Igarashi, Yu; Yamaguchi, Ichiro*; Oda, Keiji*; Fukushi, Masahiro*; Sakama, Minoru*; Iimoto, Takeshi*
Nihon Hoshasen Anzen Kanri Gakkai-Shi, 21(2), p.74 - 76, 2022/11
no abstracts in English
Kano, Koichi*; Hagiwara, Satoshi*; Igarashi, Takahiro; Otani, Minoru*
Electrochimica Acta, 377, p.138121_1 - 138121_10, 2021/05
We investigated the free corrosion potential at an interface between an Al electrode and an aqueous NaCl solution under acidic conditions via density functional theory combined with the effective screening medium and reference interaction site model (ESM-RISM). The electrode potentials for the anodic and cathodic corrosion reactions were obtained from the grand potential profile as a function of the electron chemical potential at the interface. Thereafter, we determined the free corrosion potential using the Tafel extrapolation method. The results of the free corrosion potential were consistent with previous experimental data. By controlling the pH, we determined the pH dependence of the free corrosion potential, and the results agreed well with the experimental results. Our results indicated that the ESM-RISM method duly described the environmental effect of an acidic solution and precisely determined the free corrosion potential.
Miyao, Tomoaki*; Igarashi, Zenei*; Miura, Akihiko; Mayama, Minoru*
Proceedings of 9th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.571 - 573, 2013/08
no abstracts in English
Kobayashi, Takayuki; Isayama, Akihiko; Fasel, D.*; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Sawahata, Masayuki; Suzuki, Sadaaki; Terakado, Masayuki; Hiranai, Shinichi; et al.
Journal of Plasma and Fusion Research SERIES, Vol.9, p.363 - 368, 2010/08
Improvements are required for expanding the pulse length of the JT-60 ECRF system (5s) for JT-60SA (100s). Newly developed power supplies will be fabricated and installed by EU. The conditioning operation of an improved gyrotron equipping a newly designed mode convertor has been started. The mode convertor will reduce heat flux on the internal components and therefore expected to enable long pulse operation at 1 MW. Pre-programmed and/or feedback control of the heater current and anode voltage, which was successfully demonstrated in JT-60U, will be key techniques because the beam current decreases during a shot. The evacuated transmission lines have a capability of 1 MW per line. Since maintenance of the components in the vacuum vessel is difficult, a linear motion antenna concept was proposed to reduce risks of water leakage and fault of the driving mechanism in the vacuum vessel. The detailed design and the low power test of a mock-up antenna have been started.
Kamide, Hideki; Igarashi, Minoru*; Kawashima, Shigeyo*; Kimura, Nobuyuki; Hayashi, Kenji
Nuclear Engineering and Design, 239(1), p.58 - 67, 2009/01
Water experiments were carried out for thermal hydraulic aspects of thermal striping in a mixing tee, which has main to branch diameter ratio of 3. Detailed temperature and velocity fields were measured by a movable thermocouple tree and particle image velocimetry. Flow patterns in the tee were classified into three groups, which had own temperature fluctuation profiles. The power spectrum density (PSD) of temperature fluctuation showed an unique profile, which is normalized by St number, when the flow velocity ratio and flow pattern was identical. Numerical simulation based on finite difference method showed alternative vortex development behind the jet from the branch pipe in a case of wall jet. Mixing behavior in the tee was discussed based on the measured data and the simulation.
Kamide, Hideki; Igarashi, Minoru; Kimura, Nobuyuki; Hayashi, Kenji
Saikuru Kiko Giho, (27), p.41 - 53, 2005/06
When temperature fluctuation in fluid is transferred to the structure, it induces thermal load via thermal expansion of the structure. If the fluid temperature fluctuation amplitude and then thermal stress are large, structural integrity might be lost due to high cycle thermal fatigue, i.e., thermal striping. Water experiments were carried out for thermal hydraulic aspects of the thermal striping. A mixing tee and a triple-parallel jet along wall were selected as the test geometry. Detailed temperature and velocity fields were measured by movable thermocouple trees and particle image velocimetry. The power spectrum density (PSD) of temperature fluctuation could be estimated by a universal line, which is normalized by St number, when the flow velocity ratio and flow pattern was identical. Comparison of frequency characteristics between the temperature and velocity showed that the temperature fluctuation in the mixing tee was caused by Karman vortex behind the jet exiting from the branch pipe in case of wall jet condition.
