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Matsushita, Kentaro; Ezure, Toshiki; Imai, Yasutomo*; Fujisaki, Tatsuya*; Tanaka, Masaaki
Nihon Kikai Gakkai Kanto Shibu Ibaraki Koenkai 2021-Nendo Koen Rombunshu (Internet), 4 Pages, 2021/08
For evaluation of gas entrainment phenomenon at free surface in reactor vessel of sodium-cooled fast reactor, the gas entrainment evaluation tool named "Stream Viewer" has been developed. In Stream Viewer, depth of surface vortex dimple is predicted by calculating pressure decrease at the vortex center using velocity distribution around the vortex and Burgers vortex model. In this report, a method to identify continuous vortex center lines from a velocity distribution is newly developed. It becomes possible to evaluate three-dimensional distribution of pressure decrease along vortex center line. Then, the method is validated by applying Stream Viewer to an open channel experiment. As the result, it was confirmed that vortex center lines were successfully identified by the improved Stream Viewer. Moreover, it was also shown that the evaluation accuracy of gas entrainment was expected to be improved by considering distribution of pressure decrease along vortex center line.
Matsushita, Kentaro; Fujisaki, Tatsuya*; Ezure, Toshiki; Tanaka, Masaaki; Uchida, Mao*; Sakai, Takaaki*
Keisan Kogaku Koenkai Rombunshu (CD-ROM), 26, 6 Pages, 2021/05
For the gas entrainment vortex at the free surface in sodium-cooled fast reactors, development of the numerical analysis method to evaluate amount of the gas entrainment from the free surface has been developing. In this paper, the automatic creation of analysis meshes which can suppress the calculation cost while maintaining the prediction accuracy of the vortex shape is investigated, and the adaptive mesh refinement (AMR) method is examined to the creation of analysis mesh applying to the unsteady vortex system. The refined mesh based on the criterion evaluated by vorticity, Q-value as second invariant of the velocity and the discriminant for the eigen equation of the velocity gradient tensor is considered, and it found that the AMR method based on Q-value can refine the analysis meshes most efficiently.
Ito, Kei; Kunugi, Tomoaki*; Ohshima, Hiroyuki
no journal, ,
no abstracts in English
Ito, Kei; Koizumi, Yasuo*; Ohshima, Hiroyuki; Kawamura, Takumi*
no journal, ,
The authors are developing a high-precision CFD code with an enhanced interface tracking method to simulate the gas entrainment (GE) phenomena in sodium-cooled fast reactors (SFRs). The GE in SFRs is characterized by an elongated interfacial dent (gas core) along the vortex core and the bubble pinch-off at the tip of the gas core. The authors have developed physics-basis algorithms which model accurately the interfacial shape (gradient and curvature) and the mechanical balance condition at an interface. In this paper, a simple experiment of the GE is simulated to validate the developed code. The simulation result of the bubble pinch-off and the entrained flow rate shows good agreement with the experimental data, that is, the developed simulation code can be applicable to the evaluation of the GE in SFRs.
Matsushita, Kentaro; Ito, Kei*; Ezure, Toshiki; Tanaka, Masaaki
no journal, ,
A numerical simulation code named SYRENA has been developed in JAEA to analyze the behavior of entrained bubbles and dissolved gas in the primary coolant of sodium-cooled fast reactor (SFR). In the present study, a flow network model for a pool-type SFR was newly developed in SYRENA and the non-condensable gas behavior in the pool type SFR was analyzed. A dipped-plate (D/P) model was introduced into the flow network to investigate influences of D/P installation on the non-condensable behavior in the pool-type reactor. A parametric study was performed on the exchange flow rate through the D/P and the gas entrainment rate at the free surface existing above the D/P. The non-condensable gas behavior under various flow conditions, e.g. gas entrainment rate condition, was obtained. Especially, it was observed that the bubble volume in the primary coolant system changed with the exchange flow rate though the change ratio is dependent on the gas entrainment.
Nakamura, Hironori*; Uchita, Masato*; Hayakawa, Satoshi*; Matoba, Ichiyo*; Watanabe, Osamu*; Onoda, Yuichi; Tanaka, Masaaki
no journal, ,
no abstracts in English
Matsushita, Kentaro; Ezure, Toshiki; Imai, Yasutomo*; Fujisaki, Tatsuya*; Tanaka, Masaaki
no journal, ,
In safety design of sodium-cooled fast reactor, generation of a cover gas entrainment vortex at free surface in upper plenum is an issue. It is necessary to evaluate gas entrainment vortex by numerical analysis, and gas entrainment amount evaluation tool "Stream Viewer" based on velocity distribution obtained by numerical analysis is developed. In this report, as a part of the development of Stream Viewer, evaluation method to identify vortex center line from free surface is examined to evaluate three dimensional behavior of gas entrainment vortex. The evaluation method was applied to an open channel water test in which an wake vortex is generated unsteadily from the plate. It was confirmed that vortex center line can be identified and a vortex that propagates to downstream and gas core grows can be distinguished from a vortex in which gas core does not grow by evaluation method of the vortex center line.
