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Journal Articles

Visualization of gas-liquid interfacial behavior in a narrow channel using high-speed neutron imaging

Ito, Daisuke*; Odaira, Naoya*; Ito, Kei*; Saito, Yasushi*; Kurita, Keisuke; Iikura, Hiroshi

Konsoryu, 37(1), p.73 - 78, 2023/03

Gas-liquid two-phase flow is a very complicated flow phenomenon that involves the interaction between gas and liquid phases. Recently, an accurate simulation technique of two-phase flow has been developed. However, the validation of the simulated results is insufficient due to less experimental data. It is especially difficult to measure interfacial behavior with significant spatiotemporal fluctuation. To understand such phenomena, measurement methods with high spatial and temporal resolutions are required. Neutron imaging is a powerful tool for two-phase flow visualization. In this study, two-phase flow in the narrow rectangular channel was visualized by high-speed neutron imaging.

Journal Articles

Development of particle collection technique by using bubble breakup phenomenon in venturi tube

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.

Journal Articles

Measurement of void fraction distribution in a sphere-packed bed using X-ray imaging

Yamamoto, Seishiro*; Odaira, Naoya*; Ito, Daisuke*; Ito, Kei*; Saito, Yasushi*; Imaizumi, Yuya; Matsuba, Kenichi; Kamiyama, Kenji

Konsoryu, 37(1), p.79 - 85, 2023/03

Journal Articles

Development of particle removal technique by using bubble breakup phenomenon in converging-diverging nozzle

Uesawa, Shinichiro; Yoshida, Hiroyuki

Konsoryu Shimpojiumu 2022 Koen Rombunshu (Internet), 2 Pages, 2022/08

no abstracts in English

Journal Articles

Evaluation of gas entrainment flow rate by free surface vortex

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.

Journal Articles

Local gas-liquid two-phase flow characteristics in rod bundle geometry

Xiao, Y.*; Shen, X.*; Miwa, Shuichiro*; Sun, Haomin; Hibiki, Takashi*

Konsoryu Shimpojiumu 2018 Koen Rombunshu (Internet), 2 Pages, 2018/08

In order to develop constitutive equations of two-fluid model in rod bundle flow channels, experiments of adiabatic air-water upward two-phase flow in 6$$times$$6 rod bundle flow channel were performed. Local flow parameters such as void fraction, interfacial area concentration (IAC) and so on were measured by a double-sensor optical probe. The area-averaged void fraction and IAC data were compared with the predictions from a drift-flux model and an IAC correlation.

Journal Articles

Development of simultaneous evaluation method of bubble behavior and electric field distribution around WMS by using TPFIT and EMSolution

Uesawa, Shinichiro; Suzuki, Takayuki*; Yoshida, Hiroyuki

Konsoryu Shimpojiumu 2018 Koen Rombunshu (Internet), 2 Pages, 2018/08

no abstracts in English

Journal Articles

Observation of aerosol behavior near droplet interface

Uesawa, Shinichiro; Yoshida, Hiroyuki

Konsoryu, 32(1), p.140 - 149, 2018/03

no abstracts in English

Journal Articles

Observation of aerosol behavior near droplet interface

Uesawa, Shinichiro; Yoshida, Hiroyuki

Konsoryu Shimpojiumu 2017 Koen Rombunshu (USB Flash Drive), 2 Pages, 2017/08

no abstracts in English

Journal Articles

Study on forced-convective boiling heat transfer of seawater with sea salt deposition

Uesawa, Shinichiro; Koizumi, Yasuo; Shibata, Mitsuhiko; Nagatake, Taku; Yoshida, Hiroyuki

Konsoryu, 31(2), p.162 - 170, 2017/06

no abstracts in English

Journal Articles

Visualization study on two-phase flow behavior at spray cooling for spent fuel pool

Nagatake, Taku; Liu, W.; Uesawa, Shinichiro; Koizumi, Yasuo; Shibata, Mitsuhiko; Yoshida, Hiroyuki; Nemoto, Yoshiyuki; Kaji, Yoshiyuki

Konsoryu Shimpojiumu 2016 Koen Rombunshu (USB Flash Drive), 2 Pages, 2016/08

no abstracts in English

Journal Articles

Experimental measurement of vortex cavitation around a suction pipe inlet

Ezure, Toshiki; Ito, Kei; Kameyama, Yuri*; Kurihara, Akikazu; Kunugi, Tomoaki*

Konsoryu, 30(2), p.189 - 196, 2016/06

Journal Articles

Experiments of coolant accumulation in SG U tube and analytical model development

Yamaji, Tatsuya*; Koizumi, Yasuo; Yamazaki, Kohei*; Otake, Hiroyasu*; Hasegawa, Koji*; Onuki, Akira*; Kanamori, Daisuke*

Konsoryu Shimpojiumu 2015 Koen Rombunshu (USB Flash Drive), 2 Pages, 2015/08

Experiments of condensing counter-current two-phase flow in a vertical pipe were performed. This study was intended to examine water accumulation in the up-flow side of steam generator U-tubes of a PWR during the reflux cooling stage of a small break LOCA. It has been apprehended that the water accumulation may result in temporary core liquid level depression. The inner diameter and the length of a test flow channel used in the experiments were 18 mm and 4 m, respectively. The experiments were performed by using steam and water at 0.1 MPa. Two kinds of experiments were conducted; visualization experiments by using a transparent test section and quantitative water accumulation evaluation experiments by using a brass test section. Even if water on the inner surface of the test pipe could not flow downward at the lower portion of the test pipe, a part of water became to flow downward at the upper portion of the test pipe since steam velocity decreased because of condensation. Thus, two-phase mixture level was formed in the upper portion of the test pipe, which resulted in the water accumulation in the pipe. The model to predict the water accumulation was proposed. It predicted the water accumulation reasonably well.

