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Watanabe, Seiya*; Kawahara, Jun*; Aoki, Takayuki*; Sugihara, Kenta; Takase, Shinsuke*; Moriguchi, Shuji*; Hashimoto, Hirotada*
Engineering Applications of Computational Fluid Mechanics, 17(1), p.2211143_1 - 2211143_23, 2023/00
Times Cited Count：1 Percentile：61.52(Engineering, Multidisciplinary)In tsunami inundations or slope disasters of heavy rain, a lot of floating debris or driftwood logs are included in the flows. The damage to structures from solid body impacts is more severe than the damage from the water pressure. In order to study free-surface flows that include floating debris, developing a high-accurate simulation code of free-surface flows with high performance for large-scale computations is desired. We propose the single-phase free-surface flow model based on the cumulant lattice Boltzmann method coupled with a particle-based rigid body simulation. The discrete element method calculates the contact interaction between solids. An octree-based AMR (Adaptive Mesh Refinement) method is introduced to improve computational accuracy and time-to-solution. High-resolution grids are assigned near the free surfaces and solid boundaries. We conducted two kinds of tsunami flow experiments in the 15 and 70 m water tanks at Hachinohe Institute of Technology and Kobe University to validate the accuracy of the proposed model. The simulation results have shown good agreement with the experiments for the drifting speed, the number of trapped wood pieces, and the stacked angles.
Torikawa, Tomoaki*; Odaira, Naoya*; Ito, Daisuke*; Ito, Kei*; Saito, Yasushi*; Matsushita, Kentaro; Ezure, Toshiki; Tanaka, Masaaki
Konsoryu, 36(1), p.63 - 69, 2022/03
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, entrained gas flow rate a simple gas entrainment experiment is conducted with focusing on effect of pressure difference between upper and lower tanks. Pressure difference between upper and lower tanks are controlled by changing gas pressure in lower tank. As a result, it is confirmed that the entrained gas flow rate increases with increasing pressure difference between upper and lower tanks. By visualization of swirling annular flow in suction pipe, it is also observed that pressure drop in suction pipe increases with increase in entrained gas flow rate, which implies that entrained gas flow rate can be predicted by evaluation model based on pressure drop in swirling annular flow region.
Wang, Z.; Duan, G.*; Koshizuka, Seiichi*; Yamaji, Akifumi*
Nuclear Power Plant Design and Analysis Codes, p.439 - 461, 2021/00
2 mMatsubara, Akihiro; Fujita, Natsuko; Kimura, Kenji
Proceedings of the 8th East Asia Accelerator Mass Spectrometry Symposium and the 22nd Japan Accelerator Mass Spectrometry symposium (EA-AMS 8 & JAMS-22), p.57 - 59, 2020/00
no abstracts in English
Ota, Masakazu; Kwamena, N.-O. A.*; Mihok, S.*; Korolevych, V.*
Journal of Environmental Radioactivity, 178-179, p.212 - 231, 2017/11
Times Cited Count：14 Percentile：43.57(Environmental Sciences)Environmental transfer models assume that organically-bound tritium (OBT) is formed directly from tissue-free water tritium (TFWT) in environmental compartments. Nevertheless, studies in the literature have shown that measured OBT/TFWT ratios are variable. The importance of soil-to-leaf HTO transfer pathway in controlling the leaf tritium dynamics is not well understood. A model inter-comparison of two tritium transfer models (CTEM-CLASS-TT and SOLVEG-II) was carried out with measured environmental samples from an experimental garden plot set up next to a tritium-processing facility. The garden plot received one of three different irrigation treatments - no external irrigation, irrigation with low tritium water and irrigation with high tritium water. The contrast between the results obtained with the different irrigation treatments provided insights into the impact of soil-to-leaf HTO transfer on the leaf tritium dynamics. Concentrations of TFWT and OBT in the garden plots that were not irrigated or irrigated with low tritium water were variable, responding to the arrival of the HTO-plume from the tritium-processing facility. In contrast, for the plants irrigated with high tritium water, the TFWT concentration remained elevated due to a continuous source of high HTO in the soil. Calculated concentrations of OBT in the leaves showed an initial increase followed by quasi-equilibration with the TFWT concentration. In this quasi-equilibrium state, concentrations of OBT remained elevated and unchanged despite the arrivals of the plume. These results from the model inter-comparison demonstrate that soil-to-leaf HTO transfer significantly affects OBT/TFWT ratio in the leaf regardless of the atmospheric HTO concentration, only if there is elevated HTO concentrations in the soil. The results of this work indicate that assessment models should be refined to consider the importance of soil-to-leaf HTO transfer to ensure that dose estimates are accurate and conservative.
