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Journal Articles

Measurement of fragments of a wall-impinging liquid jet in a shallow pool

Horiguchi, Naoki; Yoshida, Hiroyuki; Kaneko, Akiko*; Abe, Yutaka*

Proceedings of 12th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS12) (Internet), 6 Pages, 2022/10

For safety evaluation of nuclear reactors in severe accidents, it is important to estimate physical quantities of fragments generated from the molten fuel jet, which falls in a pool and breaks up. The evaluation method has been developed for the behavior as liquid jet with hydrodynamic interaction including fuel coolant interaction (FCI). In case of a shallow pool assumed in ex-vessel, the molten fuel jet is assumed to behave as wall-impinging liquid jet and to form liquid film flow spreading on the floor with/without fragmentation. In our research, focusing on hydrodynamic interaction and the transient 3-dimensional spreading on the floor, we have developed the evaluation method by numerical simulation using the two-phase flow simulation code with interface tracking method (TPFIT) developed by JAEA and, the experimental method using the 3D-LIF method in liquid-liquid system for the validation data. In our previous studies, we investigated the wall-impinging liquid jet behavior with fragmentation and observed that the liquid film flow had some characteristic parts transiently. Since it indicates that the quantities change depending on the parts and affect the safety evaluation, it is important to measure the quantities of the fragments generated from each part. This paper explains the measurement of the physical quantities of the fragments generated from each part of the wall-impinging liquid jet in a shallow pool for the validation of the numerical simulation. We conducted an experiment with the 3D-LIF method and segmented the experimental data based on the fragmentation point over the liquid film flow using the dispersed phase tracking method, developed by JAEA. Then, we measured the diameter and amount of the fragments from the segmented experimental data and investigated their changing trend.

Journal Articles

Applicability of equivalent linear analysis to reinforced concrete shear walls; 3D FEM simulation of experiment results of seismic wall ultimate behavior

Ichihara, Yoshitaka*; Nakamura, Naohiro*; Moritani, Hiroshi*; Horiguchi, Tomohiro*; Choi, B.

Nihon Genshiryoku Gakkai Wabun Rombunshi, 21(1), p.1 - 14, 2022/03

In this study, we aim to approximately evaluate the effect of nonlinearity of reinforced concrete structures through seismic response analysis using the equivalent linear analysis method. A simulation analysis was performed for the ultimate response test of the shear wall of the reactor building used in an international competition by OECD/NEA in 1996. The equivalent stiffness and damping of the shear wall were obtained from the trilinear skeleton curves proposed by the Japan Electric Association and the hysteresis curves proposed by Cheng et al. The dominant frequency, maximum acceleration response, maximum displacement response, inertia force-displacement relationship, and acceleration response spectra of the top slab could be simulated well up to a shear strain of approximately $$gamma$$=2.0$$times$$10$$^{-3}$$. The equivalent linear analysis used herein underestimates the maximum displacement response at the time of ultimate fracture of approximately $$gamma$$=4.0$$times$$10$$^{-3}$$. Moreover, the maximum shear strain of the shear wall could not capture the locally occurring shear strain compared with that of the nonlinear analysis. Therefore, when employing this method to evaluate the maximum shear strain and test results, including those during the sudden increase in displacement immediately before the fracture, sufficient attention must be paid to its applicability.

Journal Articles

Correction method of measurement volume effects on time-averaged statistics for laser Doppler velocimetry

Wada, Yuki; Furuichi, Noriyuki*; Tsuji, Yoshiyuki*

European Journal of Mechanics B, Fluids, 91, p.233 - 243, 2022/01

 Times Cited Count:1 Percentile:25.01(Mechanics)

Journal Articles

3D FEM soil-structure interaction analysis for Kashiwazaki-Kariwa Nuclear Power Plant considering soil separation and sliding

Ichihara, Yoshitaka*; Nakamura, Naohiro*; Moritani, Hiroshi*; Choi, B.; Nishida, Akemi

