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小野 綾子; 山下 晋; 鈴木 貴行*; 吉田 啓之
Proceedings of 19th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-19) (Internet), 16 Pages, 2022/03
原子力機構では、軽水炉燃料の安全性評価において必須である限界熱流束の評価において、新型燃料設計にかかわる大型モックアップ試験によるコストの削減や、想定外事象に対応するためにモックアップ試験の試験範囲よりも幅広い範囲において、限界熱流束を機構論に基づき評価する研究に着手している。本研究では、機構論的流動解析手法であるJUPITERを用いて、スワールベーンおよびスプリットベーン付きの燃料集合体内の国際ベンチマーク問題を対象とした単相流解析および同体系における二相流解析を実施し、各種ベーンによる流動場および気泡挙動に与える効果、解析における課題の抽出を行った結果を報告する。
大川 富雄*; 森 昌司*; Liu, W.*; 小瀬 裕男*; 吉田 啓之; 小野 綾子
日本原子力学会誌ATOMO
, 63(12), p.820 - 824, 2021/12
原子炉設計における効率的な燃料設計および最適な安全評価のために、機構論に基づいた限界熱流束評価技術が望まれている。この長年の技術課題は、近年の詳細解析技術及び計測技術の体系的統合を段階的に進めることで、打開できる可能性がある。このため本研究専門委員会では、将来的な限界熱流束評価技術の構築に向けて、過去の膨大な研究を精査することで必要な知見を整理する。これらの議論を通して、原子炉における機構論的限界熱流束評価技術に必要な研究課題を提示する。Part2では、これまでの限界熱流束機構に関する基礎研究や限界熱流束の予測手法確立に必須な数値解析手法の発展にふれ、課題提起を行う。
Han, X.*; Shen, X.*; 山本 俊弘*; 中島 健*; 孫 昊旻; 日引 俊*
International Journal of Heat and Mass Transfer, 178, p.121637_1 - 121637_24, 2021/10
被引用回数：7 パーセンタイル：58.99(Thermodynamics)This paper studies the flow regimes, their transitions and the drift-flux correlations in upward gas-liquid two-phase flows in vertical rod bundle flow channels. The flows are classified into 5 flow regimes, namely, bubbly, finely dispersed bubbly, cap-bubbly, churn and annular flows according to their different flow characteristics. Transition criteria between the flow regimes are proposed mechanistically. Those criteria can correctly predict 83% of the existing experimental observation of the flow regime. The drift-flux correlations for the distribution parameter and the drift velocity are also improved. The void fractions predicted by those correlations are compared with the existing experimental data, showing satisfactory agreement with mean relative error of 8%.
岡垣 百合亜; 与能本 泰介; 石垣 将宏; 廣瀬 意育
Fluids (Internet), 6(2), p.80_1 - 80_17, 2021/02
Many thermohydraulic issues about the safety of light water reactors are related to complicated two-phase flow phenomena. In these phenomena, computational fluid dynamics (CFD) analysis using the volume of fluid (VOF) method causes numerical diffusion generated by the first-order upwind scheme used in the convection term of the volume fraction equation. Thus, in this study, we focused on an interface compression (IC) method for such a VOF approach; this technique prevents numerical diffusion issues and maintains boundedness and conservation with negative diffusion. First, on a sufficiently high mesh resolution and without the IC method, the validation process was considered by comparing the amplitude growth of the interfacial wave between a two-dimensional gas sheet and a quiescent liquid using the linear theory. The disturbance growth rates were consistent with the linear theory, and the validation process was considered appropriate. Then, this validation process confirmed the effects of the IC method on numerical diffusion, and we derived the optimum value of the IC coefficient, which is the parameter that controls the numerical diffusion.