Kamide, Hideki; Kimura, Nobuyuki; Igarashi, Minoru; Hayashi, Kenji
Proceedings of 6th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, Operations and Safety (NUTHOS-6) (CD-ROM), 0 Pages, 2004/10
Experimental Study was carried out for evaluation of thermal hydraulics of thermal striping. Parallel-triple jet along a wall and mixing tee experiments and experimenatl analyses using DINUS-3 code were performed. Decay of fluctuation intensity near the wall was found. Calculated results of temperature and velocity fields were in good agreement with experimental data.
Tanaka, Masaaki; Kawashima, Shigeyo*; Igarashi, Minoru; Hayashi, Kenji; Tobita, Akira; Kamide, Hideki
JNC TN9400 2003-117, 65 Pages, 2004/03
Temperature fluctuation due to mixing of hot and cold fluids gives thermal fatigue to the structure (thermal striping phenomena).Investigation of this phenomenon is significant for the safety of a fast breeder reactor, which uses liquid metal as a coolant. In Japan Nuclear Cycle Development Institute, experiments and numerical analyses have been carried out to understand this phenomenon and also to construct the evaluation rule, which can be applied to the design. A water experiment of fluid mixing in T-pipe with long cycle fluctuation (WATLON),which notices thermal striping phenomena in the T-pipe junction, is performed to investigate the key factor of mixing phenomena by reason of long cycle fluctuation observed in a plant. By the former visualization test, it was showed that the flow pattern of branch pipe jet could be classified into (A) impinging jet, (B) deflecting jet (C) re-attachment jet and (D) wall jet according to the inflow condition. It was confirmed that the each jet pattern could be predicted by the momentum ratio of the each piping fluid. In this study, a thermo-chromic liquid crystal sheet was put on the inner wall in the main pipe, and temperature field on the wall surface was visualized. We established a new method to convert the color image data to temperature data. And measurement uncertainty of this method was evaluated + and - about 2.0 [deg-C], using by the typical picture in the temperature calibration test. From the temperature fluctuation visualization test by liquid crystal sheet, the cold spot was formed in just downstream region from the outlet of the branch pipe in the cases of the wall jet and impinging jet. Since this cold spot moved in time, high value of temperature fluctuation intensity was shown around the cold spot. And the validity of this method was shown from the comparison of the thermocouple data installed in a wall surface with the temperature conversion result.
; Igarashi, Minoru; Kamide, Hideki; Tanaka, Masaaki; Kimura, Nobuyuki
Nihon Kikai Gakkai Rombunshu, B, 70(700), p.3150 - 3157, 2004/00
Research of thermal striping phenomenon is significant for the safety of a fast reactor. In this study, a water experiment for thermal hydraulics in T junction was performed to investigate thermal striping phenomena. Measurement of flow velocity using particle image velocimetry and detailed temperature measurement using a movable thermocouple tree were carried out to clarify mixing phenomena in T junction. The velocity measurement showed that, in the wall jet case, the vortices were generated in the wake region behind the branch pipe jet. This vortex was correlated with prominent frequency of the temperature fluctuation. As a method of evaluating the frequency characteristic of temperature fluctuation, normalized power spectrum density (PSD) was proposed.
Igarashi, Minoru; Tanaka, Masaaki; Kimura, Nobuyuki; Nakane, Shigeru*; Kawashima, Shigeyo*; Hayashi, Kenji; Tobita, Akira; Kamide, Hideki
JNC TN9400 2003-092, 100 Pages, 2003/11
A water experiment for thermal hydraulics in a mixing tee was performed to investigate thermal striping phenomena. Measurement of flow velocity using particle image velocimetry and temperature measurement were carried out. Normalized power spectrum density of temperature fluctuation had same profile, when the momentum ratio of the main and branch pips is the same. From the velocity measurement test, when the momentum ratio is the same, flow pattern at mixing region shows the alomost same tendency. Temperature transfer characteristics from fluid to structure can be estimated by a constant heat transfer coefficient in time.
Sato, Hiroyuki; Igarashi, Minoru; Kimura, Nobuyuki; Kamide, Hideki
JNC TN9400 2003-079, 38 Pages, 2003/09
Gas entrainment due to high flow velocity in the UIS slit is one of major point of reactor vessel design. A 1/20th scaled model water experiment for a reactor vessel upper plenum was performed to evaluate flow through a slit in the column type UIS, fundamental behavior of reactor upper plenum flow, and survey some devices which reduce flow velocity through the slit and optimize flow in the plenum.The results are as follows. The outer shroud had effects to bend the jet through the UIS slit toward the reactor vessel wall and also to flatten flow exiting from the UIS. And flow guide was set beside of the slit of UIS baffle plate to reduce the jet velocity in the UIS slit using Coanada effect, the maximum effect was seen by using around shape guide.