Frontiers in Built Environment (Internet), 7, p.676408_1 - 676408_14, 2021/06

The objective of this study is the improvement of response evaluations of structures, facilities and equipment in evaluation of three-dimensional seismic behavior of nuclear power plant facilities, by three-dimensional finite element method model, including separation and sliding between the soil and the basement walls. To achieve this, simulation analyses of Kashiwazaki Kariwa nuclear power plant unit 7 reactor building under the 2007 Niigataken-chuetsu-oki earthquake event were carried out. These simulation analyses consider soil-structure interaction using a three-dimensional finite element method model in which the soil and building are three-dimensionally modeled by the finite element method. It is found that basemat uplift is generated on east side of the basemat edge, and this has an important influence on the results. The importance is evidenced by the difference of local response in soil pressure characteristics beneath the edge of basemat, the soil pressure characteristics along the east side of basement wall and the maximum acceleration response at the west end of the embedded surface. Although, in this particular study, basemat uplift, separation and sliding have only a relatively small influence on the maximum acceleration response of embedded surface and the soil pressure characteristics along the basement walls and beneath the basemat, under strong earthquake motion, these influences can be significant, therefore appropriate evaluation of this effect should be considered.

Journal Articles

Electric field effect on the magnetic domain wall creep velocity in Pt/Co/Pd structures with different Co thicknesses

Koyama, Tomohiro*; Ieda, Junichi; Chiba, Daichi*

Applied Physics Letters, 116(9), p.092405_1 - 092405_5, 2020/03

AA2019-0550.pdf:0.91MB

 Times Cited Count:4 Percentile:27.96(Physics, Applied)

Journal Articles

Estimation of planes of a rock mass in a gallery wall from point cloud data based on MD PSO

Matsuura, Yuto*; Hayano, Akira; Itakura, Kenichi*; Suzuki, Yukinori*

Applied Soft Computing, 84, p.105737_1 - 105737_9, 2019/11

 Times Cited Count:2 Percentile:15.16(Computer Science, Artificial Intelligence)

LiDAR (laser imaging detection and ranging) has been developed to obtain a high-resolution point cloud data indicating the detailed 3D shapes of an object. To identify discontinuities in a rock mass of a tunnel gallery wall, it is necessary to approximate the rock mass surface with small planes. Normal vectors of the planes are important to identify discontinuities. We developed an algorithm for estimation of planes based on multi-dimensional particle swarm optimization (MD PSO) from point cloud data. Point cloud data were segmented into bounding boxes and grouped into clusters by MD PSO. Planes were estimated using the least squares method for point cloud data in the respective clusters. The newly developed MD PSO algorithm was evaluated using point cloud data obtained from a gallery wall. Evaluation was carried out in comparison with the previous developed variable-box segmentation (VBS) algorithm. The MD PSO-based algorithm showed a 7% higher accuracy than that of the VBS algorithm.

Journal Articles

Experimental evaluation of wall shear stress in a double contraction nozzle using a water mock-up of a liquid Li target for an intense fusion neutron source

Kondo, Hiroo*; Kanemura, Takuji*; Park, C. H.*; Oyaizu, Makoto*; Hirakawa, Yasushi; Furukawa, Tomohiro

Fusion Engineering and Design, 146(Part A), p.285 - 288, 2019/09

 Times Cited Count:1 Percentile:11.65(Nuclear Science & Technology)

Herein, the wall shear stress in a double contraction nozzle has been evaluated experimentally to produce a liquid lithium (Li) target as a beam target for intense fusion neutron sources such as the International Fusion Materials Irradiation Facility (IFMIF), the Advanced Fusion Neutron Source (A-FNS), and the DEMO Oriented Neutron Source (DONES). The boundary layer thickness and wall shear stress are essential physical parameters to understand erosion-corrosion by the high-speed liquid Li flow in the nozzle, which is the key component in producing a stable Li target. Therefore, these parameters were experimentally evaluated using an acrylic mock-up of the target assembly. The velocity distribution in the nozzle was measured by a laser-doppler velocimeter and the momentum thickness along the nozzle wall was calculated using an empirical prediction method. The resulting momentum thickness was used to estimate the variation of the wall shear stress along the nozzle wall. Consequently, the wall shear stress was at the maximum in the second convergent section in front of the nozzle exit.

