phys. Lett. A 297, 210 (2002); J. Phys. Soc. Jpn. 71, 1214 (2002)] of the coupled bubbles, we show that a distinct state exchange takes place between the bubbles at a point in the avoided crossing region, where a resonance frequency of the triple-bubble system crosses with a transition frequency not corresponding to the resonance frequencies.
Ida, Masato
Physical Review E, 72(3), p.036306_1 - 036306_7, 2005/09
Times Cited Count：14 Percentile：54.05(Physics, Fluids & Plasmas)The resonance frequencies and oscillation phases of three acoustically coupled bubbles are examined to show that avoided crossings can appear in a multibubble system. Via a simple coupled oscillator model, we show that if at least three bubbles exist, it is possible for their resonance frequencies to experience an avoided crossing. Furthermore, by focusing our attention on the oscillation phases and based on analysis of the transition frequencies [Ida, Phys. Lett. A 297, 210 (2002); Ida, J. Phys. Soc. Jpn. 71, 1214 (2002)] of the coupled bubbles, we show that a distinct state exchange takes place between the bubbles at a point in the avoided crossing region, where a resonance frequency of the triple-bubble system crosses with a transition frequency.
Ida, Masato
Physics of Fluids, 17(9), p.097107_1 - 097107_13, 2005/09
Times Cited Count：16 Percentile：52.83(Mechanics)The transition frequencies of multibubble systems in a sound field are reexamined theoretically to confirm their existence and further clarify their physical properties. Via a forced coupled oscillator model, the following results are obtained: (1) further details of the characteristics of the transition frequencies, (2) the theoretical determination of the threshold distances for the appearance of the sub-transition frequencies, (3) a simple understanding of the sign reversal of the interaction force, and (4) the clarification of several similarities and differences among the natural, resonance, and transition frequencies in double-bubble cases. The present effort enforces our claim that transition frequencies causing no resonance response exist in multibubble systems and thoroughly clarifies the physical effects of the transition frequencies and their roles in the sign reversal of the interaction force.
Takase, Kazuyuki; Ose, Yasuo*; Yoshida, Hiroyuki; Akimoto, Hajime; Aoki, Takayuki*
Dai-24-Kai Nihon Shimyureshon Gakkai Taikai Happyo Rombunshu, p.161 - 164, 2005/07
no abstracts in English
Takase, Kazuyuki; Yoshida, Hiroyuki; Ose, Yasuo*
Hai Pafomansu Komputingu To Keisan Kagaku Shimpojium (HPCS 2005) Rombunshu, P. 16, 2005/01
no abstracts in English
Ose, Yasuo*; Takase, Kazuyuki; Yoshida, Hiroyuki; Kano, Takuma; Akimoto, Hajime
Dai-18-Kai Suchi Ryutai Rikigaku Shimpojiumu Koen Yoshishu (CD-ROM), 6 Pages, 2004/12
no abstracts in English
Yoshida, Hiroyuki; Nagayoshi, Takuji*; Tamai, Hidesada; Takase, Kazuyuki; Akimoto, Hajime
Proceedings of 4th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-4), p.264 - 269, 2004/12
no abstracts in English
Ose, Yasuo*; Takase, Kazuyuki; Yoshida, Hiroyuki
Proceedings of 1st International Forum on Heat Transfer (IFHT 2004), p.199 - 200, 2004/11
no abstracts in English
Ida, Masato
Proceedings of 6th World Congress on Computational Mechanics in conjunction with 2nd Asian-Pacific Congress on Computational Mechanics (CD-ROM), p.1 - 11, 2004/09
The existence of the "transition frequencies" of two acoustically coupled gas bubbles has been verified by direct numerical simulation. The theory described by Ida [Phys. Lett. A 297 (2002) 210] predicted that a bubble in the double-bubble system has three transition frequencies, some of which makes the phase difference between the bubble's volume oscillation and an external sound 
without accompanying resonance response of the bubble. In a more recent paper [Ida, Phys. Rev. E 67 (2003) 056617], it was suggested theoretically that one of the transition frequencies may cause the sign reversal of the secondary Bjerknes force acting between pulsating bubbles. In the present study, we employ a direct numerical simulation technique that uses the compressible Navier-Stokes equations with a surface-tension term as the governing equations to investigate the transition frequencies of two coupled bubbles. The numerical results clearly exhibit the existence of the theoretically predicted characteristic frequency.
Tamai, Hidesada; Tomiyama, Akio*
Nihon Kikai Gakkai Rombunshu, B, 70(692), p.50 - 57, 2004/04
no abstracts in English
Tamai, Hidesada; Tomiyama, Akio*
Nihon Kikai Gakkai Rombunshu, B, 70(692), p.58 - 65, 2004/04
no abstracts in English
Takase, Kazuyuki; Yoshida, Hiroyuki; Ose, Yasuo*; Tamai, Hidesada; Akimoto, Hajime
Transactions of the American Nuclear Society, 89, p.88 - 89, 2003/11
no abstracts in English
Watanabe, Tadashi; Ebihara, Kenichi
JSME International Journal, Series B, 45(3), p.600 - 606, 2002/08
no abstracts in English
Sakamoto, Yukio
KEK Proceedings 2001-14, p.236 - 242, 2001/06
no abstracts in English
