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JAEA Reports

Annual report for FY2018 on the activities of Naraha Center for Remote Control Technology Development (April 1, 2018 - March 31, 2019)

Hanari, Toshihide; Furukawahara, Ryo; Tsuchida, Yoshihiro; Kawabata, Kuniaki; Chiba, Yusuke

JAEA-Review 2019-047, 32 Pages, 2020/03

JAEA-Review-2019-047.pdf:2.45MB

Naraha Center for Remote Control Technology Development (Naraha Center) was established in Japan Atomic Energy Agency to promote a decommissioning work of Fukushima Daiichi Nuclear Power Station (Fukushima Daiichi NPS). Naraha Center consists of a Full-scale Mock-up Test Building and Research Management Building, and various test facilities are installed in them for the decommissioning work of Fukushima Daiichi NPS. The number of facility use in Naraha Center was 64 in FY2018. This report summarizes the activities of Naraha Center in FY2018, such as the utilization of facilities and equipment of Naraha Center, the development of remote control technologies for supporting the decommissioning work, maintenance of the remote control machines for emergency response, and training for operators by using the machines.

Journal Articles

Development of under sodium viewer for next generation sodium-cooled Fast reactor; Imaging test in sodium

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.

Journal Articles

Dry cleaning process test for fuel assembly of fast reactor plant system, 1; Pilot scale test for fuel pin bundle

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.

Journal Articles

Dry cleaning process test for fuel assembly of fast reactor plant system, 2; Laboratory scale test for fuel assembly and evaluation of the amount of residual sodium

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.

Journal Articles

Estimation of mitigation effects of sodium nanofluid for SGTR accidents in SFR

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.

Journal Articles

Development of an altitude-keeping system for underwater robots using laser beams

Takemura, Fumiaki*; Taba, Ryo*; Hirayama, Keita*; Tansuriyavong, S.*; Kawabata, Kuniaki; Sagara, Shinichi*; Ogasawara, Kei*

Artificial Life and Robotics, 22(4), p.405 - 411, 2017/12

The manta method is a survey method that divers investigate the degree of coral and whitening state while being towed to a boat. The manta method makes great physical burden. Therefore, the authors think that this task can substitute an underwater robot. This underwater robot is desirable to be able to keep altitude above the seabed. Hence, the authors have been developing the altitude (its distance above the sea floor) keeping system for an underwater robot. Visual recognition of distant underwater objects is possible in the water with high transparency, for example, in the coastal sea area of Okinawa prefecture, Japan. So, the authors have been adopting the distance measuring method using the two laser beams and a monocular camera with image processing. It realize to keep altitude of an underwater robot by using such devices. The evaluation experiments of the altitude keeping system are carried out in the pool.

Journal Articles

Application of ultrasonic flowmeter for LBE flow

Obayashi, Hironari; Hirabayashi, Masaru; Sasa, Toshinobu; Ara, Kuniaki

NEA/CSNI/R(2017)2 (Internet), p.188 - 194, 2017/06

no abstracts in English

Journal Articles

Development of under sodium viewer for next generation sodium-cooled fast reactors

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.

Journal Articles

Development of high-performance monitoring system under severe accident condition

Takeuchi, Tomoaki; Tsuchiya, Kunihiko; Komanome, Hirohisa*; Miura, Kuniaki*; Ishihara, Masahiro

Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 6 Pages, 2017/04

After the accident at the Fukushima Dai-ichi (1F) Nuclear Power Plant (NPP), the Japanese Government referred to "Enhancement of instrumentation to identify the status of the reactors and PCVs", in the report of Japanese government to the IAEA ministerial conference in June 2011. In response to these provisions, a research and development of a monitoring system for NPPs situations during severe accidents started in November 2012. The objectives of the R&D are composed of radiation-resistant monitoring camera, radiation-resistant in-water transmission system, and heat-resistant signal cable. For all the three objectives, the elemental technologies have been already developed and now trial system are being fabricated and tested under simulated conditions of severe accidents. The results will enable us to determine the basic specifications of the systems and to provide the information about application limits for users.

Journal Articles

Dry cleaning process test for fuel assembly of fast reactor plant system

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$$^{circ}$$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.