Torikawa, Tomoaki*; Odaira, Naoya*; Ito, Daisuke*; Ito, Kei*; Saito, Yasushi*; Matsushita, Kentaro; Ezure, Toshiki; Tanaka, Masaaki
no journal, ,
On free surface of a sodium cooled fast reactor, gas entrainment can be caused by free surface vortices, which may result in disturbance in core power. It is important to develop an evaluation model to predict accurately entrained gas flow rate. In this study, the effect of pressure gradient in vortex axis direction on the gas entrainment flow rate is investigated in a simple gas experimental apparatus, in which upper and lower tanks are connected by a suction pipe. As a result, it was observed that there are two flow regime: swirling annular flow regime shows the tendency that only the gas entrainment flow rate increases with almost constant pressure gradient, then, when liquid plug is induced by the development of free surface disturbance, the gas entrainment flow rate increases as the pressure gradient increases. In addition, it was confirmed that the transformation of those two flow regimes is advanced by higher liquid level in the upper tank.
Matsushita, Kentaro; Ezure, Toshiki; Imai, Yasutomo*; Tanaka, Masaaki
no journal, ,
Japan Atomic Energy Agency (JAEA) is developing AI-aided advanced reactor life cycle optimization method, ARKADIA, in order to support the development of various reactor systems, including sodium-cooled fast reactors (SFRs). One of the important thermal-hydraulic issues in SFR design is the suppression of cover gas entrainment caused by dip vortices in the free surface of the upper plenum of the reactor, and JAEA is developing gas entrainment evaluation system centered on the gas entrainment evaluation tool, StreamViewer, in ARKADIA. In this report, the overview of gas entrainment evaluation system in ARKADIA and the development status of StreamViewer are reported. In addition, the results of applying StreamViewer to the analysis results of the water flow test system and confirming that it is possible to evaluate the gas entrainment phenomenon are reported.
Matsushita, Kentaro; Ezure, Toshiki; Imai, Yasutomo*; Fujisaki, Tatsuya*; Tanaka, Masaaki
no journal, ,
In the sodium-cooled fast reactors, evaluation of cover gas entrainment (GE) by dip vortices at the free surface in the upper plenum of reactor vessel is important. In this study, GE evaluation model, including the identification of vortex center lines between free surface and suction port from the flow velocity distribution obtained by three-dimensional analysis, the calculation of pressure decrease distribution along vortex center line, and the comparison of pressure decrease and the hydrostatic pressure, was investigated. The analyses for GE experiments in a rectangular flow channel were performed by changing the inlet flow velocity condition, and this evaluation model was applied to the flow velocity distribution obtained from the analysis results. As a result, it was confirmed that the phenomenon in which the occurrence of GE increased as the inlet flow velocity increased was reproduced as in the experimental results.
Ito, Kei*; Odaira, Naoya*; Ito, Daisuke*; Saito, Yasushi*; Matsushita, Kentaro; Ezure, Toshiki; Tanaka, Masaaki
no journal, ,
In a sodium-cooled fast reactor, the inflow of entrained gas by a free surface vortex in the reactor vessel into the reactor core may cause reactivity disturbance. Therefore, a method to evaluate the gas entrainment (GE) volume flow rate is required in the design of fast reactors. In this study, as part of the investigation of the mechanism determining the GE volume flow rate, the numerical analysis targeting the free surface vortex in an experimental system in which the upper and lower cylindrical containers are connected by piping was performed, and the GE volume flow rate under various pressure conditions was evaluated. As the result, it was confirmed that the change in GE volume flow rate when the pressure difference between the upper and lower containers was changed was consistent between the experimental and analysis results, and that the GE volume flow rate could be evaluated by numerical analysis.
Matsushita, Kentaro; Ezure, Toshiki; Imai, Yasutomo*; Fujisaki, Tatsuya*; Tanaka, Masaaki
no journal, ,
In sodium-cooled fast reactors, the cover gas is entrained into the coolant due to the dimple vortices generated in the free surface in the upper plenum of the reactor vessel, and gas entrainment (GE) phenomenon may affect core behavior. It is necessary to develop evaluation methods of GE phenomenon. In this study, a GE evaluation model, PVL model (Pressure Vortex Line model) was constructed. The PVL model includes the identification of vortex center lines from the flow velocity distribution obtained by 3-D analysis, the calculation of the 3-D distribution of pressure decrease along the vortex center line and the evaluation of gas core length of vortex by comparing the pressure decrease and the hydrostatic pressure. The PVL model was applied to the analysis results of advective vortex experiments in a rectangular channel system to evaluate GE. As the result, it was confirmed that it was possible to judge the GE occurrence of advective vortices by the application of PVL model.