Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Ariyoshi, Gen; Saruta, Koichi; Kogawa, Hiroyuki; Futakawa, Masatoshi; Maeno, Koki*; Li, Y.*; Tsutsui, Kihei*
Proceedings of 20th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-20) (Internet), p.1407 - 1420, 2023/08
Cavitation damage on a target vessel due to proton beam-induced pressure waves is one of the crucial issues for the pulsed neutron source using a mercury spallation target. As a mitigation technique for the damage, the helium microbubble injection into the mercury has been carried out by using a swirl bubbler in order to utilize compressibility of bubbles. Moreover, double-walled structure, which consists of an outer wall and an inner wall, has been applied as the target head structure. In this study, we aim to develop an abnormality diagnostic technology to detect the inner wall cracking, which is caused by such cavitation damage, from the outside of the target vessel. The mercury flow fields in the case with the cracking are evaluated by computational fluid dynamics analysis based on finite element method. And then, effect of the cracking on the flow field is discussed from the point of view of the flow-induced vibration and the acoustic vibration.
Pacio, J.*; Van Tichelen, K.*; Eckert, S.*; Wondrak, T.*; Di Piazza, I.*; Lorusso, P.*; Tarantino, M.*; Daubner, M.*; Litfin, K.*; Ariyoshi, Gen; et al.
Nuclear Engineering and Design, 399, p.112010_1 - 112010_15, 2022/12
Times Cited Count：5 Percentile：84.97(Nuclear Science & Technology)Heavy-liquid metals (HLMs), such as lead and lead-bismuth eutectic (LBE), are proposed as primary coolants in accelerator driven systems and next-generation fast reactors. In Europe, the reference systems using HLMs are MYRRHA (LBE) and ALFRED (lead). This article presents an overview of recent experiences and ongoing activities on pool-type and loop-type HLM experiments. Pool tests include the measurement of forced- and natural-circulation flow patterns in several scenarios representative of nominal and decay heat removal conditions. Loop tests are focused on the evaluation of specific components, like mockups of the fuel assembly, control rod and heat exchangers. They involve the measurement of global variables, such as flow rate and pressure difference, and local quantities like temperature, velocity and vibrations. Advanced instrumentation, capable of sustaining high temperatures and corrosion, is necessary for accurate measurements, often in compact geometries. In addition to traditional techniques, other instrumentation based on optical fibers, ultrasonic and electromagnetic methods are discussed.
Ariyoshi, Gen; Obayashi, Hironari; Sasa, Toshinobu
Journal of Nuclear Science and Technology, 59(9), p.1071 - 1088, 2022/09
Times Cited Count：1 Percentile：31.61(Nuclear Science & Technology)Electromagnetic induction method is one of the effective techniques for local velocity measurement in heavy liquid metals. Ricou and Vives' probe and Von Weissenfluh's probe are famous instrumentations using a permanent magnet. However, sensitivity and measurement volume of the probes show unexpected variation since demagnetization of the magnet is occurred by temperature increase up to the Curie temperature. In this study, electromagnetic probe incorporating a miniature electromagnet was newly developed to overcome such unexpected variation. The diameter and the length of the sensor was 6 mm and 155 mm, respectively. The sensitivity and the measurement volume of the probe were assessed by measurement of local velocity of flowing mercury in a square channel. To clarify the validity for the measured velocity profiles, numerical velocity profiles were calculated and compared with experiment. And the validity for the measured velocity profiles were confirmed by calculated result.
Obayashi, Hironari; Yamaki, Kenichi*; Kita, Satoshi*; Ariyoshi, Gen; Sasa, Toshinobu
Proceedings of 19th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-19) (Internet), 11 Pages, 2022/03
JAEA developed a non-contact type flowmeter that two ultrasonic sensors were installed on outer surface of a cylindrical-shaped test section. The considerable issue of the realization was multiple reflection of emitted signal in the piping. Furthermore, wettability between LBE and inner surface of the test section was one of the important issue on the ultrasonic technique. To mitigate the multiple reflection, a critical angle as an incident angle not to produce a longitudinal wave on the solid / solid boundary was applied. And fine mirror-finished treatment was applied to the inner surface of the test section to ensure wettability. As a result of experiment at 350 degrees C, the observed correlation value between the non-contact type and the established plug type was 0.9986. Additionally, the developed non-contact type provided its sufficiently stable output during a long-term test more than 1,500 hours.