Journal Articles

Generation method of underwater landmarks for ocean observation

Takahashi, Satoru*; Nota, Yoshiki*; Matsuda, Asahi*; Kawabata, Kuniaki; Suzuki, Tsuyoshi*; Takemura, Fumiaki*; Ogasawara, Kei*; Kaneko, Shunichi*

Journal of Signal Processing, 21(1), p.15 - 24, 2017/01

In recent years, many researchers try to observe the state of the global environment from marine information for the understanding of the global environment change. First, we introduce the recording system of underwater environment which is made by the authors. By using this system, we want to observe the change of global environment from the coral bleaching. In this paper, especially, we propose the generation method of underwater landmark which is used to measure the position of robot of oceanographic observation based on the dynamic image processing. In here, underwater landmark means the feature point in underwater image.

Journal Articles

Development of plug-in type ultrasonic flowmeter for lead-bismuth spallation target system

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

Journal Articles

Status of R&D of high-performance monitoring system under sever accident

Tsuchiya, Kunihiko; Takeuchi, Tomoaki; Komanome, Hirohisa*; Miura, Kuniaki*; Araki, Masanori; Ishihara, Masahiro

Nippon Hozen Gakkai Dai-13-Kai Gakujutsu Koenkai Yoshishu, p.375 - 378, 2016/07

no abstracts in English

Journal Articles

Development of an altitude maintenance system for underwater robots using laser beams

Taba, Ryo*; Takemura, Fumiaki*; Tansuriyavong, S.*; Kawabata, Kuniaki; Sagara, Shinichi*; Ogasawara, Kei*

Proceedings of 21st International Symposium on Artificial Life and Robotics (AROB 21st 2016) and 1st International Symposium on BioComplexity (ISBC-1) (Internet), p.395 - 399, 2016/01

Journal Articles

The Promising features of new nano liquid metals; Liquid sodium containing titanium nanoparticles (LSnanop)

Itami, Toshio*; Saito, Junichi; Ara, Kuniaki

Metals, 5(3), p.1212 - 1240, 2015/09

 Times Cited Count:2 Percentile:90.24(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.

Journal Articles

The Preparation, physicochemical properties, and the cohesive energy of liquid sodium containing titanium nanoparticles

Saito, Junichi; Itami, Toshio; Ara, Kuniaki

Journal of Nanoparticle Research, 14(12), p.1298_1 - 1298_17, 2012/12

 Times Cited Count:4 Percentile:77.27(Chemistry, Multidisciplinary)

Journal Articles

Chemical reactivity suppression of liquid sodium by suspended nanoparticles

Saito, Junichi; Ara, Kuniaki

Transactions of the American Nuclear Society, 107(1), p.433 - 436, 2012/11

no abstracts in English

Journal Articles

Development of reactor water level sensor for extreme conditions

Miura, Kuniaki*; Shibata, Akira; Nakamura, Jinichi; Ogasawara, Toshihiko*; Saito, Takashi; Tsuchiya, Kunihiko

JAEA-Conf 2011-003, p.193 - 195, 2012/03

In the Fukushima accident, measurement failure of water level was one of the most important factors which caused this serious situation. The differential pressure type water level indicators are widely used in various place of nuclear plant but after the accident of TMI-2, the need of other reliable method has been demanded. And the BICOTH type and the TRICOTH type water level indicator for light water power reactors had been developed for in-pile water level indicator but currently those are not adopted to a nuclear power plant. In this study, the development of new type water level indicator which composed of thermocouple and heater, and the demonstration test and characteristic evaluation of the water level indicator were described.

Journal Articles

The Sodium oxidation reaction and suppression effect of sodium with suspended nanoparticles; Growth behavior of dendritic oxide during oxidation

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:3 Percentile:69.14(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.

Journal Articles

Eddy current-adjusted plasma shape reconstruction by Cauchy condition surface method on QUEST

Nakamura, Kazuo*; Jiang, Y.*; Liu, X.*; Mitarai, Osamu*; Kurihara, Kenichi; Kawamata, Yoichi; Sueoka, Michiharu; Hasegawa, Makoto*; Tokunaga, Kazutoshi*; Zushi, Hideki*; et al.

Fusion Engineering and Design, 86(6-8), p.1080 - 1084, 2011/10

 Times Cited Count:4 Percentile:61.89(Nuclear Science & Technology)

195 (Records 1-20 displayed on this page)