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Asahara, Makoto*; Iwasaki, Kodai*; Kamiya, Tomohiro; Mizuno, Kyohei*; Iwatsuki, Kazuma*; Miyasaka, Takeshi*
Konsoryu, 38(2), p.175 - 185, 2024/06
Breakup of a single droplet induced by a high-velocity gas flow behind a shock wave was observed with high spatio-temporal accuracy imaging, and the behavior of fragment formation was observed. In the high Weber number region corresponding to catastrophic breakup, the wavelength of the upstream interfacial wave of the droplet was larger than the critical wavelength of the Kelvin-Helmholtz instability (wavelength in the stability region), which was roughly consistent with the theoretical wavelength of the Rayleigh-Taylor instability. Therefore, the upstream interfacial wave of the droplet is generated by the development of small disturbances due to the Rayleigh-Taylor instability. The measured fragment diffusion widths were found to be independent of the Weber number.
Takeda, Tetsuaki*; Inagaki, Yoshiyuki; Aihara, Jun; Aoki, Takeshi; Fujiwara, Yusuke; Fukaya, Yuji; Goto, Minoru; Ho, H. Q.; Iigaki, Kazuhiko; Imai, Yoshiyuki; et al.
High Temperature Gas-Cooled Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.5, 464 Pages, 2021/02
As a general overview of the research and development of a High Temperature Gas-cooled Reactor (HTGR) in JAEA, this book describes the achievements by the High Temperature Engineering Test Reactor (HTTR) on the designs, key component technologies such as fuel, reactor internals, high temperature components, etc., and operational experience such as rise-to-power tests, high temperature operation at 950
C, safety demonstration tests, etc. In addition, based on the knowledge of the HTTR, the development of designs and component technologies such as high performance fuel, helium gas turbine and hydrogen production by IS process for commercial HTGRs are described. These results are very useful for the future development of HTGRs. This book is published as one of a series of technical books on fossil fuel and nuclear energy systems by the Power Energy Systems Division of the Japan Society of Mechanical Engineers.
Sasa, Toshinobu; Umeno, Makoto*; Mizubayashi, Hiroshi*; Mori, Keijiro*; Futakawa, Masatoshi; Saito, Shigeru; Kai, Tetsuya; Nakai, Kimikazu*; Zako, Akira*; Kasahara, Yoshiyuki*; et al.
JAERI-Tech 2005-021, 114 Pages, 2005/03
JAERI-Tech-2005-021.pdf:9.66MB
To perform the research and development for accelerator-driven system (ADS), Japan Atomic Energy Research Institute (JAERI) plans to build a Transmutation Experimental Facility under the JAERI-KEK joint J-PARC program. Transmutation Experimental Facility consists of two buildings, Transmutation Physics Experimental Facility to make reactor physics experiment with subcritical core, and ADS Target Test Facility for the preparation of irradiation database for various structural materials. In this report, purpose to build, experimental schedule, and design study of the ADS target test facility with drawer type spallation target are summarized.
Yokoyama, Kenji; Hosogai, Hiromi*; Chiba, Go; Kasahara, Naoto; Ishikawa, Makoto
JNC TN9400 2004-022, 162 Pages, 2004/04
JNC-TN9400-2004-022.pdf:13.47MB
In the fast reactor development, numerical simulation using analysis code plays an important role for complementing theory and experiment. In order to efficiently advance the research and development of fast reactors, JNC promotes the development of next generation simulation code (NGSC). In this report, research result by prototyping which carried out for the conceptual design of the NGSC is described. From the viewpoint of the cooperative research with CEA (Commissariat a l'Energie Atomique) in France, a trend survey on several platforms for numerical analysis and an applicability evaluation of CEA's SALOME platform for the NGSC were carried out. As a result of the evaluation, it is confirmed that SALOME had been satisfied the features of efficiency, openness, universality, expansibility and completeness that are required by the NGSC. In addition, it is confirmed that SALOME had the concept of the control layer required by the NGSC and would be one of the important candidates as a platform of the NGSC. In the field of the structure analysis, the prototype of the PARTS.NET code was reexamined from the viewpoint of class structure and input/output specification in order to improve the data processing efficiency and maintainability. In the field of the reactor physics analysis, a development test of a new code with C++ and a reuse test of an existing code written in Fortran was carried out in view of utilizing SALOME for the NGSC.
Yokoyama, Kenji; Hosogai, Hiromi*; Uto, Nariaki; Kasahara, Naoto; Ishikawa, Makoto
JNC TN9400 2003-021, 205 Pages, 2003/04
JNC-TN9400-2003-021.pdf:8.86MB
In the fast reactor development, numerical simulation using analytical codes plays an important role for complementing theory and experiment. It is necessary that the engineering models and analysis methods can be flexibly changed, because the phenomina to be investigated become more complicated due to the diversity of the needs for research. And, there are large problems in combining physical propaties and engineering models in many different fields. Aming to the realization of the next generation code system which can solve those problems, the authors adopted three methods, (1)Multi-language (SoftWIRE.NET, Visual Basic .NET and Fortran) (2)Fortran90 and (3)Python to make a prototype of the next generation code system. As this result, the followings were comfirmed. (1)It is possible to reuse a function of the existing codes written in Fortran as an object of the next generation code system by using visual Basic .NET. (2)The maintenanability of the existing code written by Fortran77 can be improved by using the new features of Fortran90. (3)The toolbox-type code system can be built by using Python.