Ariyoshi, Gen; Obayashi, Hironari; Saito, Shigeru; Sasa, Toshinobu
Proceedings of 19th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-19) (Internet), 10 Pages, 2022/03
To clarify the flow characteristics of heavy liquid-metal (HLM) is important to achieve the construction of nuclear transmutation facility that utilizes HLM as a spallation target and coolant. At present, lead-bismuth eutectic (LBE) spallation target plans to be installed in Japan proton accelerator research complex (J-PARC). LBE is also selected as one of the candidate media of a spallation target and a coolant for innovative nuclear systems such as accelerator-driven system (ADS) and LBE-cooled fast reactor, due to its adequate physical/chemical properties. The characteristics of LBE flowing inside the target are usually clarified with computational fluid dynamics analysis since the measurement techniques for the HLM flow are not well established, especially for high temperature region over 450
C that is delivered from ADS's criteria. Therefore, the objective of this study is to develop measurement method for flow characteristics in the high temperature LBE. A miniature electro-magnet is introduced to electro-magnetic probe to overcome the limitation caused by a curie temperature of permanent magnet. To evaluate performance of the new probe, experimental apparatus equipping annular rotating vessel were also manufactured. The new probe was applied to high temperature LBE up to 480C. As a result, proportional induced voltage to the rotation speed of LBE were clearly observed, where excitation currents of the miniature electro-magnet were 0.2 A or 1 A. In this paper, configuration and performance of the newly developed electro-magnet probe to the high temperature LBE will be presented.
Ariyoshi, Gen; Ito, Daisuke*; Ito, Kei*; Saito, Yasushi*
JPS Conference Proceedings (Internet), 33, p.011044_1 - 011044_6, 2021/03
Sasa, Toshinobu; Saito, Shigeru; Obayashi, Hironari; Ariyoshi, Gen
JPS Conference Proceedings (Internet), 33, p.011051_1 - 011051_6, 2021/03
To realize Accelerator-driven system (ADS) for minor actinide transmutation, JAEA proposes to construct the Proton Irradiation Facility in J-PARC. The facility is planned to solve technical issues for safe application of Lead-bismuth Eutectic Alloy (LBE). The 250 kW LBE spallation target will be located in the facility to prepare material irradiation database by both proton and neutron irradiation in the temperature range for typical LBE-cooled ADS. Various studies for important technologies required to build the facilities are investigated such as oxygen concentration control, instruments development, remote handling techniques for target maintenance, and spallation target design. The large scale LBE loops for mock up the 250 kW LBE spallation target and material corrosion studies are also manufactured and applied to various experiments. The latest status of 250 kW LBE spallation target design works will be summarized.
Yamaki, Kenichi*; Kita, Satoshi*; Obayashi, Hironari; Ariyoshi, Gen; Saito, Shigeru; Sasa, Toshinobu
JAEA-Technology 2020-021, 26 Pages, 2021/02
JAEA-Technology-2020-021.pdf:2.34MB
As digitalization of measuring instruments, Programmable Logic Controller is mainly used for controlling large-scale devices, and many test devices are controlled in digital. Together with increase of the data storage capacity, it has become possible to record the measured values over the entire experimental period. By collecting the entire experimental data, it became easy to appropriately record the test environment during the corrosion test of materials and to analyze the changes and transients during continuous operation from various viewpoints. On the other hand, in a long-term test, the large number of measurement data were recorded, which requires long time for data processing and data extraction for analyses. In addition, it is necessary to pay attention to organize the data collected by different data formats. To solve these problems, a processing tool were produced to extract and process the data efficiently from the sequencer installed in the lead-bismuth test device.
Sasa, Toshinobu; Saito, Shigeru; Obayashi, Hironari; Ariyoshi, Gen; Wan, T.*; Okubo, Nariaki; Ohdaira, Naoya*; Yamaki, Kenichi*; Kita, Satoshi*; Yoshimoto, Hidemitsu*
no journal, ,
Japan Atomic Energy Agency (JAEA) proposes to reduce the minor actinides by Partitioning and Transmutation Technology using Accelerator-driven system (ADS). To realize ADS, JAEA plans to locate Lead-Bismuth Eutectic alloy (LBE) spallation target in J-PARC. LBE spallation target will be used to solve technical issues for ADS design by preparing irradiation database. The 400 MeV - 250 kW proton beam can be used for ADS studies. The spallation target is optimized by thermal-hydraulic analysis and structural analysis to increase proton/neutron irradiation of ADS materials by sharply focused proton beam injection. The studies for elemental technologies such as a fully-remote target exchange procedure and freeze-sealed drain valve system are also performed and integrated into the design of LBE target. The latest design of the J-PARC LBE spallation target system will be presented.
