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Mikami, Nao*; Ueki, Yoshitaka*; Shibahara, Masahiko*; Aizawa, Kosuke; Ara, Kuniaki*
International Journal of Multiphase Flow, 171, p.104688_1 - 104688_13, 2024/01
Times Cited Count：0 Percentile：0(Mechanics)Mikami, Nao*; Ueki, Yoshitaka*; Shibahara, Masahiko*; Aizawa, Kosuke; Ara, Kuniaki
Proceedings of 17th International Heat Transfer Conference (IHTC-17) (Internet), 9 Pages, 2023/08
Mikami, Nao*; Ueki, Yoshitaka*; Shibahara, Masahiko*; Aizawa, Kosuke; Ara, Kuniaki
Journal of Sound and Vibration, 561, p.117797_1 - 117797_14, 2023/05
Times Cited Count：1 Percentile：64.13(Acoustics)Ueki, Yoshitaka*; Hashimoto, Shunsaku*; Shibahara, Masahiko*; Aizawa, Kosuke; Ara, Kuniaki
Proceedings of 30th International Conference on Nuclear Engineering (ICONE30) (Internet), 5 Pages, 2023/05
Mikami, Nao*; Ueki, Yoshitaka*; Shibahara, Masahiko*; Aizawa, Kosuke; Ara, Kuniaki
International Journal of Multiphase Flow, 159, p.104340_1 - 104340_8, 2023/02
Times Cited Count：4 Percentile：57.18(Mechanics)This study covers the accidental generation of bubble jet flow caused by steam generator (SG) tubes damaging in sodium cooled fast reactors (SFRs). The main objective of this study is to develop a novel state sensing method of bubble jet flow based on acoustic recognition and deep learning. Prior to the application of this method to actual SFRs, we utilize air and water as simulant fluids in order to perform the proof of concept. This study is divided into three phases. The first phase is the acquisition and analysis of pipe flow sound and bubble jet flow sound, each of which simulates the normal and anomaly sound from SG tubes in SFRs. The second phase is the preprocessing of acoustic signals and feature extraction. The third phase is the building of deep learning models and performance evaluation. As a result, every of our proposed models could distinguish between pipe flow sound and bubble jet sound with an accuracy of almost 100.00%, and the best model could classify pipe flow sound and three types of bubble jet flow sound with an accuracy of 99.76%. This result suggests that the acoustic recognition with deep learning has great potential to sense the state of bubble jet flow in actual SFRs.
Ara, Kuniaki; Hirabayashi, Masaru*
CROSS T&T, (71), p.10 - 14, 2022/07
Development of hydrogen concentration monitors based on the application of ultrasonic technology applicable to severe accidents in nuclear reactor facilities was conducted. This paper introduces the principle and features of the application of ultrasonic technology. This paper introduces the principles and features of the ultrasonic application, and describes the performance (measurement accuracy, time response, etc.) and environmental resistance of the prototype as development results. In addition, the application of the developed technology would be introduced.
Hatakeyama, Nozomi*; Miura, Ryuji*; Miyamoto, Naoto*; Miyamoto, Akira*; Ara, Kuniaki; Shimoyama, Kazuhito; Kato, Atsushi; Yamamoto, Tomohiko
Journal of Computer Chemistry, Japan, 21(2), p.61 - 62, 2022/00
no abstracts in English
Aizawa, Kosuke; Ara, Kuniaki; Hino, Ryutaro; Hirabayashi, Masaru*
Proceedings of OECD/NEA Specialist Workshop on Advanced Measurement Method and Instrumentation for enhancing Severe Accident Management in an NPP addressing Emergency, Stabilization and Long-term Recovery Phases (SAMMI 2020) (Internet), 4 Pages, 2020/12
Many functions of the instrumentation system did not work in the Tokyo Electric Power Company Fukushima Daiichi Nuclear Power Plant in the severe condition. The function of the hydrogen concentration measurement system was lost due to power supply loss and coolant loss because the system was based on the sampling method. Therefore, the development of an on-site installation type hydrogen monitor which is not based on the sampling method and has environment resistance characteristics is required. Thus, a new type of hydrogen monitor by using acoustic technique has been developed at JAEA. The measurement principle is to detect the changing of sound velocity with the hydrogen concentration in a mixed gas. In this paper, the basic performance and influence of environmental conditions are described.