吉田 啓之; 上澤 伸一郎
Proceedings of 2020 International Conference on Nuclear Engineering (ICONE 2020) (Internet), 7 Pages, 2020/08
The radioactive aerosol removal equipment is used as one of the safety systems of nuclear reactors. In this equipment, microparticles of aerosol are removed through gas-liquid interfaces of two-phase flow. The mechanism related to the removal of microparticles through the gas-liquid interface is not precise; a numerical evaluation method of performance of aerosol removal equipment is not realized. Then, we have started to construct a numerical simulation method to simulate the removal of microparticles through gas-liquid interfaces. In this simulation method, a detailed two-phase flow simulation code TPFIT is used as the basis of this method. TPFIT adopts an advanced interface tracking method and can simulate interface movement and deformation directly. Also, to simulate the movement of particles, the Lagrangian particle tracking method is incorporated. By combining the interface tracking method, and the Lagrangian particle tracking method, the interaction between interfaces and microparticles can be simulated in detail. To solve the Lagrangian equations of particles, fluid properties and fluid velocity surrounding aerosol particles are evaluated by considering the relative position of particles and gas-liquid interface, to simulate particle movement near the interface. In this paper, we show an outline and preliminary results of this simulation method.
6 rod bundleHan, X.*; Shen, X.*; 山本 俊弘*; 中島 健*; 孫 昊旻; 日引 俊*
International Journal of Heat and Mass Transfer, 144, p.118696_1 - 118696_19, 2019/12
被引用回数：14 パーセンタイル：62.14(Thermodynamics)This paper presents a database of local flow parameters for upward adiabatic air-water two-phase flows in a vertical 66 rod bundle flow channel. The local void fraction, interfacial area concentration (IAC), bubble diameter and bubble velocity vector were measured by using a four-sensor optical probe. Based on an existing state-of-the-art four-sensor probe methodology with the characteristic to count small bubbles, IAC in this study was derived more reliably than those in the existing studies. In addition, bubble velocity vector could be measured by the methodology. Based on this database, flow characteristics were investigated. The area-averaged void fraction and IAC were compared with the predictions from the drift-flux model and the IAC correlations, respectively. The applicability of those to the rod bundle flow channel was evaluated.
吉田 啓之; 上澤 伸一郎; 堀口 直樹; 宮原 直哉; 小瀬 裕男*
Proceedings of 11th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-11) (Internet), 6 Pages, 2018/11
The radioactive aerosol removal equipment is used as one of the safety systems of nuclear reactors. In this equipment, micro particles of aerosol remove through gas-liquid interfaces of two-phase flow. The mechanism related to the removal of micro particles through the gas-liquid interface is not clear, a numerical evaluation method of performance of aerosol removal equipment is not realized. Then, we have started to construct a numerical simulation method to simulate removal of micro particles through gas-liquid interfaces. In this simulation method, detailed two-phase flow simulation code TPFIT is used as the basis of this method. TPFIT adopts an advanced interface tracking method and can simulate interface movement and deformation directly. In addition, to simulate the movement of particles, the Lagrangian particle tracking method is incorporated. By combining the interface tracking method and the Lagrangian particle tracking method, the interaction between interfaces and micro particles can be simulated in detail. To solve the Lagrangian equations of particles, fluid properties and fluid velocity surrounding aerosol particles are evaluated by considering the relative position of particles and gas-liquid interface, to simulate particle movement near the interface. In this paper, outline and preliminary results of this simulation method are shown.
