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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.
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
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
Masaki, Naoto*; Kaneko, Akiko*; Horiguchi, Naoki; Yoshida, Hiroyuki
no journal, ,
During a severe accident in nuclear reactors, melted fuel rods and other materials may fall as liquid jets into the pool of cooling water remaining in the lower head of the pressure vessel. From the viewpoint of preventing accident development, the clarification of cooling and solidification mechanisms with atomization in the cooling water is essential. Many researchers performed experimental and analytical work to understand jet behavior and atomization in a deep pool. In the case of insufficient water depth, i.e., shallow water pool, there are a few reports in both experimental and analytical approaches. The reports of shallow pools show that atomization occurs even after the jet has impacted the bottom wall. However, the mechanism has not been understood. In this study, we assumed that instability due to velocity difference affects the atomization in a shallow-water pool and tried to give a velocity difference to the interface as an agitation using a vortex provided by a stirrer to examine whether the agitation affects atomization. We conducted visualization and measurement experiments using a simulated liquid-liquid two-fluid system in the shallow pool. As a result, an agitation using a vortex occurred in the pool. The number of droplets and the rise time of the number changed increasing the stirrer frequency. This result suggests that the agitation contributed to the atomization.
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.
