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Okawa, Tomio*; Mori, Shoji*; Liu, W.*; Ose, Yasuo*; Yoshida, Hiroyuki; Ono, Ayako
Nihon Genshiryoku Gakkai-Shi ATOMO
, 63(12), p.820 - 824, 2021/12
The evaluation method of the critical heat flux based on the mechanism is needed for the efficient design and development of fuel in reactors and the appropriate safety evaluation. In this paper, the current researches relating to the mechanism of the critical heat flux are reviewed, and the issue to be considered in the future are discussed.
Ono, Ayako; Yamashita, Susumu; Suzuki, Takayuki*; Yoshida, Hiroyuki
Proceedings of 18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18) (USB Flash Drive), p.666 - 677, 2019/08
An evaluation methodology of critical heat fluxes (CHFs) based on a mechanism for fuel assemblies in light water reactors (LWRs) is needed in order to design and evaluate the safety for the fuel assemblies in LWRs. In our study, the numerical simulation with surface-tracking will be applied for the two-phase flow in fuel assemblies in order to obtain the detail data relating to the size and velocity of bubbles in the subchannel, which is needed to predict the CHF based on the mechanism. In this study, the numerical simulation of two-phase flow in 4
4 bundle was implemented by using JUPITER in order to establish the evaluation method of the size and velocity of bubbles by the numerical simulation, which is the multi-physics simulation code and enable to track the gas-liquid surface. The simulation results are validated by the curve of flow regime for air-water under the adiabatic condition. The bubble and velocity of bubbles obtained by simulation results are analyzed.
Ogawa, Masuro*
JAEA-Technology 2019-010, 22 Pages, 2019/07
JAEA-Technology-2019-010.pdf:1.5MB
Transition phenomena from laminar to turbulent flow are roughly classified into three categories. Circular pipe flow of the third category is linearly stable against any small disturbance, despite that flow actually transitions and transitional flow exhibits intermittency. These are among major challenges that are yet to be resolved in fluid dynamics. Thus, author proposes hypothesis as follows; "Flow in a circular pipe transitions from laminar flow because of vortices released from separation bubble forming in vicinity of inlet of pipe, and transitional flow becomes intermittent because vortex-shedding is intermittent." Present hypothesis can easily explain why linear stability theory has not been able to predict transition in circular pipe flow, why circular pipe flow actually transitions, why transitional flow actually exhibits intermittency even due to small disturbance, and why numerical analysis has not been able to predict intermittency of transitional flow in circular pipe.
Liu, W.; Podowski, M. Z.*
Nihon Kikai Gakkai Netsu Kogaku Konfarensu 2015 Koen Rombunshu (CD-ROM), 2 Pages, 2015/10
This paper gives prediction to the transient heat transfer at Departure of Nucleate Boiling (DNB) point for subcooled flow boiling. The prediction is carried out by solving the heat conduction equations in cylindrical coordinates with convective boundary condition, which changes with the change of the heat transfer mode on the heated surface. DNB is assumed to happen at the complete dryout of liquid sublayer trapped between the heated wall and an elongated vapor clot, during the passing time of the vapor clot. Important parameters including initial thickness of the liquid sublayer, vapor clot length, vapor clot velocity and void fraction etc., are calculated from the Liu - Nariai model. The initial heater surface temperature is derived from the Jens-Lottes correlation. The transient changes of liquid sublayer thickness, surface temperature at DNB are reported. No obvious temperature jumping is observed at DNB. To predict temperate excursion at Critical Heat Flux (CHF), more simulations to the transient boiling and film boiling processes are needed.
Kikuchi, Kenji; Takeda, Yasushi*; Obayashi, Hiroo*; Tezuka, Masao*; Sato, Hiroshi
Journal of Nuclear Materials, 356(1-3), p.273 - 279, 2006/09
Times Cited Count：11 Percentile：56.98(Materials Science, Multidisciplinary)Measurements of LBE flow velocity profile were realized in the spallation target model by the ultrasonic Doppler velocity profile technique. Hitherto, it has not yet been done well because both of poor wetting property of LBE with stainless steels and poor performance of supersonic probes at high temperatures. Measurement was made for a return flow in the target model, which has coaxially arranged annular and tube channels. The electromagnetic pump generates LBE flow and the flow rate was measured by the electromagnetic flow meter. Measurement results show that re-circulation occurred near the surface of beam window, which might affect a heat transfer of target container.