Journal Articles

JAEA's environmental remediation activities for Fukushima

Umezawa, Katsuhiro; Nakayama, Shinichi

Konsoryu, 26(4), p.418 - 425, 2012/12

JAEA has been conducting diversified activities on the environmental remediation for Fukushima after the Great East Japan Earthquake, including radiation monitoring, decontamination demonstration, public communications, and related R&D. The decontamination pilot project was carried out in the off-limit and scheduled evacuation zones, where existing and/or improved clean-up techniques were tested their applicability and efficiency, waste storage was established, and how to secure workers' safety for radiation was investigated. Related R&D has also been continued, such as computer simulation for decontamination planning, and aircraft radiation monitoring.

Journal Articles

Multiphase technology in nuclear engineering area; Development of two-phase flow analysis codes for reactor design

Akimoto, Hajime

Konsoryu, 26(3), p.266 - 272, 2012/09

Research and development activities for two-phase analysis codes for nuclear reactor design and safety analyses have been reviewed focusing in recent twenty five years. For reactor safety evaluation, large-scale tests were performed to confirm effectiveness of ECCS in 1980's and 1990's. These test results were succeeded to so-called best-estimate codes such as RELAP5, TRAC codes. Severe accident researches were performed in 1980's and 1990's and accident management methods were studied. Detailed simulation methods such as subchannel analysis, multi-dimensional analyses have been developed based on test results and computational technology enhancement in 1990's and 2000's. Future scope is summarized briefly.

Journal Articles

High-precision calculation of interface normal on non-orthogonal mesh

Ito, Kei; Kunugi, Tomoaki*; Ohshima, Hiroyuki

Konsoryu, 26(1), p.52 - 59, 2012/03

For the purpose of direct simulations of gas entrainment phenomenon in fast reactors, the authors are developing a high-precision simulation algorithm for gas-liquid two-phase flows on non-orthogonal meshes. In this paper, the calculation method for an interface normal is improved by developing a height function algorithm on non-orthogonal meshes. As a result of basic verification, the height function algorithm succeeds in reproducing rectilinear interfaces on a non-orthogonal triangular mesh. In addition, an interfacial curvature is calculated accurately based on the interface normal calculated by the height function algorithm.

Journal Articles

Numerical analysis of windowless target in accelerator driven system by use of TPFIT

Yoshida, Hiroyuki; Suzuki, Takayuki*; Takase, Kazuyuki

Nihon Konsoryu Gakkai Nenkai Koenkai 2010 Koen Rombunshu, p.344 - 345, 2010/07

no abstracts in English

Journal Articles

Evaluation of influence of an earthquake acceleration upon boiling two phase flow behavior

Misawa, Takeharu; Yoshida, Hiroyuki; Takase, Kazuyuki

Nihon Konsoryu Gakkai Nenkai Koenkai 2010 Koen Rombunshu, p.92 - 93, 2010/07

no abstracts in English

Journal Articles

Development of prediction method of turbulent heat transfer for thermal-hydraulic design of supercritical water reactor

Nakatsuka, Toru; Misawa, Takeharu; Yoshida, Hiroyuki; Takase, Kazuyuki

Nihon Konsoryu Gakkai Nenkai Koenkai 2010 Koen Rombunshu, p.348 - 349, 2010/07

In the thermal hydraulic design of supercritical water-cooled reactor, it is required to establish a thermal hydraulic design method which can precisely predict heat transfer deterioration of supercritical water as the core coolant. Assessments of applicability of turbulence models used in design methods have not been sufficiently performed, since the mechanism of heat transfer deterioration has not been clearly figured out yet. Japan Atomic Energy Agency has started developing prediction method of heat transfer deterioration with large eddy simulation to improve the thermal hydraulic design accuracy. In the present study, simulation results of heat transfer test with Freon are reported.

Journal Articles

Cavitation in high-power pulsed spallation neutron sources

Futakawa, Masatoshi; Tanaka, Nobuatsu*

Konsoryu, 24(2), p.138 - 145, 2010/06

High-power pulsed spallation neutron sources are being developed in the world. A mercury target is installed at MLF (Materials and Life science experimental Facility) in J-PARC (Japan Proton Accelerator Research Complex), which will promote innovative science. At the moment the proton beams bombard the mercury target, pressure waves will be generated in mercury by thermally shocked heat deposition. Cavitation will be induced through the pressure wave propagation in mercury and eroded the vessel inner surface contacting with mercury, i.e. pitting damage. The eroded vessel wall is damaged by cyclic fatigue because pulsed proton beams strike the target repeatedly. In the paper, the effects of pitting damage, cyclic fatigue damage and mercury environment on the lifetime of the mercury target, and mitigation techniques for pressure waves and cavitation damage are described.

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