Kimura, Nobuyuki; Miyake, Yasuhiro*; Miyakoshi, Hiroyuki; Nagasawa, Kazuyoshi*; Igarashi, Minoru; Kamide, Hideki
JNC TN9400 2003-077, 96 Pages, 2003/06
A quantitative evaluation on thermal striping, in which temperature fluctuation due to convective mixing causes high cycle thermal fatigue in structural components, is of importance for structural integrity and reactor safety.Thermal conductivity of sodium is approximately 100 times larger than that of water. Thus, temperature fluctuation characteristics will be different between sodium, which is used as a coolant of a fast reactor, and water, which is used in general industries. In this study, a comparison of convective mixing among jets was performed in parallel triple wall jets with the same geometries between sodium and water. The discharged velocity in the sodium experiment was experimental parameter and set at the same velocity and the same Reynolds number in comparison with the water experiment. And also, the velocity ratio among the triple jets was varied to change flow pattern. It was seen that the water jets were mixed in slightly closer region to the nozzle than in sodium jets. As for the power spectrum densities (PSD) of temperature fluctuation, the PSD of sodium was similar to the PSD of water under the same discharged velocity condition. At the neighborhood of the wall, the lower frequency component in the PSD of sodium decreased in comparison with the PSD of water. It was shown that the amplitude and frequency characteristics obtained by rain-flow method, which was important to evaluate structural damage by the thermal fatigue, were identical between sodium and water overall. These experimental results show that water experiment could simulate the frequency and the amplitude in temperature fluctuation characteristics in the sodium cooled reactor.
Kimura, Nobuyuki; Hayashi, Kenji; Ito, Masami*; Sekine, Tadashi*; Igarashi, Minoru; Sato, Hiroyuki; Kamide, Hideki
JNC TN9400 2003-032, 214 Pages, 2003/03
An innovative sodium cooled fast reactor has been investigated on the FBR feasibility study. The design of the reactor is undergoing in order to reduce the construction cost of the reactor. For example, thermal output is increased against the reactor size and an upper inner structure (UIS) has a slit for the arm of the fuel-handling machine to simplify the fuel exchanging system. The dipped plates (D/P) are set below the free surface to prevent gas entrainment at free surface. We performed an 1/10th scaled model water experiment for the upper plenum of reactor vessel and investigated flow fields in the plenum in order to optimize flow. In the upper plenum, all of main components were set up as well as the reactor design. In addition, the D/P has a hole in front of the slit of the UIS to insert the fuel handling machine(FHM). As the experimental parameters, the core outlet velocity was varied from the condition of the Froude number similarity to the same value as the real reactor. The local velocity was measured by the particle image velocimetry and the ultrasound Doppler velocimetry. In the experimental results, gas entrainment at the free surface was not observed in the range from the Froude number similarity condition to the same velocity condition as the real reactor. However, the free surface was bulged on a large scale in front of the UIS slit. At the neighborhood of the H/L intake, three vortex cavitations were observed. The vortex cavitations were broken out under the same cavitation coefficient condition based on the H/L velocity as that in the real reactor. A vertical rib was set on the reactor vessel wall near the H/L inlet to restrict the rotating flow at the neighborhood of the H/L. As the result, the vortex cavitation at the region between the reactor vessel wall and the H/L was supressed under the same cavitation factor condition as the real reactor. A vertical cylinder, named FHM plug, was installed to close the hole in the D/P fbr FHM.
Igarashi, Minoru; Kawashima, Shigeyo*; Nakane, Shigeru*; Tanaka, Masaaki; Kimura, Nobuyuki; Kamide, Hideki
JNC TN9400 2003-005, 80 Pages, 2003/02
In the place where hot and cold fluids are mixed, a time and spatial temperature fluctuation occurs. When this temperature fluctuation amplitude is large, it causes high cycle thermal fatigue in surrounding structure (thermal striping phenomena). Mixing area of high and low temperature fluid exists not only in an atomic power plant but also in a general plant, then, it is significant to investigate this phenomena and also to establish an evaluation rule. In Japan Nuclear Cycle Development Institute, several experiments and the improvement of the analysis methods have been carried out to understand thermal striping phenomena and also to construct an evaluation rule, which can be applied to design. Water Experiment on Fluid Mixing in T-pipe with Long Cycle Fluctuation (WATLON), aiming at examining thermal striping phenomena in a mixing tee, is performed to investigate key factors of mixing phenomena. In this study, in order to investigate the fluid mixing phenomena, temperature and flow velocity distribution were measured by movable thermocouple tree and particle image velocimetory (PIV). And the analysis using a in-house direct numerical simulation (DNS) code, DINUS-3 was performed to understand applicability of the analytical method in mixing tee. The temperature and velocity fields obtained from the DINUS-3 were in good agreement with the experimental results. And the prominent frequency of temperature fluctuation was also in good agreement. The DINUS-3 calculation simulated vortex structure in the wake region behind the branch pipe jet. The results of analysis showed that a Karman vortex generated in the wake region behind the branch pipe jet influenced the temperature fluctuation behavior in the mixing tee. And the analytical results revealed that the vortex generated in the wake region behind the branch pipe jet showed the 3-dimensional behavior.
