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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.
Kimura, Fumihito*; Yamamura, Sota*; Fujiwara, Kota*; Yoshida, Hiroyuki; Saito, Shimpei*; Kaneko, Akiko*; Abe, Yutaka*
Nuclear Engineering and Design, 389, p.111660_1 - 111660_11, 2022/04
Times Cited Count：3 Percentile：66.21(Nuclear Science & Technology)Horiguchi, Naoki; Yamamura, Sota*; Yoshida, Hiroyuki; Abe, Yutaka*
no journal, ,
Specific measurement methods have been developed to understand multi-phase thermal-hydraulic behavior. By using these methods, we can obtain time series two and 3-dimensional spatial interface data of phases. These data are useful for providing validation data for advanced simulation methods based on multi-fluid computation fluid dynamics. For example, to understand FCI (fuel coolant interaction) behavior, specific measurements for fragments (dispersed phase) generated from the jet were measured, and interface and size of fragments were successfully evaluated. However, 3-dimensional data for velocity was not assessed, because there is no tracking method for individual dispersed phases like a tracking method of PTV (particle tracking velocimetry), which using time series 2-dimensional data. In this paper, we developed the dispersoid phase tracking method based on time series 3-dimensional interface data. To check the applicability of this method for 3-dimensional interface data, we used detailed two-phase simulation data by using TPFIT. In these data, there are 3-dimensional data of both interface and velocity distribution. Then, we can evaluate the correct dispersed phase velocity, and we can consider the accuracy of the developed method precisely. In this paper, we applied the developed method to simplified two-phase flow. The simplified flow means not to include coalescence and fragmentation of dispersoids. As a result, the tracking of one dispersoid performed successfully, but a standard deviation of the measuring error increased with the decrease of cell number of the dispersoid.
Horiguchi, Naoki; Yamamura, Sota*; Fujiwara, Kota*; Kaneko, Akiko*; Yoshida, Hiroyuki
no journal, ,
no abstracts in English
Horiguchi, Naoki; Yoshida, Hiroyuki; Kaneko, Akiko*; Abe, Yutaka*
no journal, ,
JAEA has developed the evaluation method of a wall-impinging liquid jet in a shallow pool in a liquid-liquid system by numerical simulation. As a part of the development, to clarify the generation mechanism of the fragments, we identified the primary generation position of the fragments by post-processing the 3-dimensional interface shape data of the liquid jet using the 3D-LIF method and investigated the relationship between the generation position and the liquid film structure of the jet.
