Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Horiguchi, Naoki; Yoshida, Hiroyuki; Kaneko, Akiko*; Abe, Yutaka*
Physics of Fluids, 37(3), p.033333_1 - 033333_20, 2025/03
Times Cited Count：0 Percentile：0.00(Mechanics)In a severe accident, as molten fuel is assumed to behave as a wall-impinging jet in a shallow coolant pool, atomize and accumulate as fuel debris, it is important to reveal the atomization mechanisms of the wall-impinging jet. This study aimed to reveal the atomization mechanisms in the vortex-like flow of a wall-impinging jet in a shallow pool of a liquid-liquid system, focusing on droplet formation as an elementary process of atomization. To quantitatively investigate these mechanisms, we applied quantification methods to three-dimensional interfacial data obtained by a previous experimental study using three-dimensional laser-induced fluorescence with index matching. Detailed observations of the spreading behavior of droplets and vortex-like flow, along with quantitative estimations, found out that the vortex-like flow is the dominant source of droplets on the atomization. Further investigations into the forces acting on the vortex-like flow found out the formation and collapse processes of the vortex-like flow. The accelerations of the normal forces acting on the vortex-like flow can be represented by superficial centrifugal acceleration and gravitational acceleration. Our next analysis focused on investigating droplet formation as the elementary process of atomization. The results showed two droplet formation patterns: liquid-film breaking patterns, wherein droplets directly form from the liquid film, and the surfing pattern, wherein droplets form from interfacial waves on the liquid film. Subsequently, the droplet data were grouped using dimensionless numbers and compared with theoretical lines describing the different droplet formation mechanisms. This comparison revealed the mechanisms of droplet formation within the vortex-like flow.
Yuki, Kohei*; Horiguchi, Naoki; Yoshida, Hiroyuki; Yuki, Kazuhisa*
Proceedings of 31st International Conference on Nuclear Engineering (ICONE31) (Internet), 4 Pages, 2024/11
Fuel debris in the Fukushima Nuclear Power Station is cooled under immersion condition. However, in the event of an unexpected decrease in water level, coolant contacts high-temperature fuel debris having porous structure. In this event, although fuel debris needs to be cooled rapidly, thermal behavior at liquid-solid contact, such as capillary phenomenon, remains unclear. In this paper, as basic research, we evaluate droplet evaporation characteristics after contact with metal porous media with small pores less than 1 mm. In experiment, to obtain life time curve of a droplet, bronze or stainless steel porous media having 1, 40, or 100 
m pore diameter are utilized. Experimental results show that Leidenfrost phenomenon is suppressed on the porous surfaces because generated vapor can be discharged from the pores. Further, for bronze porous media, capillary phenomenon is observed as the temperature of the porous media increase because of generation of oxide film having fine structure. On the other hand, due to low wettability of stainless steel porous media, capillary phenomenon does not occur, and the droplet was not sucked and spread into pore. This indicates that rapid cooling by the capillary phenomenon can not be expected if fuel debris has the same characteristics as the stainless steel porous media.
Koyama, Shinichi; Ikeuchi, Hirotomo; Mitsugi, Takeshi; Maeda, Koji; Sasaki, Shinji; Onishi, Takashi; Tsai, T.-H.; Takano, Masahide; Fukaya, Hiroyuki; Nakamura, Satoshi; et al.
Hairo, Osensui, Shorisui Taisaku Jigyo Jimukyoku Homu Peji (Internet), 216 Pages, 2023/11
In FY 2021 and 2022, JAEA perfomed the subsidy program for "the Project of Decommissioning and Contaminated Water Management (Development of Analysis and Estimation Technology for Characterization of Fuel Debris (Development of Technologies for Enhanced Analysis Accuracy, Thermal Bahavior Estimation, and Simplified Analysis of Fuel Debris)" started in FY 2021. This presentation material summarized the results of the project, which will be available shortly on the website of Management Office for the Project of Decommissioning, Contaminated Water and Treated Water Management.
Horiguchi, Naoki; Yoshida, Hiroyuki; Kaneko, Akiko*; Abe, Yutaka*
Nihon Kikai Gakkai Kanto Shibu Dai-29-Ki Sokai, Koenkai Koen Rombunshu (Internet), 5 Pages, 2023/10
To elucidate the behavior of molten fuels as a liquid jet in a shallow pool, which is assumed in a core meltdown accident of an LWR, and develop the evaluation method, we investigated the behavior of the vortical liquid film of the simulated wall-impinging liquid jet using 3-dimensional interface shape data obtained by the experiment in a liquid-liquid system.