Journal Articles

Electric field control of magnetic domain wall motion via modulation of the Dzyaloshinskii-Moriya interaction

Koyama, Tomohiro*; Nakatani, Yoshinobu*; Ieda, Junichi; Chiba, Daichi*

Science Advances (Internet), 4(12), p.eaav0265_1 - eaav0265_5, 2018/12

AA2018-0306.pdf:0.57MB

 Times Cited Count:47 Percentile:89.26(Multidisciplinary Sciences)

We show that the electric field (EF) can control the magnetic domain wall (DW) velocity in a Pt/Co/Pd asymmetric structure. With the application of a gate voltage, a significant change in DW velocity up to 50 m/s is observed, which is much greater than that observed in previous studies. Moreover, a DW velocity exceeding 100 m/s is clearly modulated. An EF-induced change in the interfacial Dzyaloshinskii-Moriya interaction (DMI) up to several percent is found to be the origin of the velocity modulation. The DMI-mediated velocity change shown here is a fundamentally different mechanism from that caused by EF-induced anisotropy modulation. Our results will pave the way for the electrical manipulation of spin structures and dynamics via DMI control, which can enhance the performance of spintronic devices.

Journal Articles

Industry development activities and applied laser research activities at Fukui branch of Japan Atomic Energy Agency

Furusawa, Akinori; Takenaka, Yusuke*; Nishimura, Akihiko; Mizutani, Haruki; Muramatsu, Toshiharu

Nihon Hozen Gakkai Dai-14-Kai Gakujutsu Koenkai Yoshishu, p.479 - 480, 2017/08

Industry development activities on applied laser research held at Fukui branch of Japan Atomic Energy Agency are reported. Industry development is inevitable in long-term vision and strategy for developing maintenance technology and establishing decommissioning technology. Fukui branch of JAEA has organized public seminar offering businesses to promote these activities and technology exchange for years. Here some examples offered in the current seminar are introduced concerning with laser technology. Finally, our goal and important point of view are discussed.

Journal Articles

Liquid divertor

Shimada, Michiya; Miyazawa, Junichi*

Purazuma, Kaku Yugo Gakkai-Shi, 92(2), p.119 - 124, 2016/02

AA2015-0751.pdf:0.61MB

Actively convected liquid metal divertor is promising for providing a solution for issues of DEMO reactors including heat removal and disruptions. This chapter gives an overview of the motivation, research history, recent development, future perspective and issues to be resolved.

Journal Articles

Measurement of the stochastic radial dose distribution for a 30-MeV proton beam using a wall-less tissue-equivalent proportional counter

Tsuda, Shuichi; Sato, Tatsuhiko; Ogawa, Tatsuhiko

Radiation Protection Dosimetry, 168(2), p.190 - 196, 2016/02

 Times Cited Count:2 Percentile:20.11(Environmental Sciences)

Deposit energy distribution in microscopic site in a living cell is important information for understanding of biological effects of energetic heavy ion beams. In this work, a wall-less tissue equivalent proportional counter has been used for the measurement of lineal energy (y) distributions and dose-mean of y (yD) at radial direction of 30 MeV H at TIARA, for the verification of the microdosimetric function of PHITS. The measured yf(y) summed in radial direction agree with the corresponding data from the microdosimetric calculations using the PHITS code fairly well. The yD of 30 MeV proton beam presents the smallest value at r = 0.0 and gradually increase with radial distance, while the values of heavy ions such as iron showed rapid decrease with radial distance. This experimental result demonstrates that the stochastic deposit energy distribution of high-energy protons in microscopic region is rather constant both in the core and in the penumbra region of the track structure.

