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Journal Articles

Coping with electrode polarization for development of DC-driven electrical impedance tomography

Hirose, Yoshiyasu; Sagawa, Jun*; Shibamoto, Yasuteru; Kukita, Yutaka

Flow Measurement and Instrumentation, 81, p.102006_1 - 102006_9, 2021/10

Journal Articles

The Dependence of pool scrubbing decontamination factor on particle number density; Modeling based on bubble mass and energy balances

Sun, Haomin; Shibamoto, Yasuteru; Hirose, Yoshiyasu; Kukita, Yutaka

Journal of Nuclear Science and Technology, 58(9), p.1048 - 1057, 2021/09

 Times Cited Count:0 Percentile:0.02(Nuclear Science & Technology)

no abstracts in English

JAEA Reports

Seismically-induced reactor coolant leakage as an allegedly-possible cause of accident at unit 1 of Fukushima Dai-ichi Nuclear Power Station

Kukita, Yutaka; Watanabe, Norio

JAEA-Technology 2014-036, 38 Pages, 2014/11

JAEA-Technology-2014-036.pdf:26.08MB

NAIIC emphasized the possibility of seismically-induced reactor coolant leakage and implied its causal connection to the accident, in particular at the Fukushima Daiichi Unit 1. This view of NAIIC has been addressed by the Accident Investigation Committee established by the Cabinet decision, NISA, and the Secretariat of NRA. Based on seismic response analyses, plant records and simulations, their reports uniformly note that seismically-induced leakage is unlikely to be a causal factor for the core damage though the possibility of insignificantly small leakage cannot be ruled out completely. Also refuted are some of the arguments made by NAIIC as grounds for suspecting safety-significant leakage. The present report re-examines the leak detection capability through the review of plant instruments and post-accident simulations, and adds some arguments in order to resolve the issue raised by NAIIC without technical ambiguity as far as possible. As well, the plant design uniqueness of Unit 1, the history of facility changes, the operating procedures and the actual operations are looked into to raise issues for further investigation.

Journal Articles

Latest design of liquid lithium target in IFMIF

Nakamura, Hiroo; Agostini, P.*; Ara, Kuniaki; Cevolani, S.*; Chida, Teruo*; Ciotti, M.*; Fukada, Satoshi*; Furuya, Kazuyuki*; Garin, P.*; Gessii, A.*; et al.

Fusion Engineering and Design, 83(7-9), p.1007 - 1014, 2008/12

 Times Cited Count:14 Percentile:70.31(Nuclear Science & Technology)

This paper describes the latest design of liquid lithium target system in IFMIF. Design requirement of the Li target is to provide a stable Li jet with a speed of 20 m/s to handle an averaged heat flux of 1 GW/m$$^{2}$$. A double reducer nozzle and a concaved flow are applied to the target design. On Li purification, a cold trap and two kinds of hot trap are applied to control impurities below permissible levels. Nitrogen concentration shall be controlled below 10 wppm by one of the hot trap. Tritium concentration shall be controlled below 1 wppm by an yttrium hot trap. To maintain reliable continuous operation, various diagnostics are attached to the target assembly. Among the target assembly, a back-plate made of RAFM is located in the most severe region of neutron irradiation (50 dpa/y). Therefore, two design options of replaceable back wall and their remote handling systems are under investigation.

Journal Articles

Small-scale experiment on subcooled water jet injection into molten alloy by using fluid temperature-phase coupled measurement and visualization

Shibamoto, Yasuteru; Kukita, Yutaka*; Nakamura, Hideo

Journal of Nuclear Science and Technology, 44(8), p.1059 - 1069, 2007/08

 Times Cited Count:13 Percentile:69.25(Nuclear Science & Technology)

no abstracts in English

Journal Articles

In-pile experiment in JMTR on the radiation induced surface activation (RISA) effect on flow-boiling heat transfer

Shibamoto, Yasuteru; Yonomoto, Taisuke; Nakamura, Hideo; Kukita, Yutaka*

Journal of Nuclear Science and Technology, 44(2), p.183 - 193, 2007/02

 Times Cited Count:4 Percentile:33.2(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Two-dimensional optical measurement of waves on liquid lithium jet simulating IFMIF target flow

Ito, Kazuhiro*; Ito, Taro*; Kukita, Yutaka*; Koterazawa, Hiroyuki*; Kondo, Hiroo*; Yamaoka, Nobuo*; Horiike, Hiroshi*; Ida, Mizuho; Nakamura, Hideo; Nakamura, Hiroo; et al.

Proceedings of 14th International Conference on Nuclear Engineering (ICONE-14) (CD-ROM), 6 Pages, 2006/07

Waves on a liquid-lithium jet flow, simulating a proposed high-energy beam target design, have been measured using an optical technique based on specular reflection of a single laser beam on the jet surface. The streamwise and spanwise fluctuations of the local free-surface slope were least-square fitted with a sinusoidal curve to makeup the signals lost due to the constriction in the optical arrangement. The waveform was estimated with an assumption that wave phase speed can be calculated using the dispersion relation for linear capillary gravity waves. The direction of propagation on the jet surface was also evaluated so that the wave amplitudes, calculated by integral of slope angle signal, agree consistently in streamwise and spanwise direction. These measurements and analyses show that the waves at the measurement location for a jet velocity of 1.2 m/s can best be represented by oblique waves with an inclination of 0.32 rad, a wavelength of 4.2 mm and a wave amplitude of about 0.06 mm.