Horiguchi, Naoki; Yoshida, Hiroyuki; Kaneko, Akiko*; Abe, Yutaka*
Physics of Fluids, 35(7), p.073309_1 - 073309_17, 2023/07
Times Cited Count：3 Percentile：43.73(Mechanics)The atomization of a liquid jet in an immiscible liquid-liquid system is significant for the safety in the nuclear industry field. The Japan Atomic Energy Agency has developed an evaluation method of a melt fuel behavior as a liquid jet in an immiscible liquid-liquid system for subsequence using mechanistic numerical simulation and has investigated liquid jet behavior in a shallow pool through numerical simulations and experiments. The paper clarifies the atomization mechanism in the wall-impinging liquid jet. Herein, the atomization behavior in the wall-impinging liquid jet in a shallow pool in an immiscible liquid-liquid system was studied in terms of droplet formation and flow field using numerical simulation and the dispersed-phase tracking method. The results show that the droplet formation in the liquid film flow of the wall-impinging liquid jet had the three patterns, and we obtained the droplet properties immediately after droplet formation and developed the theoretical criterion regions using the dimensionless numbers for droplet formation. We characterized the patterns by comparing them with the regions and elucidated the droplet formation mechanisms depending on their sources. Moreover, we elucidated that the relationship between droplet formation as the local behaviors of the jet and atomization as the whole behavior.
Horiguchi, Naoki; Yoshida, Hiroyuki; Kitatsuji, Yoshihiro; Hasegawa, Makoto*; Kishimoto, Tadafumi*
Proceedings of 30th International Conference on Nuclear Engineering (ICONE30) (Internet), 7 Pages, 2023/05
From the viewpoint of energy security in Japan and reduction of the environmental load, continuous operation of light water reactors is essential. Since a pH adjuster with enriched Li-7 ions is required for water quality control on PWR, the development of Li-7 enrichment technology is one of the key issues. The multi-channel counter-current electrophoresis (MCCCE) method has been developed as the technology with a low environmental load. To put this method into practical use, it is necessary to understand Li-7 ion behavior in the channel flow and optimize the experimental condition to separate Li-7 and its isotope. In this paper, to understand Li-7 ion behavior in a single channel of the experimental apparatus, a numerical simulation method based on a computational fluid dynamics (CFD) code with a particle tracking method, TPFIT-LPT, was developed. In the method, the motion of multiple ions under the electric field was simulated as a particle with an added velocity by the electric field. The difference in the isotopes was represented by changing of the magnitude of the added velocity. We also considered that although it is impossible to measure the behavior of each ion, it is important to measure the flow velocity of the bulk fluid for the validation of the numerical simulation. We developed a lab-scale experimental apparatus in which the single channel of the actual apparatus was simplified to measure the flow velocity by Particle Image Velocimetry (PIV). We set a pulsation flow condition on the lab-scale experiment, which is one of difficult conditions for the numerical simulation, and measured the velocity. As the result, we confirmed that the pulsation flow was reproduced. We set the measured data as the inlet boundary condition of the numerical simulation and conducted it. As the numerical result, we confirmed the ions affected by the electric field moved upstream with pulsation. We also confirmed the effect of the electric field on the motion of the isotope.
Yoshida, Hiroyuki; Horiguchi, Naoki; Furuichi, Hajime*; Katono, Kenichi*
Proceedings of 30th International Conference on Nuclear Engineering (ICONE30) (Internet), 7 Pages, 2023/05
Yoshida, Hiroyuki; Horiguchi, Naoki
Nihon Kikai Gakkai Kanto Shibu Dai-29-Ki Sokai, Koenkai Koen Rombunshu (Internet), 5 Pages, 2023/03
To reduce contaminated water at the Fukushima Daiichi Nuclear Power Plant and consider the fuel debris retrieval method, a numerical simulation method is required to evaluate the effects of water injection. Then, we are developing a multiphase CFD simulation method based on the three-dimensional two-fluid model to evaluate thermal-hydraulic behavior in the primary containment vessel. The numerical simulation method was developed by introducing the required functions into the ACE-3D. This paper presents an overview of the porous model introduced to the ACE-3D to evaluate thermal-hydraulic behavior in fuel debris. In addition, we performed the numerical simulation for the Fukushima Daiichi Nuclear Power Plant unit 2 under the condition in which water injection stopped. And we compared the analysis results by the modified ACE-3D with more detailed three-dimensional CFD results by JUPITER.