Journal Articles

Impact of wall saturation on particle control in long and high-power-heated discharges in JT-60U

Nakano, Tomohide; Asakura, Nobuyuki; Takenaga, Hidenobu; Kubo, Hirotaka; Miura, Yukitoshi; Shimizu, Katsuhiro; Konoshima, Shigeru; Masaki, Kei; Higashijima, Satoru; JT-60 Team

Nuclear Fusion, 46(5), p.626 - 634, 2006/05

 Times Cited Count:20 Percentile:57.48(Physics, Fluids & Plasmas)

In order to understand plasma-wall interactions in a long time scale, the discharge pulse length has been extended from 15 s to 65 s, with the NB-heating duration extended to 30 s. Nearly-saturation of the divertor plates was observed in the latter half of long pulse ELMy H-mode discharges. Particle sink into the divertor plates gradually decreased, and subsequently, wall-pumping efficiency became zero. This wall saturation resulted in a rise of the main plasma density without any auxiliary particle supply besides NB with divertor-pumping. Even when the total injected energy reached up to $$sim$$ 350 MJ in a discharge, neither sudden increase of carbon generation such as carbon bloom nor increase of the dilution of the main plasma was observed.

Journal Articles

High flux ion beam acceleration at the 100-eV level for fusion plasma facing material studies

Yoshida, Hajime; Yokoyama, Kenji; Taniguchi, Masaki; Ezato, Koichiro; Suzuki, Satoshi; Akiba, Masato

Fusion Engineering and Design, 81(1-7), p.361 - 366, 2006/02

 Times Cited Count:2 Percentile:17.23(Nuclear Science & Technology)

A 100 V level, high-flux, large area and steady-state ion beam acceleration has been developed for the investigation of the interactions between fusion edge plasmas and plasma facing materials. We have developed the new electrodes and installed them in the Super Low Energy Ion Source (SLEIS). Obtained hydrogen ion flux is comparable to those of conventional high-flux ion source ($$>$$1020 H/m$$^{2}$$s), though the accelerated voltage is extremely low (60-200 eV). This 100 V level ion beam acceleration will be useful to investigate the plasma wall interaction in divertor.

Journal Articles

First wall and divertor engineering research for power plant in JAERI

Suzuki, Satoshi; Ezato, Koichiro; Hirose, Takanori; Sato, Kazuyoshi; Yoshida, Hajime; Enoeda, Mikio; Akiba, Masato

Fusion Engineering and Design, 81(1-7), p.93 - 103, 2006/02

 Times Cited Count:12 Percentile:63.28(Nuclear Science & Technology)

This paper presents an R&D activity on the plasma facing components (PFCs), such as first wall and divertor, for the fusion power plant. The PFCs of the power plant will be subjected to heavy neutron irradiation and high heat/particle flux from plasma during the continuous operation. In the present design of the PFCs, the candidate structural material is a reduced activation ferritic-martensitic steel, F82H, from the viewpoints of low activation and high robustness against neutron irradiation, and the candidate armor material is tungsten from the low sputtering yield and low tritium retention points of view. To realize the PFCs using such materials, JAERI has bee extensively conducting R&Ds on; (1) high performance cooling tube, (2) tungsten armor materials, (3) selection of a bonding technique for F82H and tungsten materials and (4) evaluation of structural integrity. Recent achievements on these R&Ds are presented.

Journal Articles

Blanket-plasma interaction in tokamaks; Implication from JT-60U, JFT-2M and reactor studies

Kikuchi, Mitsuru; Nishio, Satoshi; Kurita, Genichi; Tsuzuki, Kazuhiro; Bakhtiari, M.*; Kawashima, Hisato; Takenaga, Hidenobu; Kusama, Yoshinori; Tobita, Kenji

Fusion Engineering and Design, 81(8-14), p.1589 - 1598, 2006/02

 Times Cited Count:4 Percentile:30.83(Nuclear Science & Technology)

Blanket-plasma interaction is important for plasma performance enhancement and reliability of first-wall/ blanket. Typical examples are harminization of wall stabilization and reduction of EM force during current quench, error field effect by ferritic steel, neutral-wall interaction under wall saturation, etc. JAERI reactor studies, JT-60U and JFT-2M results on this topics will be described.

