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Journal Articles

Development of evaluation method for in-place cooling of residual core materials in core disruptive accidents of SFRs

Imaizumi, Yuya; Aoyagi, Mitsuhiro; Kamiyama, Kenji; Matsuba, Kenichi; Ganovichev, D. A.*; Baklanov, V. V.*

Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 11 Pages, 2019/05

The cooling of the residual core materials after the fuel discharge from the core in the accident of SFRs can significantly affect the distribution fraction of the core materials, which is an important factor for the in-vessel retention (IVR). For the evaluation of the cooling of the residual core materials which is called ``in-place cooling'', behavior in a SFR core was analyzed preliminary by SIMMER-III. Based on the analysis result, method of phenomena identification and ranking table (PIRT) was applied. Fundamental experiment focusing on three thermal-hydraulic phenomena those were extracted by PIRT was considered in order to investigate them and utilize it for validation of the SIMMER-III. To achieve continuous oscillation of sodium level which can occur in the phase of in-place cooling of SFRs, analytical survey was conducted by SIMMER-III. As a result of that, the effects of experimental conditions on the oscillation amplitude and the duration time were clarified quantitatively, which are necessary to determine the specific experimental conditions.

Journal Articles

Droplet generation during liquid jet impingement onto a horizontal plate

Zhan, Y.*; Oya, Naoki*; Enoki, Koji*; Okawa, Tomio*; Aoyagi, Mitsuhiro; Takata, Takashi

Experimental Thermal and Fluid Science, 98, p.86 - 94, 2018/11

 Percentile:100(Thermodynamics)

Journal Articles

Multi-dimensional numerical investigation of sodium spray combustion; Benchmark analysis of SNL T3 experiment

Sonehara, Masateru; Aoyagi, Mitsuhiro; Uchibori, Akihiro; Takata, Takashi; Ohshima, Hiroyuki; Clark, A. J.*; Denman, M. R.*

Proceedings of 11th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-11) (Internet), 5 Pages, 2018/11

no abstracts in English

Journal Articles

Numerical modeling of radiation heat transfer under sodium spray combustion in sodium-cooled fast reactors

Aoyagi, Mitsuhiro; Takata, Takashi; Ohno, Shuji; Uno, Masayoshi*

Proceedings of 12th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics, Operation and Safety (NUTHOS-12) (USB Flash Drive), 10 Pages, 2018/10

Heat radiation is one of dominant heat transfer process during a sodium fire event which is a concern in sodium-cooled fast reactor plants. This study aims to model radiation heat transfer from combusting droplets. Radiation energy transport on the combustion flame surface around a sodium droplet is formulated considering emission, absorption and scattering through a similar approach to the formulation of the wall boundary condition. The improved model is tested trough a simple verification analysis and a benchmark analysis on an upward sodium spray combustion experiment. As the result, overestimation of atmospheric temperature and pressure is mitigated by the improved model due to increase in heat transfer to structure.

Journal Articles

A Study on splashing during liquid jet impingement onto a horizontal plate

Kuwata, Yusuke*; Zhan, Y.*; Enoki, Koji*; Okawa, Tomio*; Aoyagi, Mitsuhiro; Takata, Takashi

Proceedings of 12th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics, Operation and Safety (NUTHOS-12) (USB Flash Drive), 10 Pages, 2018/10

This study aims improvement of safety analysis for sodium fire accidents in sodium-cooled fast reactors. In the experiment, effect of viscosity on liquid jet impact on solid surface was studied.

Journal Articles

Estimation of porosity and void fraction profiles in a packed bed of spheres using X-ray radiography

Ito, Daisuke*; Ito, Kei*; Saito, Yasushi*; Aoyagi, Mitsuhiro; Matsuba, Kenichi; Kamiyama, Kenji

Nuclear Engineering and Design, 334, p.90 - 95, 2018/08

 Percentile:100(Nuclear Science & Technology)

Two-phase flow through porous media must be well understood to develop a severe accident analysis code not only for light water reactor but also sodium-cooled fast reactor. When a core disruptive accident occurs in sodium-cooled fast reactor, the fuel inside the core become melted and interacts with the coolant. As a result, gas-liquid two-phase flow will be formed in the debris bed, which may have porous nature depending on the cooling process. In such condition, the local porosity and its distribution are very important to characterize two-phase flow field in the porous media. In this study, X-ray radiography was applied to measure the local porosity in the packed bed of spheres. The radial profiles were estimated from the chordal profiles measured by the X-ray method and compared with the previous porosity model. In addition, the void fraction radial profiles were also obtained in air-water two-phase flow.

