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Kurita, Keisuke; Iikura, Hiroshi; Tsuchikawa, Yusuke; Kai, Tetsuya; Shinohara, Takenao; Odaira, Naoya*; Ito, Daisuke*; Saito, Yasushi*; Matsubayashi, Masahito
Journal of Physics; Conference Series, 2605, p.012005_1 - 012005_6, 2023/10
The Japan Research Ractor-3 (JRR-3) is operation resumed on February 26, 2021, and the shared use was also restarted in July, 2021. With the resumption of JRR-3 operation, two imaging facilities called TNRF and CNRF have also resumed their utilization. In this presentation, we report the details of these two neutron facilities.
Saito, Yasushi*; Ito, Daisuke*; Odaira, Naoya*; Kurita, Keisuke; Iikura, Hiroshi
Journal of Physics; Conference Series, 2605, p.012028_1 - 012028_6, 2023/10
To observe flow velocity distributions by Neutron Imaging, suitable tracer is necessary. The requirements are its density, its visibility, and its wettability (if applied to liquid metal). Gold cadmium tracers have been developed for the Pb-Bi two-phase flow, however, the visibility have not been verified depending on the particle size and the measurement system. As the candidates of tracer particles, Ag, Cd, Au-Cd, and Ag-Cd have been tested by varying its compositions and its diameters. Results show enough visibility if the particles size is larger than 1mm. In addition, Cd tracer particles were applied to the fluidized bed, where the bed materials are metallic particle made of stainless steel, with 1mm diameter. The diameter of Cd trace is about 1.5 mm. From the neutron imaging, the visibility of the tracers is enough to measure the velocity distributions in the fluidized bed.
Ito, Daisuke*; Odaira, Naoya*; Ito, Kei*; Saito, Yasushi*; Kurita, Keisuke; Iikura, Hiroshi
Journal of Physics; Conference Series, 2605, p.012024_1 - 012024_6, 2023/10
Gas-liquid two-phase flow appears in many heat-exchanging devices. To understand the phenomena in such devices, the two-phase flow dynamics should be clarified. In this study, high-speed neutron imaging is applied to the measurements of two-phase flow dynamics, and the accuracy of the void fraction measurement is investigated.
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.
Yamamoto, Seishiro*; Odaira, Naoya*; Ito, Daisuke*; Ito, Kei*; Saito, Yasushi*; Imaizumi, Yuya; Matsuba, Kenichi; Kamiyama, Kenji
Konsoryu, 37(1), p.79 - 85, 2023/03
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.
Ito, Daisuke*; Sato, Hirotaka*; Odaira, Naoya*; Saito, Yasushi*; Parker, J. D.*; Shinohara, Takenao; Kai, Tetsuya; Oikawa, Kenichi
Journal of Nuclear Materials, 569, p.153921_1 - 153921_6, 2022/10
Times Cited Count：6 Percentile：51.78(Materials Science, Multidisciplinary)Yamamoto, Seishiro*; Odaira, Naoya*; Ito, Daisuke*; Ito, Kei*; Saito, Yasushi*; Imaizumi, Yuya; Matsuba, Kenichi; Kamiyama, Kenji
Proceedings of 12th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS12) (Internet), 4 Pages, 2022/10
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.
Odaira, Naoya*; Yamamoto, Seishiro*; Ito, Daisuke*; Ito, Kei*; Saito, Yasushi*; Imaizumi, Yuya; Matsuba, Kenichi; Kamiyama, Kenji
no journal, ,
no abstracts in English
Ito, Daisuke*; Odaira, Naoya*; Ito, Kei*; Saito, Yasushi*; Imaizumi, Yuya; Matsuba, Kenichi; Kamiyama, Kenji
no journal, ,
no abstracts in English
Ito, Kei*; Ito, Daisuke*; Odaira, Naoya*; Saito, Yasushi*; Song, K.*; Ezure, Toshiki; Matsushita, Kentaro; Tanaka, Masaaki
no journal, ,
The entrained gas flow rate by a bathtub vortex must be evaluated to achieve stable operation of a sodium-cooled fast reactor. In this study, a simple vortex-type gas entrainment experiment is conducted to evaluated the entrained gas flow rate under various conditions of free surface level, downstream pressure and suction pipe diameter. As a result, it is clarified that the entrained gas flow rate increases with the decrease in the downstream pressure. Based on the experimental result, we model the annular two-phase flow in the suction pipe and propose a new evaluation model of the entrained gas flow rate in which the influence of the downstream pressure.