Horiguchi, Naoki; Yoshida, Hiroyuki; Kaneko, Akiko*; Abe, Yutaka*
Proceedings of 12th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS12) (Internet), 6 Pages, 2022/10
For safety evaluation of nuclear reactors in severe accidents, it is important to estimate physical quantities of fragments generated from the molten fuel jet, which falls in a pool and breaks up. The evaluation method has been developed for the behavior as liquid jet with hydrodynamic interaction including fuel coolant interaction (FCI). In case of a shallow pool assumed in ex-vessel, the molten fuel jet is assumed to behave as wall-impinging liquid jet and to form liquid film flow spreading on the floor with/without fragmentation. In our research, focusing on hydrodynamic interaction and the transient 3-dimensional spreading on the floor, we have developed the evaluation method by numerical simulation using the two-phase flow simulation code with interface tracking method (TPFIT) developed by JAEA and, the experimental method using the 3D-LIF method in liquid-liquid system for the validation data. In our previous studies, we investigated the wall-impinging liquid jet behavior with fragmentation and observed that the liquid film flow had some characteristic parts transiently. Since it indicates that the quantities change depending on the parts and affect the safety evaluation, it is important to measure the quantities of the fragments generated from each part. This paper explains the measurement of the physical quantities of the fragments generated from each part of the wall-impinging liquid jet in a shallow pool for the validation of the numerical simulation. We conducted an experiment with the 3D-LIF method and segmented the experimental data based on the fragmentation point over the liquid film flow using the dispersed phase tracking method, developed by JAEA. Then, we measured the diameter and amount of the fragments from the segmented experimental data and investigated their changing trend.
Tobita, Daiki*; Monji, Hideaki*; Yamashita, Susumu; Horiguchi, Naoki; Yoshida, Hiroyuki; Sugawara, Takanori
Proceedings of 12th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS12) (Internet), 5 Pages, 2022/10
Horiguchi, Naoki
Nihon Genshiryoku Gakkai Netsu Ryudo Bukai Nyusu Reta (Internet), (101), p.9 - 10, 2022/09
no abstracts in English
Yamamura, Sota*; Fujiwara, Kota*; Honda, Kota*; Yoshida, Hiroyuki; Horiguchi, Naoki; Kaneko, Akiko*; Abe, Yutaka*
Physics of Fluids, 34(8), p.082110_1 - 082110_13, 2022/08
Times Cited Count：3 Percentile：30.82(Mechanics)Liquid spreading and atomization due to jet impingement in liquid-liquid systems are considered to be crucial for understanding the cooling behavior of high-temperature molten material in a shallow water pool. This phenomenon takes place when a liquid jet enters a pool filled with other immiscible liquid. The jet spreads radially after impinging on the floor while forming a thin liquid film and atomizing droplets. In this paper, we explain the result to quantify the unsteady three-dimensional behavior of the spreading jet by the employment of 3D-LIF measurements and 3-dimensional reconstruction. Under high flow velocity conditions, the phenomena of hydraulic jump and atomization of the liquid film occurred along with the spreading. To evaluate the spreading behavior, a comparison of the jump radius position of the liquid-liquid system as the representative value was made with the one calculated by the existing theory of a gas-liquid system. As the result, the spreading of the liquid film in the liquid-liquid system was suppressed compared with that in the gas-liquid system. Furthermore, the PTV method was successfully used to measure the velocity boundary layer and velocity profile in the liquid film, which are important factors that affect the spreading mechanism of the liquid film. These results revealed that in liquid-liquid systems, shear stress at the liquid-liquid interface causes a decrease in the flow velocity and suppressed the development of the velocity boundary layer. Also, to evaluate the atomization behavior, the number and diameter distribution of the droplets were measured from the acquired 3-dimensional shape data of the jet. As the result, the number of droplets increased with the flow velocity. Based on these results, we concluded that the spreading of the liquid film is affected by such atomization behavior.
Yoshida, Hiroyuki; Horiguchi, Naoki; Ono, Ayako; Furuichi, Hajime*; Katono, Kenichi*
Proceedings of 29th International Conference on Nuclear Engineering (ICONE 29) (Internet), 7 Pages, 2022/08
Horiguchi, Naoki; Yoshida, Hiroyuki; Yamamura, Sota*; Fujiwara, Kota*; Kaneko, Akiko*; Abe, Yutaka*
Proceedings of 19th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-19) (Internet), 14 Pages, 2022/03
Koyama, Shinichi; Nakagiri, Toshio; Osaka, Masahiko; Yoshida, Hiroyuki; Kurata, Masaki; Ikeuchi, Hirotomo; Maeda, Koji; Sasaki, Shinji; Onishi, Takashi; Takano, Masahide; et al.
Hairo, Osensui Taisaku jigyo jimukyoku Homu Peji (Internet), 144 Pages, 2021/08
JAEA performed the subsidy program for the "Project of Decommissioning and Contaminated Water Management (Development of Analysis and Estimation Technology for Characterization of Fuel Debris (Development of Technologies for Enhanced Analysis Accuracy and Thermal Behavior Estimation of Fuel Debris))" in 2020JFY. This presentation summarized briefly the results of the project, which will be available shortly on the website of Management Office for the Project of Decommissioning and Contaminated Water Management.