Journal Articles

Conference summary; Progress in experiments on confinement, plasma-material interactions and innovative confinement concepts

Ninomiya, Hiromasa

Nuclear Fusion, 45(10), p.S13 - S31, 2005/10

 Times Cited Count:0 Percentile:0.01(Physics, Fluids & Plasmas)

This paper summarizes the results presented at the 20th IAEA Fusion Energy Conference 2004 in the sessions of confinement, plasma-wall interaction and innovative confinement concept. The highlights of the presentations are as follows. Long pulse operation with high beta and high bootstrap fraction much longer than the current diffusion time has been achieved. The discharge scenario optimization and its extrapolation towards ITER have progressed remarkably. Significant progress has been made in understanding of global confinement and transport physics.

Journal Articles

Overview of goals and performance of ITER and strategy for plasma-wall interaction investigation

Shimada, Michiya; Costley, A. E.*; Federici, G.*; Ioki, Kimihiro*; Kukushkin, A. S.*; Mukhovatov, V.*; Polevoi, A. R.*; Sugihara, Masayoshi

Journal of Nuclear Materials, 337-339, p.808 - 815, 2005/03

 Times Cited Count:63 Percentile:96.31(Materials Science, Multidisciplinary)

ITER is an experimental fusion reactor for investigation and demonstration of burning plasmas, characterised of its heating dominated by alpha-particle heating. ITER is a major step from present devices and an indispensable step for fusion reactor development. ITER's success largely depends on the control of plasma-wall interactions(PWI), with power and particle fluxes and time scales one or two orders of magnitude larger than in present devices. The strategy for control of PWI includes the semi-closed divertor, strong fuelling and pumping, disruption and ELM control, replaceable plasma-facing materials and stepwise operation.

Journal Articles

Development of fabrication technology of ITER shielding blanket

Enoeda, Mikio

Koon Gakkai-Shi, 30(5), p.256 - 262, 2004/09

Fabrication technologies for ITER in-vessel components, especially the shielding blanket with the separable first wall panel has been developed. Hot Isostatic Pressing (HIP) has been applied to the bonding of Cu-alloy/stainless steel and beryllium/Cu-alloy. First wall mock-ups fabricated by using HIP were tested under high heat fluxes and showed sufficient heat removal and thermal fatigue performance. Water jet and electrical discharge machining have been applied to manufacture slots into the first wall panel and the shield block. With these technologies, a first wall panel prototype and a shielding block 1/2 mock-up were successfully fabricated.

Journal Articles

First wall and divertor materials as plasma facing components

Suzuki, Satoshi

Koon Gakkai-Shi, 30(5), p.243 - 247, 2004/09

Selection and the development of plasma facing materials for fusion devices, mainly ITER, are presented. For the divertor, CFC (Carbon fiber reinforced carbon composite) materials are utilized as plasma facing materials in the lower part of vertical targets in ITER. Since the design maximum heat flux to the vertical targets is 20 MW/m$$^{2}$$, CFC materials, which have higher thermal conductivity than pure copper, are preferable from a heat removal point of view. On the other hand, a plasma facing material of a dome and a liner is tungsten because tungsten has low sputtering yield and has relatively high thermal conductivity among metals. First wall covers 80% of the plasma facing area of ITER. The plasma facing material of the first wall should have good compatibility with plasma. Therefore, beryllium is utilized as a plasma facing material from the low contamination and the minimization of the oxygen impurity to the plasma points of view.

148 (Records 1-20 displayed on this page)