Ito, Kei; Ohno, Shuji; Koizumi, Yasuo*; Kawamura, Takumi*
Proceedings of 10th International Topical Meeting on Nuclear Thermal Hydraulics, Operation and Safety (NUTHOS-10) (USB Flash Drive), 10 Pages, 2014/12
Shibamoto, Yasuteru
JAERI-Research 2005-016, 127 Pages, 2005/08
JAERI-Research-2005-016.pdf:4.54MB
no abstracts in English
Nakamura, Hiroshi; Ida, Mizuho*; Nakamura, Hiroo; Nakamura, Hideo; Ezato, Koichiro; Akiba, Masato
JAERI-Research 2000-068, 30 Pages, 2001/02
JAERI-Research-2000-068.pdf:3.88MB
no abstracts in English
Ito, Kazuhiro*; Tsuji, Yoshiyuki*; Nakamura, Hideo; Kukita, Yutaka*
Fusion Technology, 37(1), p.74 - 88, 2000/01
no abstracts in English
*; ; Nakamura, Hideo
JAERI-Research 98-022, 46 Pages, 1998/03
JAERI-Research-98-022.pdf:1.92MB
no abstracts in English
Kunugi, Tomoaki
Nihon Kikai Gakkai Rombunshu, B, 63(609), p.88 - 96, 1997/05
no abstracts in English
; ; *; ;
Nihon Genshiryoku Gakkai-Shi, 27(3), p.250 - 261, 1985/00
Times Cited Count：13 Percentile：81.94(Nuclear Science & Technology)no abstracts in English
YRadiochem.Radioanal.Lett., 27(1), p.21 - 25, 1976/01
no abstracts in English
Ote, Naosuke*; Koizumi, Yasuo*; Kamide, Hideki; Ohno, Shuji; Ito, Kei
no journal, ,
A sodium-cooled fast breeder reactor is now at the development stage in Japan. One concern for safety is cover gas entrainment into the sodium coolant. The gas entrainment rate into liquid by the vortex formed on the free surface was examined experimentally. Liquid flowed into a cylindrical vessel from a wall tangentially. Swirl flow was formed in the vessel, and then liquid drained from the bottom outlet of the vessel. A hollow vortex was formed on the free surface in the test vessel. The air was entrained under the free surface of the vortex and carried away from the bottom of the vessel. The flow state of the gas entertainment was visually observed by using a high speed video camera. The gas entrainment rate into liquid was measured. In the previous study, test fluid was water. Kerosene and 20 cSt silicone oil were newly introduced as the test fluid to examine the effect of the physical properties on the gas entertainment phenomena.
Ohashi, Kunihide*; Onodera, Naoyuki
no journal, ,
The applicability of shared memory type computing with Xeon Phi Knights Landing processor is examined with the flow solver which is dedicated to the flow computation around a ship hull. The computations at the high Reynolds number with the one- or two-equation turbulence models and the free surface model, additionally, the over-set grid method are selected as the test cases. The processing speeds of the Xeon Broadwell and the Skylake processors show better results than the speed of the Xeon Phi processors. The speed up ratio is smoothly increasing until the maximum number of the core with using the Xeon Phi processor.
Sago, Hiromi*; Yamamoto, Tomohiko; Miyazaki, Masashi; Tanaka, Masaaki; Yokoi, Shinobu*; Yamane, Yuma*; Nishiwaki, Yoshinori*; Morita, Hideyuki*; Iwasaki, Akihisa*; Ikesue, Shunichi*; et al.
no journal, ,
The design basis ground motions have been revised to improve the seismic resistance of nuclear power plants. The reduction of seismic forces not only horizontally but also vertically has required more critical than in the past to ensure the seismic resistance of components. Notably, the design of a Sodium-Cooled Fast Reactor will require reducing the seismic forces applied to the components because of the components with thin wall thickness. To overcome this problem, the authors plan to introduce a seismic isolation system. When the sloshing wave height is small, it can be approximated with a linear vibration model. However, when the sloshing wave height increases and the sloshing becomes nonlinear, it is necessary to evaluate the wave height using other methods such as numerical analysis. Although the evaluation of nonlinear sloshing wave height is important, there are few examples which quantitatively evaluate the wave height of nonlinear sloshing. This paper reports the results of the sloshing water test carried out to obtain test data for the construction of the evaluation method and the results of the reproduction analysis carried out using the VOF method.
Morita, Hideyuki*; Yamamoto, Tomohiko; Miyazaki, Masashi; Tanaka, Masaaki; Yokoi, Shinobu*; Sago, Hiromi*; Ikesue, Shunichi*
no journal, ,
The design basis ground motions have been revised to improve the seismic resistance of nuclear power plants. The reduction of seismic forces not only horizontally but also vertically has required more critical than in the past to ensure the seismic resistance of components. Notably, the design of a Sodium-Cooled Fast Reactor will require reducing the seismic forces applied to the components because of the components with thin wall thickness. To overcome this problem, the authors plan to introduce a seismic isolation system. When the sloshing wave height is small, it can be approximated with a linear vibration model. However, when the sloshing wave height increases and the sloshing becomes nonlinear, itis necessary to evaluate the wave height using other methods such as numerical analysis. Although the evaluation of nonlinear sloshing wave height is important, there are few examples which quantitatively evaluate the wave height of nonlinear sloshing. This paper reports on the study result of the predictive evaluation method for nonlinear sloshing wave height and impact load acting on the flat roof applied to cylindrical tanks.