Yokoyama, Kenji; Uto, Nariaki; kasahara, Naoto; ; Ishikawa, Makoto
Nihon Genshiryoku Gakkai 2003-Nen Aki No Taikai, 2(E64), 343 Pages, 2003/00
None
Yokoyama, Kenji; Hosogai, Hiromi*; Uto, Nariaki; Kasahara, Naoto; Nagura, Fuminori; ; ; Ishikawa, Makoto
JNC TN9420 2002-004, 309 Pages, 2002/11
JNC-TN9420-2002-004.pdf:11.4MB
In the fast reactor development, numerical simulation using analytical codes plays an important role for complementing theory and experiment. It is necessary that the engineering models and analysis methods can be flexibly changed, because the phenomina to be investigated become more complicated due to the diversity of the needs for research. And, there are large problems in combining physical propaties and engineering models in many different fields. In this study, the goal is to develop a flexible and general-purposive analysis system, in which the phisical propaties and engineering models are replesented as a programming languare or a diagams that are easily understandable for humans and executable for computers. The authors named this concept the Engineering Modeling Language(EML). This report describes the result of the investigation for latest computer technologies and software development techniques which seem to be usable for a realization of the analysis code system for nuclear engineering as an EML.
C at FCA, 1; Development of experimental device for Doppler reactivity worth measurement with small sample heated up to 1500COigawa, Hiroyuki; Okajima, Shigeaki; Mukaiyama, Takehiko; ; Hishida, Makoto; ; ; Kasahara, Y.*
JAERI-M 94-043, 46 Pages, 1994/03
no abstracts in English
Mizuno, Makoto; Hanada, Masaya; Inoue, Takashi; Ohara, Yoshihiro; Okumura, Yoshikazu; Tanaka, Shigeru; Watanabe, Kazuhiro; Asahara, Masaharu*; ; ; et al.
Fusion Engineering and Design, 23, p.49 - 55, 1993/00
Times Cited Count：3 Percentile：37.41(Nuclear Science & Technology)no abstracts in English
Ueda, Hayate*; Kamiya, Tomohiro; Asahara, Makoto*
no journal, ,
In a steam explosion caused by the penetration of molten metal into water, shock waves and pressure waves with rapid pressure rises are generated, leading to damage in the surrounding area. The collapse of the vapor film is expected to generate pressure waves from multiple molten metal fragments and amplify them. These pressure wave propagation mechanisms are complex, and clarifying the mechanism of initial pressure wave generation from a single droplet is an important task for accurate prediction and evaluation. Therefore, this study focuses on the steam explosion phenomenon involving a single molten metal droplet. In this presentation, we report the results of visualizing the behavior of the steam explosion generated from a single molten metal droplet and measuring the associated pressure waves.
Ueda, Hayate*; Asahara, Makoto*; Kitagawa, Kazutaka*; Miyasaka, Takeshi*; Kamiya, Tomohiro
no journal, ,
A vapor explosion is a unique explosive phenomenon that occurs due to the rapid interaction between molten material and coolant. It is a concern during severe accidents in nuclear reactors and can also contribute to the escalation of damage during submarine volcanic eruptions. The strong pressure waves generated in the initial stages are believed to propagate while affecting the surrounding molten material; however, their propagation characteristics are not yet fully understood. In this study, experiments were conducted in which a single molten metal droplet was dropped into water, and the pressure waves generated by spontaneous vapor explosion were measured using pressure sensors and a high-speed camera.
Kamiya, Tomohiro; Ueda, Hayate*; Asahara, Makoto*
no journal, ,
In a vapor explosion, molten material is dispersed in the water, and the pressure waves interact with the molten material and with other pressure waves, eventually forming the final pressure wave. Because such pressure wave propagation processes are complex, a detailed understanding through simulation is expected. The pressure waves originate from the rapid pressure increase caused by the abrupt phase change. Additionally, a vapor explosion involves a multiphase flow in which water, vapor, and molten material coexist, and it is necessary to handle the interfaces accurately. We modeled the pressure increase due to phase change and incorporated it into an interface capturing scheme suitable for detailed analysis. We will report the results of a single droplet vapor explosion simulation.
Ueda, Hayate*; Asahara, Makoto*; Kamiya, Tomohiro
no journal, ,
Vapor explosions occur when the thermal energy of a molten metal droplet immersed in water is rapidly converted into mechanical energy. The metal droplet breakup promotes this conversion and thus has a significant influence on explosion behavior. In this study, optical visualization and pressure measurements were performed in vapor explosion experiments with a single droplet. The results confirmed the generation of pressure waves associated with the breakup, and data contributing to the development of vapor explosion models were obtained.
Kamiya, Tomohiro; Asahara, Makoto*
no journal, ,
A vapor explosion has been considered to consist of a coarse mixing phase in which molten fuel falls into the water and is disintegrated and an explosion phase in which an explosion with a shock wave through the molten fuel droplets occurs. The target of safety assessment is the shock wave propagating through molten droplets and the shock-induced flow of water, vapor, and molten fluid mixture. We aim to clarify the strength of the shock wave and its formation and propagation mechanism by conducting experiments and numerical analysis of the vapor explosion of a droplet line system, a simplified version of a multiple droplet system. The background, objectives, and contents of the study will be reported.