Aizawa, Kosuke; Chikazawa, Yoshitaka; Ara, Kuniaki; Yui, Masahiro*; Jinno, Kentaro*; Hiramatsu, Takashi*
Proceedings of 2019 International Congress on Advances in Nuclear Power Plants (ICAPP 2019) (Internet), 7 Pages, 2019/05
Inspection technique in opaque liquid metal coolant is one of important issues for sodium-cooled fast reactors. Various under sodium viewers (USVs), including horizontal USVs for obstacle detection and imaging USVs, have been developed in several research institutes and countries. We aim practical realization of imaging USV which adopts an optical receiving system, which measures the vibration displacement of diaphragm by using a laser as a receiving sensor. This study mainly focuses on the sensitivity improvement of a receiving sensor. An issue for the sensitivity improvement of the receiving sensor is the sound pressure propagation inside the receiving sensor. Prototype tests in the water and sodium were conducted in order to resolve the issue. In addition, imaging experiments in the water and sodium were conducted using the improved receiving sensor. From the results of imaging experiments, the relation between obtained wave profile and the regeneration imaging was confirmed.
Kudo, Hideyuki*; Otani, Yuichi*; Hara, Masahide*; Kato, Atsushi; Ishikawa, Nobuyuki; Otaka, Masahiko; Nagai, Keiichi; Saito, Junichi; Ara, Kuniaki; Ide, Akihiro*
Proceedings of 2019 International Congress on Advances in Nuclear Power Plants (ICAPP 2019) (Internet), 10 Pages, 2019/05
A next generation SFR in Japan has adopted an advanced dry cleaning system which consists of the argon gas blowing process to reduce the amount of metallic residual sodium remaining on spent fuel assemblies. This paper describes experimental and analytical work focusing on the amount of residual sodium remaining on a fuel pin bundle before and after the argon gas blowing process. The experiments were conducted using a sodium test loop and a short specimen consisting of a 7 pin bundle. The effects of the blowing gas velocity and the blowing time were quantitatively analyzed in the experiments. On the basis of these experimental results, evaluation models predicting the amount of the residual sodium were constructed.
Ide, Akihiro*; Kudo, Hideyuki*; Inuzuka, Taisuke*; Hara, Masahide*; Kato, Atsushi; Ishikawa, Nobuyuki; Otaka, Masahiko; Nagai, Keiichi; Saito, Junichi; Ara, Kuniaki
Proceedings of 2019 International Congress on Advances in Nuclear Power Plants (ICAPP 2019) (Internet), 10 Pages, 2019/05
A next generation SFR in Japan has adopted an advanced dry cleaning system which consists of the following process of argon gas blowing to reduce the amount of metallic sodium, moist argon gas blowing to deactivate the residual sodium, and direct storage in the SFP without using storage containers. This three-step process increases economic competitiveness and reduces waste products. In this Research and Development work, the amount of residual sodium and performance of the dry cleaning process were investigated. This paper describes experimental and analytical work for all parts of a fuel assembly except for a fuel pin bundle.
Ichikawa, Kenta*; Kanda, Hironori; Yoshioka, Naoki*; Ara, Kuniaki; Saito, Junichi; Nagai, Keiichi
Proceedings of 26th International Conference on Nuclear Engineering (ICONE-26) (Internet), 6 Pages, 2018/07
Studies on the suppression of the reactivity of sodium itself have been performed on the basis of the concept of suspended nanoparticles in liquid sodium (sodium nanofluid). According to the experimental and theoretical results of studies for sodium nanofluid, velocity and heat of sodium nanofluid-water reaction are lower than those of the pure sodium-water reaction. The analytical model for the peak temperature of a sodium nanofluid-water reaction jet has been developed in consideration of these suppression effects by the authors. In this paper, the prediction method for mitigation effects for a damage of adjacent tubes in a steam generator tube rupture (SGTR) accidents is arranged by applying this analytical model for the peak temperature of the reaction jet. On the assumption that the sodium nanofluid is used for the secondary coolant of sodium-cooled fast reactor (SFR), mitigation effects under the design-base accident (DBA) condition and the design-extension condition (DEC) of SGTR are estimated by using this method. As a result, there is a possibility to reduce the number of damaged tubes and to suppress the pressure generated by SGTR accidents by using sodium nanofluid in the secondary coolant.
