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Matsushita, Kentaro; Ezure, Toshiki; Imai, Yasutomo*; Fujisaki, Tatsuya*; Tanaka, Masaaki
Proceedings of 29th International Conference on Nuclear Engineering (ICONE 29) (Internet), 8 Pages, 2022/08
Development of evaluation method for cover gas entrainment (GE) by vortices generated at free surface in upper plenum of sodium-cooled fast reactor (SFR) is required. GE evaluation tool, named StreamViewer, based on method using numerical results of three-dimensional computational fluid dynamics analysis for loop-type SFRs has been developed. In this study, modification of evaluation method of StreamViewer to rationalize conservativeness in evaluation results was examined by identifying vortex center lines and calculating three-dimensional distribution of pressure decrease along vortex center lines. The applicability of modified method was checked using water experimental result in rectangular open channel where unsteady vortices are generated. As the result, it was indicated that evaluation results on gas core depth which were excessive in current method were improved in modified method, and it is confirmed that modified method may discriminate onset of GE with appropriate criteria.
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.
Sekine, Yurina; Kobayashi, Riki*; Chi, S.*; Fernandez-Baca, J. A.*; Suzuya, Kentaro; Fujisaki, Fumika*; Ikeda, Kazutaka*; Otomo, Toshiya*; Fukazawa, Tomoko*; Yamauchi, Hiroki; et al.
JPS Conference Proceedings (Internet), 8, p.033009_1 - 033009_6, 2015/09
Neutron diffraction profiles of low-D
O-content poly-N,N,-dimethylacrylamide (PDMAA) hydrogels were measured from 100 to 300 K to investigate the structure and properties of water in hydrogels. A broad diffraction observed at temperatures lower than 220 K indicates the existence of amorphous ice in the hydrogels at low temperatures. During the heating process, diffraction peaks from ice crystals appear in the profiles. These peaks indicate that cubic ice and hexagonal ice exist at T 
220 K. We refined the structure parameters of these ices in the hydrogel, which indicate the existence of low-density ice in the hydrogel.
Tc-MDP using Tc separated from 
Mo produced by 
Mo(
,2)MoNagai, Yasuki; Hatsukawa, Yuichi; Kin, Tadahiro; Hashimoto, Kazuyuki; Motoishi, Shoji; Konno, Chikara; Ochiai, Kentaro; Takakura, Kosuke; Sato, Yuichi*; Kawauchi, Yukimasa*; et al.
Journal of the Physical Society of Japan, 80(8), p.083201_1 - 083201_4, 2011/08
Times Cited Count：15 Percentile：65.33(Physics, Multidisciplinary)We have for the first time succeeded to separate Tc from a Mo oxide sample irradiated by accelerator neutrons, and to formulate Tc-methylene diphosphonate (Tc-MDP). Mo, the mother nuclide of Tc, was produced by the Mo(,2)Mo reaction using about 14 MeV neutrons provided at the Fusion Neutronics Source of Japan Atomic Energy Agency. The Tc was separated from Mo by the sublimation method, and its radionuclide purity was confirmed to be higher than 99.99%. The labeling efficiency of Tc-MDP was shown to be higher than 99%. These values exceed the United States Pharmacopeia requirements for a fission product, Mo. Consequently, a Tc radiopharmaceutical preparation formed by using the mentioned Mo can be a promising substitute for the fission product Mo. A longstanding problem to ensure a reliable and constant supply of Mo in Japan can be partially mitigated.
Yokobori, Shinichi*; Yang, Y.*; Fujisaki, Kenta*; Kawaguchi, Yuko*; Kobayashi, Kensei*; Hashimoto, Hirofumi*; Kawai, Hideyuki*; Mita, Hajime*; Narumi, Issei; Okudaira, Kyoko*; et al.
no journal, ,
no abstracts in English
Yokobori, Shinichi*; Yang, Y.*; Fujisaki, Kenta*; Kawaguchi, Yuko*; Hashimoto, Hirofumi*; Yamashita, Masamichi*; Yano, Hajime*; Okudaira, Kyoko*; Yoshimura, Yoshitaka*; Narumi, Issei; et al.
no journal, ,
no abstracts in English
Yokobori, Shinichi*; Fujisaki, Kenta*; Kawaguchi, Yuko*; Yang, Y.*; Fushimi, Hidehiko*; Hashimoto, Hirofumi*; Yamashita, Masamichi*; Yano, Hajime*; Okudaira, Kyoko*; Hayashi, Nobuhiro*; et al.
no journal, ,
no abstracts in English
Yokobori, Shinichi*; Yang, Y.*; Sugino, Tomohiro*; Kawaguchi, Yuko*; Itahashi, Shiho*; Fujisaki, Kenta*; Fushimi, Hidehiko*; Hasegawa, Sunao*; Hashimoto, Hirofumi*; Hayashi, Nobuhiro*; et al.
no journal, ,
Suzuya, Kentaro; Oshita, Hidetoshi*; Otomo, Toshiya*; Ikeda, Kazutaka*; Seya, Tomohiro*; Kaneko, Naokatsu*; Fujisaki, Fumika*
no journal, ,
NOVA has almost 900 3-helium gas detectors for neutron diffraction measurements. Two Gas Electron Multiplier (GEMs) are installed as an incident-neutron and a transmission beam monitors. The performance of NOVA has been confirmed by several samples: structural analysis of crystalline and amorphous samples are demonstrated, the instrument background is low enough to measure S(Q) with the order of several ten mg for an hour. Typical S(Q) of silica glass (cylindrical rod, 20 mm long, and 7 mm diameter) is obtained up to 15 (1/
) for 1 sec and up to 35 (1/) for 20 sec. These results show that NOVA is a powerful instrument for in situ dynamic investigation of rapid structural transformation in supercooled liquids and in hydrogen storage materials. Some of recent results of disordered materials on NOVA will be presented.
by in-situ neutron diffraction measurementSuzuya, Kentaro; Fujisaki, Fumika*; Ikeda, Kazutaka*; Oshita, Hidetoshi*; Otomo, Toshiya*
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.
Matsushita, Kentaro; Ezure, Toshiki; Fujisaki, Tatsuya*; Imai, Yasutomo*; Tanaka, Masaaki
no journal, ,
Development of evaluation method for cover gas entrainment (GE) by vortices generated at free surface in upper plenum of sodium-cooled fast reactor (SFR) is required. An evaluation method by predicting vortices from flow velocity distribution obtained by 3D CFD analysis is developed, and partial refinement of analysis mesh from the viewpoint of improving efficiency of 3D CFD analysis is examined. In this study, a method of predicting vortex radius that can occur in a system by machine learning and using the predicted value as a reference value for analysis mesh before applying refinement (initial mesh). CFD analysis was performed for cylinder column system where wake vortex occurs by changing parameters such as cylinder diameter and inlet flow velocity, and supervised learning was performed using the obtained variables and vortex radius was predicted. As a result, it was obtained that initial mesh size can be efficiently determined by using the predicted vortex radius as a reference.
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.
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.