Journal Articles

Improvement of a physical model for blockage formation of solid-liquid mixture flow with freezing for core safety evaluation of SFRs

Aoyagi, Mitsuhiro; Kamiyama, Kenji; Tobita, Yoshiharu

Journal of Nuclear Science and Technology, 55(5), p.530 - 538, 2018/05

 Times Cited Count:1 Percentile:38.14(Nuclear Science & Technology)

Journal Articles

Application of multi-dimensional sodium fire analysis code AQUA-SF to severe accident; Benchmark analysis of upward spray combustion experiment

Aoyagi, Mitsuhiro; Takata, Takashi; Ohno, Shuji; Uno, Masayoshi*

Nippon Kikai Gakkai Rombunshu (Internet), 84(859), p.17-00374_1 - 17-00374_13, 2018/03

no abstracts in English

Journal Articles

Two-phase flow measurements in a simulated debris bed

Ito, Daisuke*; Rivera, M. N.*; Saito, Yasushi*; Aoyagi, Mitsuhiro; Kamiyama, Kenji; Suzuki, Toru*

Proceedings of 17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17) (USB Flash Drive), 10 Pages, 2017/09

Journal Articles

Measurements of two-phase pressure drop in a simulated debris bed

Nava, M.*; Ito, Daisuke*; Saito, Yasushi*; Aoyagi, Mitsuhiro; Kamiyama, Kenji; Suzuki, Toru*

Proceedings of 25th International Conference on Nuclear Engineering (ICONE-25) (CD-ROM), 5 Pages, 2017/07

Journal Articles

Splash during liquid jet impingement onto a horizontal plate

Zhan, Y.*; Oya, Naoki*; Enoki, Koji*; Okawa, Tomio*; Ohno, Shuji; Aoyagi, Mitsuhiro; Takata, Takashi

Proceedings of 25th International Conference on Nuclear Engineering (ICONE-25) (CD-ROM), 6 Pages, 2017/07

It is important to set the amount of sodium droplet mechanistically for appropriate numerical evaluations of sodium leak and fire behavior in a sodium-cooled fast reactor plant. In the present work, fundamental experiments are performed to measure the splash ratio during the vertical water jet impact onto a horizontal wall. It is shown that the splash ratio can be correlated well as a function of the impact Weber number and dimensionless impact frequency.

Journal Articles

Characteristics of pressure drop and void fraction in a simulated debris bed

Ito, Daisuke*; Nava, M.*; Saito, Yasushi*; Aoyagi, Mitsuhiro; Kamiyama, Kenji; Suzuki, Toru*

Proceedings of 2017 Japan-US Seminar on Two-Phase Flow Dynamics (JUS 2017), 4 Pages, 2017/06

Journal Articles

Identification of important phenomena under sodium fire accidents based on PIRT process

Aoyagi, Mitsuhiro; Uchibori, Akihiro; Kikuchi, Shin; Takata, Takashi; Ohno, Shuji; Ohshima, Hiroyuki

Proceedings of International Conference on Fast Reactors and Related Fuel Cycles; Next Generation Nuclear Systems for Sustainable Development (FR-17) (USB Flash Drive), 10 Pages, 2017/06

The present PIRT process is aimed to identify key phenomena involved in sodium fire accidents that involve complex phenomena in sodium-cooled fast reactor plants. In this PIRT process, the figures of merit (FOMs) are specified through factor analysis. Associated phenomena are identified through the element- and sequence-based phenomena analyses. Importance of each associated phenomenon is evaluated by considering the sequence-based analysis of associated phenomena correlated with the FOMs. Then, we complete the ranking table through the factor and phenomenon analyses. An assessment matrix of important phenomena and experiments is completed finally for model validation.

Journal Articles

Production of droplets during liquid jet impingement onto a flat plate

Yi, Z.*; Oya, Naoki*; Enoki, Koji*; Okawa, Tomio*; Ohno, Shuji; Aoyagi, Mitsuhiro; Takata, Takashi

Proceedings of 10th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-10) (USB Flash Drive), 7 Pages, 2016/11

It is important to set the amount of sodium droplet mechanistically for appropriate numerical evaluations of sodium leak and fire behavior in a sodium-cooled fast reactor plant. In the present work, fundamental experiments were performed to measure the splash ratio during the vertical water jet impact onto a horizontal wall. It was shown that the splash ratio can be correlated well as a function of the impact Weber number, the Strouhal number and the Ohnesorge number of the droplets impinging the liquid film.

Journal Articles

Identification of important phenomena under sodium fire accidents based on PIRT process with factor analysis in sodium-cooled fast reactor

Aoyagi, Mitsuhiro; Uchibori, Akihiro; Kikuchi, Shin; Takata, Takashi; Ohno, Shuji; Ohshima, Hiroyuki

Proceedings of 10th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-10) (USB Flash Drive), 10 Pages, 2016/11

The present PIRT process was aimed to identify key phenomena involved in sodium fire accidents that involve complex phenomena in sodium-cooled fast reactor plants. In this PIRT process, the figures of merit (FOMs) were specified through factor analysis. Associated phenomena were identified through the element- and sequence-based phenomena analyses. Importance of each associated phenomenon was evaluated by considering the sequence-based analysis of associated phenomena correlated with the FOMs. Then, we complete the ranking table through the factor and phenomenon analyses.