Mizuno, Tomohiro*; Odaira, Naoya*; Ito, Daisuke*; Ito, Kei*; Saito, Yasushi*; Imaizumi, Yuya; Matsuba, Kenichi; Kamiyama, Kenji
no journal, ,
no abstracts in English
Odaira, Naoya*; Ito, Daisuke*; Ito, Kei*; Saito, Yasushi*; Imaizumi, Yuya; Matsuba, Kenichi
no journal, ,
Ito, Kei*; Odaira, Naoya*; Ito, Daisuke*; Saito, Yasushi*; Matsushita, Kentaro; Ezure, Toshiki; Tanaka, Masaaki
no journal, ,
Various studies are conducted to predict the onset condition of gas entrainment by a free surface vortex in sodium-cooled fast reactors. However, there are few studies on the estimation of entrained gas flow rate. The authors have proposed a candidate evaluation model of gas flow rate based on circulating annular flow model. In this study, to confirm the applicability of the model to actual reactors, 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, the evaluated entrained gas flow rate shows smaller value to the measurement data, which implying the interfacial friction coefficient employed in the circulating annular is optimized for flow in suction pipe and not suitable for flow around a gas core. Then, the parameter survey on the interfacial friction coefficient is performed to find an appropriate value for a realistic evaluation of entrained gas flow rate in actual reactors.
Kurita, Keisuke; Saito, Yasushi*; Ito, Daisuke*; Odaira, Naoya*; Iikura, Hiroshi
no journal, ,
Experiments have been performed to estimate the rising velocity of gas bubbles or water droplets in a liquid-metal pool. Dynamic behaviour of two-phase bubble evaporating in a molten alloy was clearly observed by using high-frame rate neutron imaging at 500 fps. Measurements of drag coefficient have been made for a single nitrogen gas bubble and for a water droplet including two-phase bubble evaporating in the liquid metal. The relationship between the rising velocity of a single bubble/droplet in the molten Newton's alloy was clarified in detail taking the bubble/droplet shape.
Fujitsu, Akito*; Odaira, Naoya*; Ito, Daisuke*; Ito, Kei*; Saito, Yasushi*; Imaizumi, Yuya; Matsuba, Kenichi; Kamiyama, Kenji
no journal, ,
no abstracts in English
Kurita, Keisuke; Iikura, Hiroshi; Harayama, Isao; Tsuchikawa, Yusuke; Kai, Tetsuya; Shinohara, Takenao; Odaira, Naoya*; Ito, Daisuke*; Saito, Yasushi*; Matsubayashi, Masahito
no journal, ,
Two large neutron experimental facilities are located at the Nuclear Science Research institute site. One is the Japan Proton Accelerator Research Complex (J-PARC). The other is the Japan Research Reactor-3 (JRR-3). Each of them has neutron imaging facilities. In this presentation, we will introduce the performances, updated devices, utilization results and imaging examples of neutron radiography facilities at the JRR-3.
Saito, Yasushi*; Odaira, Naoya*; Ito, Daisuke*; Kurita, Keisuke
no journal, ,
Neutron imaging was applied to visualize the flow structures in a rectangular spouted bed with stainless-steel beads. The diameter of the stainless-steel beads is 1mm and cadmium particles were put into the bed as the tracer. Neutron transmission images were obtained by a high-speed imaging system at the thermal neutron radiography facility at the research reactor JRR3 of the Japan Atomic Energy Agency. The frame rate was 250 fps, to measure the velocity profiles of the cadmium particles. As a result, the distribution of bed materials and the flow behavior of the cadmium particles were clearly visualized by the neutron imaging. The variation of flow structures with gas flow rate will be discussed.
Harayama, Isao; Kurita, Keisuke; Iikura, Hiroshi; Tsuchikawa, Yusuke; Kai, Tetsuya; Shinohara, Takenao; Matsubayashi, Masahito; Odaira, Naoya*; Ito, Daisuke*; Saito, Yasushi*
no journal, ,
no abstracts in English