Liu, W.; Nariai, Hideki*
Journal of Heat Transfer, 127(2), p.149 - 158, 2005/02
Times Cited Count：12 Percentile：46.02(Thermodynamics)Homogeneous nucleation, although being discounted as a mechanism for vapor formation for water in most conditions, is found being possible to occur under some extreme conditions in subcooled flow boiling. In this paper, firstly, the existence of the homogeneous nucleation governed condition is indicated. Followed, a criterion is developed to judge a given working condition is the conventional one or the homogeneous nucleation governed one. With the criterion, subcooled flow boiling data are categorized and typical homogeneous nucleation governed datasets are listed. CHF triggering mechanism for the homogeneous nucleation governed condition is proposed and verified. Parametric trends of the CHF, in terms of mass flux, pressure, inlet subcooling, channel diameter and the ratio of heated length to diameter are also studied.
Ezato, Koichiro; Dairaku, Masayuki; Taniguchi, Masaki; Sato, Kazuyoshi; Suzuki, Satoshi; Akiba, Masato; Ibbott, C.*; Tivey, R.*
Fusion Science and Technology, 46(4), p.530 - 540, 2004/12
Times Cited Count：14 Percentile：66.09(Nuclear Science & Technology)The first fabrication and heating test of a large-scale CFC monoblock divertor mock-up using annular flow concept have been performed to demonstrate its manufacturability and thermo-mechanical performance. Prior to the fabrication of the mock-up, brazed joint tests between the CFC monoblock and the CuCrZr tube have been carried out to find the suitable heat treatment mitigating loss of the high mechanical strength of the CuCrZr material. Basic mechanical examination on CuCrZr undergoing the brazing heat treatment and FEM analyses are also performed to support the design of the mock-up. High heat flux tests on the large-scale divertor mock-up have been performed in an ion beam facility. The mock-up has successfully withstood more than 1,000 thermal cycles of 
for 15 s and 3,000 cycles more than 
for 15 s, which simulates the heat load condition of the ITER divertor. No degradation of the thermal performance of the mock-up has been observed throughout the thermal cycle test.
Hattori, Hirofumi*; Sato, Hiroshi; Nagano, Yasutaka*
Nihon Kikai Gakkai Rombunshu, B, 70(696), p.1919 - 1926, 2004/08
no abstracts in English
Toda, Saburo*; Yuki, Kazuhisa*; Akimoto, Hajime
JAERI-Tech 2004-008, 58 Pages, 2004/03
JAERI-Tech-2004-008.pdf:5.14MB
no abstracts in English
Asakura, Nobuyuki
Purazuma, Kaku Yugo Gakkai-Shi, 80(3), p.190 - 200, 2004/03
Understanding of the divertor and Scrape-off Layer (SOL) plasmas has been progressed during improvements of the compact- and closed-geometry tokamak divertors. Developments of new diagnostics viewing the SOL and upstream of the divertor target (with the finest spatial and/or time resolutions) have contributed to understand the physics mechanisms under large variations of the plasma along and perpendicular to the field lines. Four topics: (i) heat and particle transports upstream of the divertor plate, (ii) burst transport of heat and particles towards the divertor, (iii) SOL plasma flow, and (iv) plasma diffusion in SOL, were reviewed.
Nishihara, Tetsuo; Shimizu, Akira; Inagaki, Yoshiyuki; Tanihira, Masanori*
Nihon Genshiryoku Gakkai Wabun Rombunshi, 2(4), p.517 - 524, 2003/12
no abstracts in English
Aso, Tomokazu; Sato, Hiroshi; Kaminaga, Masanori; Hino, Ryutaro; Monde, Masanori*
Proceedings of ICANS-XVI, Volume 2, p.935 - 944, 2003/07
no abstracts in English
Shibamoto, Yasuteru; Sagawa, Jun*; Kukita, Yutaka*; Nakamura, Hideo
Konsoryu, 17(2), p.171 - 179, 2003/06
A bifunctional probe was developed for simultaneous, high-speed measurement of local temperature and phase of fluid at the same place. It was designed for application to water/melt multi-phase experiments involving transient boiling of water on the surface of molten metal. An unsheathed thermocouple (TC) of a small wire diameter was used for phase detection, that is distinction of melt/water/vapor phase, as well as for temperature measurement of each phase. The phase was detected by measuring the electric impedance between the TC and the ground. A 100-kHz AC signal was imposed on the TC wire for this purpose. The AC signal was filtered out from the temperature signal before it was amplified. With the first design of low-pass filter (LPF), however, a large noise was induced in the temperature signal every time the TC was grounded electrically by contact with molten metal. This problem was overcome by redesigning the LPF. The final design succeeded in measuring the quick movements of interface and the temperature changes in the individual phases in a water-melt-vapor multiphase flow.