Kogawa, Hiroyuki; Kawashima, Hiroyuki; Ariyoshi, Gen; Wakui, Takashi; Saruta, Koichi; Naoe, Takashi; Haga, Katsuhiro; Futakawa, Masatoshi; Soyama, Hitoshi*; Kuji, Chieko*; et al.
no journal, ,
In a mercury target system of the J-PARC, an operation injecting microbubbles of helium gas into mercury is carried out to reduce the pressure waves that cause cavitation damage. It was confirmed the damage was mitigated by increasing the injection amount of gas bubbles, while the damage considered to be caused by impact pressure from the gas bubbles was observed. To improve durability, it is necessary to find the optimum bubble condition, and those are also important to evaluate the radiation damage of the vessel material and to develop a diagnosis technology. In this report, as the first report of the series, the outline of the development to improve the durability will be reported with the damage observation results.
Ariyoshi, Gen; Ito, Kei*; Kogawa, Hiroyuki; Futakawa, Masatoshi
no journal, ,
Cavitation damage caused by pressure waves is one of the important issues which threaten the integrity of the mercury spallation target vessel in J-PARC. To mitigate the damage, technology using mercury-helium two-phase flow has been developed. Although effective bubble radius for absorption/attenuation of the waves is evaluated as less than 0.1 mm, actual bubble radius might be different from the evaluated one due to microbubble coalescence phenomena. Therefore, the purpose of present study is to clarify and predict the bubble radius distribution in the target. To achieve that, visualization of microbubble coalescence phenomena was performed by using air-water two-phase flow as a model flow. Obtained experimental results and numerical prediction code presently developed will be explained.
Ariyoshi, Gen; Obayashi, Hironari; Sasa, Toshinobu
no journal, ,
Ariyoshi, Gen; Obayashi, Hironari; Sasa, Toshinobu
no journal, ,
Maeno, Koki*; Ariyoshi, Gen; Tsutsui, Kihei*; Saruta, Koichi; Kogawa, Hiroyuki; Li, Y.*; Futakawa, Masatoshi
no journal, ,
Cavitation damage is one of the issues for the mercury spallation target, which threatens the structural integrities of the target vessel wall. To reduce such cavitation damages, Japan Atomic Energy Agency (JAEA) tried to prevent the cavitation bubble growth using the "flow effect". To arrange the environment for the use of the "flow effect", a narrow channel was newly installed by adding an inner wall to the mercury target head. Moreover, the microbubble injection technique to the mercury was also used to reduce the pressure waves which is one of the causes of the cavitation bubble formation. Consequently, the damage could be almost weakened. However, the damage on the inner wall can still be accumulated gradually during the practical target operation. Then, the inner wall might be penetrated by such damage accumulation: wall cracking might happen to the inner wall. Therefore, development of a diagnostic technology for such inner wall cracking should be important. So, the purpose of this study is to clarify the flow field in the target head with wall cracking conditions. Effect of the wall cracking on the flow field in the target head was investigated by CFD analysis. For simplicity, the flow channel near the target head was simulated as two-dimensional models. As the results, the continuous vortices shedding was recognized in the cases of any cracking conditions. And, pulsation flows in the narrow channel were observed in the cases of the cracking width larger than 4 mm.
Ariyoshi, Gen; Ito, Kei*; Kogawa, Hiroyuki; Futakawa, Masatoshi
no journal, ,
Cavitation damage caused by pressure waves is one of the important issues which threaten the integrity of the mercury spallation target vessel in J-PARC. To mitigate the damage, technology using mercury-helium two-phase flow has been developed. Although effective bubble radius for absorption/attenuation of the waves is evaluated as less than 0.1 mm, actual bubble radius might be different from the evaluated one due to microbubble coalescence phenomena. Therefore, the purpose of present study is to clarify and predict the bubble radius distribution in the target. To achieve that, visualization of microbubble coalescence phenomena was performed by using air-water two-phase flow as a model flow. Obtained experimental results and numerical prediction code presently developed will be explained.
Maeno, Koki*; Ariyoshi, Gen; Saruta, Koichi; Murata, Atsushi*; Kogawa, Hiroyuki; Tsutsui, Kihei*; Li, Y.*; Futakawa, Masatoshi
no journal, ,
no abstracts in English
Maeno, Koki*; Ariyoshi, Gen; Saruta, Koichi; Murata, Atsushi*; Kogawa, Hiroyuki; Li, Y.*; Tsutsui, Kihei*; Futakawa, Masatoshi
no journal, ,
no abstracts in English