Xiao, Y.*; Shen, X.*; 三輪 修一郎*; 孫 昊旻; 日引 俊*
混相流シンポジウム2018講演論文集(インターネット), 2 Pages, 2018/08
ロッドバンドル体系における二流体モデルの構成式の高度化を図るために、66ロッドバンドル体系における上昇気液二相流実験を実施した。ボイド率や界面積濃度等の局所流動パラメータを2針式光プローブで計測した。計測した断面平均ボイド率と界面積濃度の結果と、既存ドリフトフラックスモデルや界面積濃度相関式から予測した結果と比較した。
Do, V. K.; 山本 昌彦; 田口 茂郎; 久野 剛彦; 駿河谷 直樹
Current Analytical Chemistry, 14(2), p.111 - 119, 2018/00
被引用回数：4 パーセンタイル：15.22(Chemistry, Analytical)本研究では、マイクロチップをベースとした二相流による溶媒抽出と誘導結合プラズマ質量分析装置(ICP-MS)を組み合わせた元素分析システムを構築した。マイクロ流路内の二相流は、コイル状にしたチューブによって圧力バランスを調整することで安定化させた。また、マイクロチップとICP-MSの流体の流速差は、ICP-MSの試料導入部に設けたT字型ミキサ及びバルブを用いて調整した。本システムを用いて、Tcの模擬試料であるReの測定結果、1-20
g/Lの濃度範囲で良好な検量線を得ることができた。試料1mLを使用して求めた定量下限値は0.2g/L、測定に要した時間は1時間以下であった。本件で構築したシステムは、廃液発生量と作業者の放射線被ばくを低減させながら、放射性物質を選択的に測定するための分析法として有効である。
Shen, X.*; 孫 昊旻; Deng, B.*; 日引 俊*; 中村 秀夫
Proceedings of 17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17) (USB Flash Drive), 14 Pages, 2017/09
4センサープローブを用いて、鉛直大口径正方形ダクト内における上向き気泡流の実験的研究を行った。流れ方向3断面における局所界面積濃度、3次元気泡速度ベクトルと気泡径等を計測した。取得したボイド率、局所界面積濃度、3次元気泡速度ベクトルと気泡径等により、流れの挙動に関する有益な情報を提供できるだけでなく、界面積濃度輸送方程式内のソースとシンク項の機構論的モデルの高度化にとって重要なデータベースとなる。
Shen, X.*; Schlegel, J. P.*; 日引 俊*; 中村 秀夫
Proceedings of 2017 Japan-US Seminar on Two-Phase Flow Dynamics (JUS 2017), 6 Pages, 2017/06
Large-diameter (D) channels are extensively used to increase the mass, momentum and heat transport capability of working fluid. Comparing with small-D pipes, two-phase flows in large-D channels show quite different and more complicated flow characteristics, since much larger cap bubbles can exist and interfacial instability prevents the cap bubbles from forming a large stable Taylor bubble. Flow regimes and radial void fraction profiles are also different from those in small-D pipes especially in cap/slug flow regime. The relative velocities between phases are greatly increased. This paper reviews recent progresses in the researches on two-phase flows in large-D channels. The state-of-the-art tool of four-sensor probe may enable classification of two-group bubbles by the measurement of bubble diameter instead of bubble chord length. Databases and most of the updated constitutive equations that cover flow regime transition criteria, drift-flux correlations, interfacial area concentration (IAC) correlations and one- and two-group interfacial area transport equation(s) are summarized and analyzed. Typical multi-dimensional characteristics of flows in large-D channels are presented and their one-dimensional numerical simulations are reviewed. Finally the future research directions are suggested.
4 bundle at 2 MPaLiu, W.; 永武 拓; 柴田 光彦; 高瀬 和之; 吉田 啓之
Transactions of the American Nuclear Society, 114, p.875 - 878, 2016/06
原子力機構では、事故時炉心露出過程を明らかにするための炉内二相水位に深く関連する高温高圧低流量条件におけるボイド率特性の解明及び事故時炉心内二相流解析の予測精度の向上に関する研究を実施している。本報では、高温高圧低流量条件におけるバンドル内ボイド率分布データ及びコード検証するための気泡に関する詳細情報を取得することを目的として、ワイヤーメッシュセンサーを用い、高温高圧条件下でのバンドル内ボイド率データの取得を行っている。試験装置は、99三層式ワイヤーメッシュセンサーを44の模擬バンドル内に、軸方向2カ所に配置したものである。本報では、蒸気-水二相流に対して、1.6MPa(202
C), 2.1MPa(215C)及び2.6MPa(226C)条件で実施した試験により得た、炉心スクラム後を想定した低流量条件でのバンドル内ボイド率分布計測結果について報告する。
Shen, X.*; 孫 昊旻; Deng, B.*; 日引 俊*; 中村 秀夫
Progress in Nuclear Energy, 89, p.140 - 158, 2016/05
