Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Uesawa, Shinichiro; Yoshida, Hiroyuki
Journal of Nuclear Science and Technology, 61(11), p.1438 - 1452, 2024/11
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)We developed a deep learning-based bubble detector with a Shifted window Transformer (Swin Transformer) to detect and segment individual bubbles among overlapping bubbles. To verify the performance of the detector, we calculated its average precision (AP) with different number of training images. The mask AP increased with the increase in the number of training images when there were less than 50 images but remained constant when there were more than 50 images. It was observed that the AP for the Swin Transformer and ResNet were almost the same when there were more than 50 images; however, when few training images were used, the AP of the Swin Transformer were higher than that of the ResNet. Furthermore, with regard to the increase in void fraction, the AP of the Swin Transformer showed a decrease similar to that in the case of the ResNet; however, for few training images, the AP of the Swin Transformer was higher than that of the ResNet in all void fractions. Moreover, we confirmed the detector trained with synthetic bubble images was able to segment overlapping bubbles and deformed bubbles in a bubbly flow experiment. Thus, we verified that the new bubble detector with Swin Transformer provided higher AP than the detector with ResNet for fewer training images.
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.
Ono, Ayako; Yamashita, Susumu; Suzuki, Takayuki*; Yoshida, Hiroyuki
Proceedings of 19th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-19) (Internet), 16 Pages, 2022/03
JAEA is developing the methodology to predict the critical heat flux based on a mechanism in order to reduce the cost for full mock-up test. The evaluation method based on a mechanism is expected to be able to predict in the wide range of parameter under the unexpected conditions including the severe accident. In this study, the JUPITER code developed by JAEA is examined to apply for the two-phase flow simulation of LWR fuel assembly with the spacer grid. The benchmark data of single-phase flow in the bundle with the spacers by KAERI were used to validate the simulation result by JUPITER. Moreover, the single-phase flow simulation was conducted by another simulation method, STAR-CCM+, as a supplemental analysis to consider the effect of the different simulation methods. Finally, the two-phase flow simulation for the bundle with the spacer was conducted by JUPITER. The effect of the spacer with a vane on the bubble behavior is discussed.
Okawa, Tomio*; Mori, Shoji*; Liu, W.*; Ose, Yasuo*; Yoshida, Hiroyuki; Ono, Ayako
Nihon Genshiryoku Gakkai-Shi ATOMO
, 63(12), p.820 - 824, 2021/12
The evaluation method of the critical heat flux based on the mechanism is needed for the efficient design and development of fuel in reactors and the appropriate safety evaluation. In this paper, the current researches relating to the mechanism of the critical heat flux are reviewed, and the issue to be considered in the future are discussed.
Han, X.*; Shen, X.*; Yamamoto, Toshihiro*; Nakajima, Ken*; Sun, Haomin; Hibiki, Takashi*
International Journal of Heat and Mass Transfer, 178, p.121637_1 - 121637_24, 2021/10
Times Cited Count：13 Percentile：68.88(Thermodynamics)Okagaki, Yuria; Yonomoto, Taisuke; Ishigaki, Masahiro; Hirose, Yoshiyasu
Fluids (Internet), 6(2), p.80_1 - 80_17, 2021/02
Yoshida, Hiroyuki; Uesawa, Shinichiro
Proceedings of 2020 International Conference on Nuclear Engineering (ICONE 2020) (Internet), 7 Pages, 2020/08
6 rod bundleHan, X.*; Shen, X.*; Yamamoto, Toshihiro*; Nakajima, Ken*; Sun, Haomin; Hibiki, Takashi*
International Journal of Heat and Mass Transfer, 144, p.118696_1 - 118696_19, 2019/12
Times Cited Count：18 Percentile：68.89(Thermodynamics)Yoshida, Hiroyuki; Uesawa, Shinichiro; Horiguchi, Naoki; Miyahara, Naoya; Ose, Yasuo*
Proceedings of 11th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-11) (Internet), 6 Pages, 2018/11
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 66 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.
Do, V. K.; Yamamoto, Masahiko; Taguchi, Shigeo; Kuno, Takehiko; Surugaya, Naoki
Current Analytical Chemistry, 14(2), p.111 - 119, 2018/00
Times Cited Count：4 Percentile：13.88(Chemistry, Analytical)A direct coupling of two-phase flow solvent extraction microfluidics with ICP-MS for element-selective analysis is successfully established. Two-phase flow in microchannels of two combined glass chips for continuous extraction and back-extraction is stabilized through balancing the pressure by using an external coiled tube that functions as a flow resistor. The difference of fluid flow rate between microchannels and ICP-MS is adjusted by a proposed interface system including T-junction mixer and a switching valve. An online measurement of rhenium is successfully demonstrated. The calibration curve for Re is carried out in the range of 1 
g/L to 20 g/L. The limit of detection is 0.2 g/L with a needed sample volume of one milliliter. Total time including extraction, back-extraction, and measurement is less than one hour. The development of the online coupling is a first step towards future applications to the selective measurement of highly radioactive elements.
Shen, X.*; Sun, Haomin; Deng, B.*; Hibiki, Takashi*; Nakamura, Hideo
Proceedings of 17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17) (USB Flash Drive), 14 Pages, 2017/09
An experimental study on the upward bubbly air-water flows in a vertical large-diameter square duct have been performed by using four-sensor probes. The four-sensor probe were applied in the local measurements at 3 axial positions along the flow direction to obtain interfacial area concentration, 3-D bubble velocity vector and bubble diameter. The obtained void fraction, interfacial area concentration, 3-D bubble velocity vector and bubble diameter provided valuable insight into the flow structure and will serve as a valuable database to develop the mechanistic models for interfacial area transport equation sources and sinks.