Kimura, Nobuyuki; Hayashi, Kenji; Igarashi, Minoru; Kamide, Hideki; Ito, Masami*; Sekine, Tadashi*
Proceedings of 10th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-10), CD-RO, K0102 Pages, 2003/00
An innovative sodium cooled fast reactor has been investigated on the feasibility study of FBR cycle system in JNC. A compact reactor vessel (R/V) and a column type upper inner structure (UIS) with a radial slit for an arm of a fuel-handling machine (FHM) are adopted. Dipped plates (D/P) are set in the R/V below the free surface to prevent gas entrainment at free surface. We performed an 1/10th scaled model water experiment for the upper plenum of the R/V. Gas entrainment at the free surface was not observed in the experiment under the same velocity condition as the designed reactor. However, the free surface rose in front of the UIS slit due to upward flow through the gap between the D/P and the R/V wall. The upward flow will cause free surface vortex and also the gas entrainment. Three vortex cavitations were observed near the hot leg (H/L) inlet. The vortex cavitations were broken out under the same cavitation factor condition as the reactor. A vertical rib was set on the R/V wall
Kimura, Nobuyuki; Nagasawa, Kazuyoshi*; Miyakoshi, Hiroyuki; Miyake, Yasuhiro*; Igarashi, Minoru; Kamide, Hideki
JNC TN9400 2003-003, 66 Pages, 2002/10
A quantitative evaluation on thermal striping, in which temperature fluctuation due to convective mixing causes high cycle thermal fatigue in structural components, is of importance for reactor safety. The reasonable and safety design could be approved by taking account of decay of temperature fluctuation in fluid, during heat transfer from fluid to structural surface and thermal conduction in the structure. Temperature fluctuation characteristics due to convective mixing will be influenced by the velocity/temperature boundary layers near the structure. In this study, an experimental analysis was performed using DNS in order to separate influence of heat capacity of the structure and to evaluate an attenuation due to the boundary layer near the wall surface for a sodium experiment of parallel triple jets configuration. In the experiment, a cold jet on center and hot jets on both sides flowed vertically and along the wall, and the discharged velocities of triple jets were O.5m/s equally. The calculated temperature field was in good agreement with the experimental result at further position from the wall surface, including the power spectrum density of the temperature fluctuation. On the other hand, at near position from the wall surface, calculated temperature fluctuation intensity was not attenuated whereas the experimental intensity was decreased. This means that the intensity of temperature fluctuation is not decreased by the boundary layer. Thermal interaction between fluid and the wall will decrease the temperature fluctuation intensity in the fluid near the wall. The effect of wall friction on second moments of turbulence was evaluated.
Hidaka, Akihide; Maruyama, Yu; Igarashi, Minoru*; Hashimoto, Kazuichiro; Sugimoto, Jun
Nuclear Engineering and Design, 200(1-2), p.303 - 315, 2000/08
no abstracts in English
Morii, Yukio; Koike, Yoshihiro; Igarashi, Takeshi*; Kubota, Minoru*; Hiresaki, Yu*; Tanida, Koji*
Physica B; Condensed Matter, 284-288(Part2), p.2014 - 2015, 2000/07
no abstracts in English
Maruyama, Yu; Shibazaki, Hiroaki*; Igarashi, Minoru*; Maeda, Akio; Harada, Yuhei; Hidaka, Akihide; Sugimoto, Jun; Hashimoto, Kazuichiro*; Nakamura, Naohiko*
Journal of Nuclear Science and Technology, 36(5), p.433 - 442, 1999/05
no abstracts in English
Koike, Yoshihiro; Morii, Yukio; Igarashi, Takeshi*; Kubota, Minoru*; Hiresaki, Yu*; Tanida, Koji*
Cryogenics, 39(7), p.579 - 583, 1999/00
no abstracts in English