被引用回数：22 パーセンタイル：88.83(Nuclear Science & Technology)4センサープローブを用いて、鉛直大口径正方形管内の上昇気液二相流の局所構造を計測した。球形と非球形気泡を区別する4センサープローブの計測手法を適用し、局所3次元気泡速度ベクトル、気泡径と界面積濃度を計測した。液相流量が低い時と高い時、局所ボイド率と界面積濃度はそれぞれ中心ピークと壁ピークの分布を示した。断面内における横方向気泡速度は、断面の対称的な8分の1三角領域内を循環する2次流れの存在を示し、その大きさは液相速度の上昇とともに増加した。本データに対して、既存ドリフトフラックスモデルや界面積濃度の相関式の比較を行い、適応性を検証した。
吉田 啓之; 堀口 直樹; 阿部 豊*
Proceedings of 2015 US-Japan Seminar on Two-Phase Flow Dynamics, 10 Pages, 2015/05
From the viewpoint of protecting a containment and suppressing the diffusion of radioactive materials in accident of nuclear power plants, it is important to develop the device which allows a filtered venting of contaminated high pressure gas. In the filtered venting system that used in European reactors, so called Multi Venturi Scrubbers System is used to realize filtered venting without any power supply. This system is able to define to be composed of Venturi Scrubbers (VS) and a bubble column. In the VS, scrubbing of contaminated gas is promoted by both gas releases through the submerged VS and gas-liquid contact with splay flow. However, the scrubbing mechanism of the VS is understood insufficiently. Therefore, we started numerical and experimental study to understand the two-phase flow behavior in the VS. In this paper, we performed numerical simulations of two-phase flow behavior in the VS by the TPFIT. In the first step, we perform numerical simulations of supersonic flow by the TPFIT to validate the applicability of the TPFIT for high velocity flow in the VS. In the second step, numerical simulation of two-phase flow behavior in the VS including self-priming phenomena. As the results, dispersed flow in the VS was reproduced in the numerical simulation, as same as the visualization experiments.
堀口 直樹; 吉田 啓之; 金川 哲也*; 金子 暁子*; 阿部 豊*
Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 6 Pages, 2015/05
原子炉における炉心溶融を伴うシビアアクシデント時において、放射性物質の拡散を抑制し、かつ格納容器の保護のため除熱および減圧するための手段としてフィルタードベントがある。本研究は、ベンチュリースクラバーを用いたフィルタードベントの作動特性を明らかにすることを目的として、実験ならびに解析を行っている。これまでの研究により、単一ベンチュリースクラバーにおいて、気相流入量がある一定以上になった場合、自吸停止に至る可能性を明らかにした。本報告では、詳細二相流解析コードTPFITを用いて、ベンチュリースクラバー内の二相流解析を行い、自吸現象に対する数値予測を行うと共に、液滴発生のメカニズムについて検討した結果について報告する。
加藤 由幹; 吉田 啓之; 横山 諒太郎*; 金川 哲也*; 金子 暁子*; 文字 秀明*; 阿部 豊*
Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 8 Pages, 2015/05
In this study, visualization experiment for the bubbly flow in a horizontal pipe excited by oscillation acceleration was performed to understand bubbly flow behavior under earthquake acceleration. Liquid pressure was also measured at upstream and downstream of the test section. In addition, to consider detailed effects of pressure gradient on bubble motion, numerical simulation of two-phase flow in horizontal pipe with vibration was performed by a detailed two-phase flow simulation code with an advanced interface tracking method: TPFIT. Based on observed images and calculated results, bubble velocity was evaluated. It was confirmed that the pressure gradient amplitude increased with the increase of the frequency of the table. In addition, it was observed that the bubble velocity amplitude also increases with the increase of the frequency of the table. It was concluded that the bubble motion was strongly affected by the pressure gradient in the test section.