Journal Articles

Experimental study on splashing during liquid jet impingement onto a liquid film

Yi, Z.*; Oya, Naoki*; Enoki, Koji*; Okawa, Tomio*; Ohno, Shuji; Aoyagi, Mitsuhiro

Proceedings of 24th International Conference on Nuclear Engineering (ICONE-24) (DVD-ROM), 7 Pages, 2016/06

It is important to set the amount of sodium droplet mechanistically for appropriate numerical evaluations of sodium leak and fire behavior in a sodium-cooled fast reactor plant. In the present work, fundamental experiments were performed to measure the splash ratio during the vertical water jet impact onto a horizontal wall. It was shown that the splash ratio can be correlated well as a function of the impact Weber number and the Strouhal number of the droplets impinging the liquid film.

Journal Articles

Validation and improvement of a numerical model for freezing and blockage formation of solid-liquid flow of molten fuel in the core disruptive accident of FBR

Aoyagi, Mitsuhiro; Kamiyama, Kenji; Tobita, Yoshiharu; Suzuki, Toru

Proceedings of 10th International Topical Meeting on Nuclear Thermal Hydraulics, Operation and Safety (NUTHOS-10) (USB Flash Drive), 14 Pages, 2014/12

A numerical model for freezing and blockage formation of solid-liquid flow in the SIMMER code was validated in order to improve the accuracy in evaluating fuel discharge behavior in the core disruptive accident of FBR. The THEFIS experiment which investigated fuel discharge behavior was chosen as reference data in this study. The numerical conditions were set according to the experimental system. Although the experimental result was well simulated by using the existing numerical model of SIMMER, the melt flow was suppressed excessively in some cases. Overestimation of flow resistance by the solid particles in the numerical model was discovered though the comparison between the numerical model and the physical phenomenon in the experiment. The numerical model caused the excessive melt flow suppression. Therefore, we improved the numerical model to adapt to the actual phenomenon. Then, it was confirmed the improved numerical model brought more appropriate numerical results.

Journal Articles

Numerical study of the MHD flow characteristics in a three-surface-multi-layered channel with different inlet conditions

Aoyagi, Mitsuhiro; Ito, Satoshi*; Hashizume, Hidetoshi*

Fusion Engineering and Design, 89(7-8), p.1227 - 1231, 2014/10

 Times Cited Count:1 Percentile:85.45(Nuclear Science & Technology)

A 3D MHD flow simulation was conducted to clarify the effects of the inlet flow condition on the result of the validation experiment carried out previously and on the design window of the first wall using a three-surface-multi-layered channel. MHD pressure drop was influenced by the inlet condition largely. The numerical model with turbulent velocity profile showed qualitatively good agreement with the experimental result. The first wall temperature distribution obtained by the 3D simulation corresponded well the one by the 2D simulation assuming fully developed flow. This meant complicated three-dimensional inlet flow condition generated in the L-shape elbow would not affects the existing design window.

Oral presentation

Validation of a numerical model of solid-liquid flow for freezing and blockage formation of molten fuel in the core disruptive accident of FBR

Aoyagi, Mitsuhiro; Kamiyama, Kenji; Tobita, Yoshiharu; Suzuki, Toru

no journal, , 

A numerical model for solid-liquid flow for freezing and blockage formation in the SIMMER code was validated in order to improve the accuracy in evaluating fuel discharge behavior in the core disruptive accident of FBR. The THEFIS experiment which investigated fuel discharge behavior was chosen as reference data in this study. The numerical conditions were set according to the experimental system. Although the experimental result was well simulated by using the existing numerical model of SIMMER, the melt flow was suppressed excessively in some cases. Overestimation of flow resistance by the solid particles in the numerical model was discovered though the comparison between the numerical model and the physical phenomenon in the experiment. The numerical model caused the excessive melt flow suppression. Therefore, we improved the numerical model to adapt to the actual phenomenon. Then, it was confirmed the improved numerical model brought more appropriate numerical results.

Oral presentation

Development of evaluation methodology for in-place cooling in disrupted core of sodium-cooled fast reactor; Prediction of dominant phenomena based on numerical analyses

Aoyagi, Mitsuhiro; Kamiyama, Kenji; Matsuba, Kenichi; Tobita, Yoshiharu; Suzuki, Toru

no journal, , 

no abstracts in English

49 (Records 1-20 displayed on this page)