Shen, X.*; Schlegel, J. P.*; Hibiki, Takashi*; Nakamura, Hideo
Proceedings of 2017 Japan-US Seminar on Two-Phase Flow Dynamics (JUS 2017), 6 Pages, 2017/06
4 bundle at 2 MPaLiu, W.; Nagatake, Taku; Shibata, Mitsuhiko; Takase, Kazuyuki; Yoshida, Hiroyuki
Transactions of the American Nuclear Society, 114, p.875 - 878, 2016/06
To contribute to the clarification of the Fukushima Daiichi Accident, JAEA is working on getting instantaneous void fraction distribution data in steam water two - phase flow in rod bundle geometry under high pressure, high temperature condition, with using Wire Mesh Sensor (WMS) developed at JAEA for high pressure, high temperature condition, focusing on the low flow rate condition after the reactor scram. This paper reports the experimental results for the measured void fraction distribution in steam vapor two-phase flow in a 4 4 bundle under 1.6 MPa (202 
C), 2.1 MPa (215 C) and 2.6 MPa (226 C) conditions. The data is expected to be used in the validation of the detailed two-phase flow codes TPFIT and ACE3D developed at JAEA. The time and space averaged void fraction data is also expected being used in the validation of the drift flux models implemented in the two fluids codes, such as TRACE code.
Shen, X.*; Sun, Haomin; Deng, B.*; Hibiki, Takashi*; Nakamura, Hideo
Progress in Nuclear Energy, 89, p.140 - 158, 2016/05
Times Cited Count：24 Percentile：89.96(Nuclear Science & Technology)An experimental study was performed on the local structure of upward air-water two-phase flow in a vertical large diameter square duct by using a four-sensor probe. The four-sensor probe method classifying spherical and non-spherical bubbles was applied as a key measurement way to obtain local parameters such as 3-D bubble velocity vector, bubble diameter and interfacial area concentration. Both the local void fraction and interfacial area concentration indicated radial core-peak and wall-peak distributions at low and high liquid flow rates respectively. The 2 components of the bubble velocity vector in the cross-section revealed that there exists a rotating secondary flow in the octant symmetric triangular area and the magnitude of the rotating secondary flow increases with the liquid flow rate. Some of constitutive correlations of drift-flux model and interfacial area concentration are reviewed to study their predictabilities against the present data.
Yoshida, Hiroyuki; Horiguchi, Naoki; Abe, Yutaka*
Proceedings of 2015 US-Japan Seminar on Two-Phase Flow Dynamics, 10 Pages, 2015/05
Kato, Yuki; Yoshida, Hiroyuki; Yokoyama, Ryotaro*; Kanagawa, Tetsuya*; Kaneko, Akiko*; Monji, Hideaki*; Abe, Yutaka*
Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 8 Pages, 2015/05
Horiguchi, Naoki; Yoshida, Hiroyuki; Kanagawa, Tetsuya*; Kaneko, Akiko*; Abe, Yutaka*
Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 6 Pages, 2015/05
From the viewpoint of protecting containment and suppressing diffusion of the radioactive materials at severe accidents of nuclear power plant, it is important to install filtered venting devices to permit release of high pressure pollutant gas to the atmosphere by eliminating radioactive materials in the gas. A Multi Venturi Scrubber System (MVSS) is one of the devices for the filtered venting, and is used to realize filtered venting without any power supply. The MVSS is composed of a "Venturi Scrubbers" part and a "bubble column" part. In the Venturi Scrubbers part of the MVSS, there are hundreds of the Venturi scrubbers (VS). In an operation mode of the MVSS, the radioactive materials are eliminated through the gas-liquid interface from the pollutant gas to the liquid phase of a dispersed flow in the VS and a bubbly flow in the bubble column part. In the VS, the dispersed flow is formed from the liquid, which is suctioned through the hole for suction (called self-priming). In previous studies, an evaluation method to evaluate the liquid flow rate by the self-priming was developed. However, to develop evaluation methods of performance of the VSs, the two-phase flow behavior must be investigated, including droplet size and velocity difference of liquid and gas phases. Two-phase flow behavior in the VS is complicated, and it is difficult to estimate two-phase flow behavior of the VS by only experimental procedures. In this study, to investigate the hydraulic behavior of the VS, we tried to apply a detailed numerical simulation method of two-phase flow to the numerical simulation of the VS. In the simulation, TPFIT developed in JAEA was used as the detailed numerical simulation method. In this paper, we performed the numerical simulation air-water two-phase flow in the of the lab scale VS by the TPFIT, and numerical results were compared with experimental results.
Horiguchi, Naoki; Yoshida, Hiroyuki; Kanagawa, Tetsuya*; Kaneko, Akiko*; Abe, Yutaka*
Proceedings of 9th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-9) (CD-ROM), 5 Pages, 2014/11
Yoshida, Hiroyuki; Nagatake, Taku; Takase, Kazuyuki; Kaneko, Akiko*; Monji, Hideaki*; Abe, Yutaka*
Mechanical Engineering Journal (Internet), 1(4), p.TEP0025_1 - TEP0025_11, 2014/08