堀口 直樹; 吉田 啓之; 金川 哲也*; 金子 暁子*; 阿部 豊*
Proceedings of 9th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-9) (CD-ROM), 5 Pages, 2014/11
A Multi Venturi Scrubber System (MVSS) is one of the filtered venting devices, and used for existing reactors in Europe. One of the main components of the MVSS is a self-priming Venturi Scrubber (VS). It is considered that a dispersed or dispersed annular flow is formed in the VS by a self-priming phenomena. In the self-priming phenomena, the liquid was suctioned from a surrounding region to the inside of the VS. And a part of the radioactive materials in the gas are eliminated to the liquid through the gas-liquid interface of the dispersed or annular dispersed flow. Therefore, to consider the MVSS operation characteristics, it is important to evaluate the liquid flow rate of the self-priming of the VS including the occurrence condition of the self-priming. In this paper, to understand the self-priming phenomena of the VS for the filtered venting, theoretical preliminary analysis for evaluating liquid flow rate of the self-priming of the VS and experiment to observe self-priming phenomena and measure the liquid flow rare of the self-priming were performed. By comparing these results, we discussed about the mechanism of the self-priming phenomena. As a result, the self-priming phenomena in the VS was observed. In addition, at a higher gas mass flux, the suspension of the self-priming phenomena was confirmed both experimentally and theoretically.
吉田 啓之; 永武 拓; 高瀬 和之; 金子 暁子*; 文字 秀明*; 阿部 豊*
Mechanical Engineering Journal (Internet), 1(4), p.TEP0025_1 - TEP0025_11, 2014/08
In this study, to develop the predictive technology of two-phase flow dynamics under earthquake acceleration, a detailed two-phase flow simulation code with an advanced interface tracking method TPFIT was expanded. In addition, the bubbly flow in a horizontal pipe excited by oscillation acceleration and under the fluctuation of the liquid flow was simulated by using the modified TPFIT. In the results, it was confirmed that the modified TPFIT can predict time dependent velocity distribution around the bubbles and shapes of bubbles qualitatively. The main cause of bubble deformation observed is large shear stress at the lower part of the bubble, and this large shear stress is induced by the velocity difference between the liquid phase and bubble. Moreover, we discussed about the difference between both effects of flow rate fluctuation and structure vibration on two-phase flow. In the results, bubble acceleration of the structure vibration case was larger than that of the flow rate fluctuation case. Finally, it was concluded that unsteady shear stress induced by vibration of the pipe wall was one of the main driving forces of bubble motion in structure vibration case.
吉田 啓之; 玉井 秀定; 大貫 晃; 高瀬 和之; 秋本 肇
Nuclear Engineering and Technology, 38(2), p.119 - 128, 2006/04
日本原子力研究開発機構において開発が進められている超高燃焼水冷却増殖炉の熱設計においては、詳細二相流解析手法により、稠密炉心の除熱性能を評価する。この一環として本研究では、改良界面追跡法を用いた詳細二相流解析コードTPFITの開発を行っている。本報では、解析コードのベクトル並列化を行い、大規模解析に対応させるとともに、解析コード検証解析や稠密炉心を模擬した体系における解析結果を示す。
高瀬 和之; 吉田 啓之; 小瀬 裕男*; 秋本 肇
Computational Fluid Dynamics 2004, p.649 - 654, 2006/00
日本原子力研究開発機構が研究を進めている革新的水冷却炉は減速材の割合を減らして中性子の減速を抑制することで高い転換比が期待できる原子炉であり、炉心には直径13mm程の燃料棒が1mm程度の燃料棒間ギャップ幅で三角ピッチ状に稠密に配置される。このような狭隘流路内の二相流挙動を高温高圧の原子炉条件下で詳細に計測することは困難であることから、著者らは実験データを必要としないシミュレーションだけによる評価法の開発を行っている。本論文では、革新的水冷却炉の炉心燃料集合体1カラム内二相流を対象にして、超高性能計算機による大規模シミュレーションの結果を示す。本研究によって、燃料集合体内の狭隘流路に設置されるスペーサまわりの気相と液相の挙動や燃料棒外表面を薄膜状に流れる液膜挙動などが定量的に明らかになるとともに、シミュレーションを主体とした炉心熱設計手法の実現に対して高い見通しが得られた。