Obayashi, Hironari; Hirabayashi, Masaru; Sasa, Toshinobu; Ara, Kuniaki
NEA/CSNI/R(2017)2 (Internet), p.188 - 194, 2017/06
no abstracts in English
Aizawa, Kosuke; Chikazawa, Yoshitaka; Ara, Kuniaki; Yui, Masahiro*; Uemoto, Yohei*; Kurokawa, Masaaki*; Hiramatsu, Takashi*
Proceedings of International Conference on Fast Reactors and Related Fuel Cycles; Next Generation Nuclear Systems for Sustainable Development (FR-17) (USB Flash Drive), 9 Pages, 2017/06
Inspection in opaque liquid metal coolant is one of important issues for sodium-cooled fast reactors. To facilitate operations and maintenance activities, various under sodium viewers (USVs), including horizontal USVs for obstacle detection for a long distance and imaging USVs for a short and middle distance imaging, have been developed in several research institutes and countries. In this study, an imaging USV for a middle distance, approximately 1 m, has been developed. The USV in this study adopts an optical receiving system which measures the vibration displacement of diaphragm by using a laser as a receiving sensor. This study mainly focuses on the sensitivity improvement for a transmission sensor and the receiving sensor. In addition, an imaging experiment in the water was conducted using the new transmission sensor and receiving sensor. The experimental results showed that the newly developed USV sensors can make higher resolution images of a target than the previous sensors.
Kato, Atsushi; Nagai, Keiichi; Ara, Kuniaki; Otaka, Masahiko; Oka, Nobuki*; Tanaka, Masako*; Otani, Yuichi*; Ide, Akihiro*
Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 8 Pages, 2017/04
In a fuel handling system (FHS) of a sodium-cooled fast reactor, it is necessary to reduce residual sodium on a spent fuel subassembly before storing at a spent fuel water-pool (SFP) in order to minimize design loads. Although the wet cleaning process adopted on MONJU could eliminate almost all of residual sodium, a large amount of radioactive liquid waste occurs and it needs long duration of cleaning treatment and large plant commodities. On the other hand, Japan sodium-cooled fast reactor adopted an advanced dry cleaning system which consists of roughly blowing massive sodium on the fuel subassembly out by 300
C argon gas, inactivation of residual sodium to NaOH by moist argon gas and directly immersion into the SFP to achieve economic competitiveness and waste reduction. This paper reports current status of recent R&D activities to demonstrate a performance of the dry cleaning process in Japan which are for improvement of the cleaning performance and optimizing the FHS design.
Obayashi, Hironari; Hirabayashi, Masaru; Sasa, Toshinobu; Ara, Kuniaki
Proceedings of 11th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, Operation and Safety (NUTHOS-11) (USB Flash Drive), 10 Pages, 2016/10
Itami, Toshio*; Saito, Junichi; Ara, Kuniaki
Metals, 5(3), p.1212 - 1240, 2015/09
Times Cited Count：2 Percentile：4.14(Materials Science, Multidisciplinary)A new kind of suspension liquid was developed by dispersing Ti nanoparticles (10 nm) in liquid Na, which was then determined by TEM (transmission electron microscopy) analysis. The volume fraction was estimated to be 0.0088 from the analyzed Ti concentration (2 at.%) and the densities of Ti and Na. This suspension liquid, Liquid Sodium containing nanoparticles of titanium (LSnanop), shows, despite only a small addition of Ti nanoparticles, many striking features, namely a negative deviation of 3.9% from the ideal solution for the atomic volume, an increase of 17% in surface tension, a decrease of 11% for the reaction heat to water, and the suppression of chemical reactivity to water and oxygen. The decrease in reaction heat to water seems to be derived from the existence of excess cohesive energy of LSnanop. The excess cohesive energy was discussed based on simple theoretical analyses, with particular emphasis on the screening effect. The suppression of reactivity is discussed with the relation to the decrease of heat of reaction to water or the excess cohesive energy, surface tension, the action as a plug of Ti oxide, negative adsorption on the surface of LSnanop, and percolation.
Saito, Junichi; Itami, Toshio; Ara, Kuniaki
Journal of Nanoparticle Research, 14(12), p.1298_1 - 1298_17, 2012/12
Times Cited Count：4 Percentile：19.69(Chemistry, Multidisciplinary)Saito, Junichi; Ara, Kuniaki
Transactions of the American Nuclear Society, 107(1), p.433 - 436, 2012/11
no abstracts in English
Nishimura, Masahiro; Nagai, Keiichi; Onojima, Takamitsu; Saito, Junichi; Ara, Kuniaki; Sugiyama, Kenichiro*
Journal of Nuclear Science and Technology, 49(1), p.71 - 77, 2012/01
Times Cited Count：4 Percentile：31.96(Nuclear Science & Technology)Oxidation in the early stage of sodium combustion is especially important regarding the aspect of reaction continuity. The purpose of this study is to understand the sodium reaction precisely in order to apply the knowledge of the sodium reaction to promoting further safety of FRs.