Iguchi, Tadashi; Shibamoto, Yasuteru; Asaka, Hideaki; Nakamura, Hideo
Proceedings of 11th International Conference on Nuclear Engineering (ICONE-11) (CD-ROM), 8 Pages, 2003/04
Authors investigated the cooling limit under flow instability, by conducting THYNC experiments using a 22 bundle test section of electrical rod heaters、whose heated lengths and diameters were 3.71m and 12.3mm. The experimental result indicated periodic rise and rapid drop of the rod temperature under flow oscillation, indicating periodic film boiling. When the heating power increased further, the rod temperature indicated continuous film boiling. The power at the onset of continuous film boiling (cooling limit) under flow oscillation was about 50%-80% of the cooling limit under steady flow condition in THYNC. The ratio of both cooling limits almost agreed with the Umekawa model prediction in cases of P
2MPa and G400kg/m2s. For high pressure and high mass flux conditions, the ratio almost agreed with the empirical model based on the heat balance during one cycle of flow oscillation. TRAC-BF1 code simulated periodic film boiling qualitatively, but the cooling limit under the flow oscillation was not predicted well probably due to inaccurate rewetting prediction.
Kurihara, Ryoichi
Fusion Engineering and Design, 61-62, p.209 - 216, 2002/11
Times Cited Count：4 Percentile：29.25(Nuclear Science & Technology)To attain high fusion power density, the divertor must suffer high heat flux from the fusion plasma. It is very difficult to remove a high heat flux more than 20 MW/m
using the only solid divertor plate from the viewpoint of severe mechanical state such as thermal stress and crack growth. Therefore, a concept of liquid divertor is proposed to remove high heat flux by liquid films flowing on a solid wall. This paper mainly descries a preliminary thermofluid analysis of the free surface liquid flow, made of the FliBe molten salt, using the finite element analysis code ADINA-F. The heat flux of 25
100 MW/m was given on the free surface liquid of the flow. I explored a possibility of applying the secondary flow to enhance the heat transfer of the liquid flow suffering high heat flux. This analysis shows that the heat flux of 100 MW/m can be removed by inducing the secondary flow in the free surface liquid FLiBe. And this paper shows that the liquid divertor using solid-liquid multi-phase flow makes possible large heat removal by utilizing the latent heat of fusion of solid phase.
Kataoka, Isao*; Matsuura, Keizo*; Yoshida, Kenji*
JAERI-Tech 2002-015, 83 Pages, 2002/03
JAERI-Tech-2002-015.pdf:3.62MB
no abstracts in English
Kaminaga, Fumito*
JAERI-Tech 2002-012, 68 Pages, 2002/03
JAERI-Tech-2002-012.pdf:2.45MB
no abstracts in English
Kondo, Masaya; Nakamura, Hideo; Anoda, Yoshinari; Saishu, Sadanori*; Obata, Hiroyuki*; Shimada, Rumi*; Kawamura, Shinichi*
Proceedings of 10th International Conference on Nuclear Engineering (ICONE 10) (CD-ROM), 9 Pages, 2002/00
no abstracts in English
Ishiyama, Shintaro; Muto, Yasushi; Ogata, Hiroshi*; Kamito, Yoshimi*
Nihon Genshiryoku Gakkai-Shi, 43(7), p.708 - 717, 2001/07
Times Cited Count：3 Percentile：27.1(Nuclear Science & Technology)no abstracts in English
Konno, Chikara; Maekawa, Fujio; Kasugai, Yoshimi; Uno, Yoshitomo; Kaneko, Junichi; Nishitani, Takeo; Wada, Masayuki*; Ikeda, Yujiro; Takeuchi, Hiroshi
Nuclear Fusion, 41(3), p.333 - 337, 2001/03
Times Cited Count：3 Percentile：10.97(Physics, Fluids & Plasmas)no abstracts in English