Gou
llo, M.*; Hokkinen, M.*; Suzuki, Eriko; Horiguchi, Naoki; Barrachin, M.*; Cousin, F.*
Progress in Nuclear Energy, 138, p.103818_1 - 103818_10, 2021/08
Times Cited Count：7 Percentile：56.80(Nuclear Science & Technology)The present work aimed to study the transport of caesium iodide particles through a Thermal Gradient Tube (TGT) from 1023 K to 453 K. Retention inside the tube was evaluated for laminar flowrates composed of argon and steam. Higher retention of particles was highlighted for the experiments using higher steam content and lower flowrate. The second phase of the experiment aimed at identifying the possible revaporization or/and resuspension processes after the deposition. Three atmosphere compositions (Ar/H
O, Ar/H and Ar/Air) were investigated. The particles removed from what was deposited on the surface walls during the sampling phase exhibited a similar GMD in Ar/HO and Ar/H and a bigger diameter in Ar/Air. The experimental results were then analysed with the SOPHAEROS module of the ASTEC code. Overall, the results obtained during the first phase were in agreement with the measured experimental results and during second phase led to no resuspension process.
Miyahara, Naoya; Miwa, Shuhei; Goullo, M.*; Imoto, Jumpei; Horiguchi, Naoki; Sato, Isamu*; Osaka, Masahiko
Journal of Nuclear Science and Technology, 57(12), p.1287 - 1296, 2020/12
Times Cited Count：9 Percentile：65.08(Nuclear Science & Technology)In order to clarify the cesium iodide (CsI) transport behavior with a focus on the mechanisms of gaseous iodine formation in the reactor coolant system of LWR under a severe accident condition, a reproductive experiment of CsI transport behavior was conducted using a facility equipped with a thermal gradient tube. Various analyses on deposits and airborne materials during transportation could elucidate two mechanisms for the gaseous iodine formation. One was the gaseous phase chemical reaction in Cs-I-O-H system at relatively high-temperature region, which led to gaseous iodine transport to the lower temperature region without any further changes in gas species due to the kinetics limitation effects. The other one was the chemical reactions related to condensed phase of CsI, namely those of CsI deposits on walls with surface of stainless steel to form CsCrO
compound and CsI aerosol particles with steam, which were newly found in this study.
Miwa, Shuhei; Nakajima, Kunihisa; Suzuki, Chikashi; Rizaal, M.; Suzuki, Eriko; Horiguchi, Naoki; Osaka, Masahiko
Proceedings of Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020 (SNA + MC 2020), p.253 - 260, 2020/12
We have proceeded the fundamental study for the improvement of the evaluation of fission product (FP) chemistry and the treatment of fine space resolution which are main issues for the evaluation of FP behaviors in a severe accident (SA). We have been developing FP chemistry database named ECUME for the improvement of SA analysis codes. We prepared thermodynamic data for Cs compounds which is no experimental data available by computational approach. Regarding the space resolution issue, we have been developing analysis tool named CHASER based on 3D-CFD code with the model for FP chemistry. More accurate evaluation of FP behavior can be achieved by incorporating ECUME to the CHASER.
Suzuki, Takayuki*; Yoshida, Hiroyuki; Horiguchi, Naoki; Yamamura, Sota*; Abe, Yutaka*
Proceedings of 2020 International Conference on Nuclear Engineering (ICONE 2020) (Internet), 7 Pages, 2020/08
Miwa, Shuhei; Nakajima, Kunihisa; Miyahara, Naoya; Nishioka, Shunichiro; Suzuki, Eriko; Horiguchi, Naoki; Liu, J.; Miradji, F.; Imoto, Jumpei; Afiqa, B. M.; et al.
Mechanical Engineering Journal (Internet), 7(3), p.19-00537_1 - 19-00537_11, 2020/06
We constructed the fission product (FP) chemistry database named ECUME for LWR severe accident. This version of ECUME is equipped with dataset of the chemical reactions and their kinetics constants for the reactions of cesium(Cs)-iodine(I)-boron(B)-molybdenum(Mo)-oxygen(O)-hydrogen(H) system in gas phase, the elemental model for the high temperature chemical reaction of Cs with stainless steel applied as the structural material in a reactor, and thermodynamic data for CsBO vapor species and solids of CsSiO
and CsFeSiO for these chemical reactions. The ECUME will provide estimation of Cs distribution due to the evaluation of effects of interaction with BWR control material B and stainless steel on Cs behavior in the Fukushima Daiichi Nuclear Power Station.