Journal Articles

Two-dimensional optical measurement of waves on liquid lithium jet simulating IFMIF target flow

Ito, Kazuhiro*; Ito, Taro*; Kukita, Yutaka*; Koterazawa, Hiroyuki*; Kondo, Hiroo*; Yamaoka, Nobuo*; Horiike, Hiroshi*; Ida, Mizuho; Nakamura, Hideo; Nakamura, Hiroo; et al.

Proceedings of 14th International Conference on Nuclear Engineering (ICONE-14) (CD-ROM), 6 Pages, 2006/07

no abstracts in English

Journal Articles

Simultaneous measurement of fluid temperature and phase during water jet injection into high temperature melt

Shibamoto, Yasuteru; Kukita, Yutaka*; Nakamura, Hideo

Proceedings of 11th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-11) (CD-ROM), 15 Pages, 2005/10

no abstracts in English

Journal Articles

Indirect measurement of near-surface velocity and pressure fields based on measurement of moving free surface profiles

Shibamoto, Yasuteru; Kukita, Yutaka*; Nakamura, Hideo

Nihon Kikai Gakkai Rombunshu, B, 71(703), p.825 - 832, 2005/03

no abstracts in English

Journal Articles

BEM-based measurement of pressure field adjacent to moving free surface

Shibamoto, Yasuteru; Kukita, Yutaka*; Nakamura, Hideo

Proceedings of 5th International Conference on Multiphase Flow (ICMF 2004) (CD-ROM), p.217_1 - 217_9, 2004/05

no abstracts in English

Journal Articles

Local temperature and phase measurement in water-melt multiphase flow with bifunctional probe and electrical signal processing

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.

Journal Articles

System pressure effect on density-wave instability; Simplified model analysis and experiments

Shibamoto, Yasuteru; Iguchi, Tadashi; Nakamura, Hideo; Kukita, Yutaka*

Proceedings of 11th International Conference on Nuclear Engineering (ICONE-11) (CD-ROM), 11 Pages, 2003/04

The pressure effect on the onset of flow instability in a vertical upflow through a boiling channel is studied both analytically and experimentally. The analytical model is based on the Wallis-Heasley model for linear analysis of one-dimensional homogeneous two-phase flow in thermal equilibrium. The dead-time elements commonly used to represent the time lag in the responses of variables to the inlet velocity perturbation is replaced by first-order lag elements to allow the system characteristic equation to be solved analytically. This approach, although approximate, makes it much easier to identify the main contributor to the instability because the individual components are represented by separate terms in the characteristic equation. The predictions are in reasonable agreement with the data when the system pressure effect on the irreversible pressure loss in the two-phase region is appropriately considered based on calibration experiments.

Journal Articles

Water flow experiments and analyses on the cross-flow type mercury target with perforated plates

Haga, Katsuhiro; Kinoshita, Hidetaka; Kaminaga, Masanori; Hino, Ryutaro; Tagawa, Hisato*; Kukita, Yutaka*

Proceedings of 11th International Conference on Nuclear Engineering (ICONE-11) (CD-ROM), 8 Pages, 2003/04

The cross-flow type mercury target, in which mercury flows crossing the proton beam path, has been developed as the spallation target of the material and life science facility in the high intensity proton accelerator project. As a part of design optimization, we proposed a mercury target using perforated plates aiming to simplify the inner structure, to make the target assembling easier, and to decrease the assembling cost. Then, the effectiveness of the target structure was investigated by no-heat water experiments and computational analyses. A mockup model of the cross-flow type mercury target using perforated plates was fabricated with plexi-glass and the water flow field was measured using PIV technique and the results were compared with the analytical results. The cross-flow field was realized by perforated plates and the analytical results corresponded well with the experimental results in the proton beam path where the cooling of heat generation is important.

Journal Articles

Visualization and measurement of subcooled water jet injection into high-temperature melt by using high-frame-rate neutron radiography

Shibamoto, Yasuteru; Kukita, Yutaka*; Nakamura, Hideo

Nuclear Technology, 139(3), p.205 - 220, 2002/09

 Times Cited Count:25 Percentile:83.34(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Boiling and non-boiling water jet penetration into liquid metal pool

Yano, Sanae*; Kukita, Yutaka*; Tsuji, Yoshiyuki*; Shibamoto, Yasuteru

Proceedings of 3rd International Symposium on Advanced Energy Conversion Systems and Related Technologies (CD-ROM), 7 Pages, 2001/12

no abstracts in English

Journal Articles

Unsteady motion of parastic-capillary ripples on the gravity waves

Seki, Kosuke*; Tsuji, Yoshiyuki*; Kondo, Masaya; Kukita, Yutaka*

Nihon Kikai Gakkai 2001-Nendo Nenji Taikai Koen Rombunshu, p.9 - 10, 2001/00

no abstracts in English

Journal Articles

Experimental investigation on similarity between velocity and density profiles in density-scratified countercurrent flow in reactor horizontal leg

Shibamoto, Yasuteru; Yonomoto, Taisuke; Anoda, Yoshinari; Kukita, Yutaka*

Nuclear Engineering and Design, 201(1), p.83 - 98, 2000/09

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Free surface shear layer instabilities on a high-speed liquid jet

Ito, Kazuhiro*; Tsuji, Yoshiyuki*; Nakamura, Hideo; Kukita, Yutaka*

Fusion Technology, 37(1), p.74 - 88, 2000/01

no abstracts in English

Journal Articles

Behaior of a lighter fluid intrusion into a flowing heavier fluid in simulating reactor horizontal leg

Shibamoto, Yasuteru; Kukita, Yutaka*; Yonomoto, Taisuke; Anoda, Yoshinari

Proceedings of 2nd Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-2), p.374 - 380, 2000/00

no abstracts in English

183 (Records 1-20 displayed on this page)