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Journal Articles

Experimental analysis on dynamics of liquid molecules adjacent to particles in nanofluids

Hashimoto, Shunsuke*; Nakajima, Kenji; Kikuchi, Tatsuya*; Kamazawa, Kazuya*; Shibata, Kaoru; Yamada, Takeshi*

Journal of Molecular Liquids, 342, p.117580_1 - 117580_8, 2021/11

 Times Cited Count:0

Quasi-elastic neutron scattering (QENS) and pulsed-field-gradient nuclear magnetic resonance (PFGNMR) analyses of a nanofluid composed of silicon dioxide (SiO$$_{2}$$) nanoparticles and a base fluid of ethylene glycol aqueous solution were performed. The aim was to elucidate the mechanism increase in the thermal conductivity of the nanofluid above its theoretical value. The obtained experimental results indicate that SiO$$_{2}$$ particles may decrease the self-diffusion coefficient of the liquid molecules in the ethylene glycol aqueous solution because of their highly restricted motion around these nanoparticles. At a constant temperature, the thermal conductivity increases as the self-diffusion coefficient of the liquid molecules decreases in the SiO$$_{2}$$ nanofluids.

JAEA Reports

Development of semantic survey map building system using semi-autonomous mobile robots for surveying of disaster area and gathering of information in nuclear power station (Contract research); FY2019 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Tokyo Polytechnic University*

JAEA-Review 2020-062, 47 Pages, 2021/01

JAEA-Review-2020-062.pdf:3.43MB

JAEA/CLADS had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project in FY2019. Among the adopted proposals in FY2018, this report summarizes the research results of the "Development of Semantic Survey Map Building System using Semi-autonomous Mobile Robots for Surveying of Disaster Area and Gathering of Information in Nuclear Power Station" conducted in FY2019.

Journal Articles

Online measurement of the atmosphere around geopolymers under gamma irradiation

Cantarel, V.; Lambertin, D.*; Labed, V.*; Yamagishi, Isao

Journal of Nuclear Science and Technology, 58(1), p.62 - 71, 2021/01

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

The gas production of wasteforms is a major safety concern for encapsulating active nuclear wastes. For geopolymers and cements, the H$$_{2}$$ produced by radiolytic processes is a key factor because of the large amount of water present in their porous structure. Herein, the gas composition evolution around geopolymers was monitored on line under $$^{60}$$Co gamma irradiation. Transient evolution of the hydrogen production yield was measured for samples with different formulations. The rate of its evolution and the final values are consistent with the presence of a chemical reaction of the pseudo-first order consuming hydrogen in the samples. The results show this phenomenon can significantly reduce the hydrogen source term of geopolymer wasteform provided their diffusion constant remains low. Lower hydrogen production rates and faster kinetics were observed with geopolymers formulations in which pore water pH was higher. Besides hydrogen production, a steady oxygen consumption was observed for all geopolymers samples. The oxygen consumption rates are proportional to the diffusion constants estimated in the modelization of hydrogen recombination by a pseudo first order reaction.

JAEA Reports

Development of semantic survey map building system using semi-autonomous mobile robots for surveying of disaster area and gathering of information in nuclear power station (Contract research); FY2018 center of world intelligence project for nuclear science/technology and human resource development

Collaborative Laboratories for Advanced Decommissioning Science; Tokyo Polytechnic University*

JAEA-Review 2019-022, 35 Pages, 2020/01

JAEA-Review-2019-022.pdf:2.71MB

CLADS, JAEA, had been conducting the Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development (hereafter referred to "the Project") in FY2018. The Project aims to contribute to solving problems in nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2018, this report summarizes the research results of the Development of Semantic Survey Map Building System Using Semi-autonomous Mobile Robots for Surveying of Disaster Area and Gathering of Information in Nuclear Power Station. The objective of the present study is to research and develop semi-autonomous mobile robot systems (multi-sensor fusion system, semantic simultaneous localization and mapping (SLAM), system for traversable-route learning and safe traversable-route presentation, etc.) that simply, safely, and rapidly make semantic survey maps including multiple information (air dose rate, temperature, obstacles, etc.). The system will be applied to the investigation of the situation inside the building of the nuclear power station where people cannot access at the time of disaster.

Journal Articles

Diffusion and sorption behavior of HTO, Cs, I and U in mortar

Akagi, Yosuke*; Kato, Hiroyasu*; Tachi, Yukio; Sakamoto, Hiroyuki*

Progress in Nuclear Science and Technology (Internet), 5, p.233 - 236, 2018/11

A large amount of radioactive contaminated concrete will be generated from the decommissioning in the Fukushima Dai-ichi Nuclear Power Plant (NPP). For developing the plans of decommissioning and waste management including decontamination and disposal, it is important to estimate radionuclides inventory and concentration distribution in the concrete materials. In this study, effective diffusivities (De) and distribution coefficients (Kd) of HTO, Cs, I and U in OPC mortar were measured by through-diffusion and batch sorption experiments. De values derived were in the sequence of HTO, I, Cs, U, implying that cation exclusion effects may be important mechanisms in OPC mortar. Kd values derived by batch tests were higher by more than one order of magnitude than the diffusion-derived Kd values, indicating that crushing of samples had a strong influence on sorption. Diffusion and sorption mechanisms in OPC mortar were evaluated to predict the penetration behavior of these radionuclides.

Journal Articles

Present status of manufacturing and R&Ds for the JT-60SA tokamak

Higashijima, Satoru; Kamada, Yutaka; Barabaschi, P.*; Shirai, Hiroshi; JT-60SA Team

Fusion Science and Technology, 68(2), p.259 - 266, 2015/09

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

Journal Articles

Study of corrosion rate of carbon steel in diluted artificial seawater under simulated irradiation condition

Komatsu, Atsushi; Tsukada, Takashi; Ueno, Fumiyoshi; Yamamoto, Masahiro

Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 4 Pages, 2015/05

Effect of oxygen and hydrogen peroxide on corrosion rate of carbon steel in diluted artificial seawater was investigated by electrochemical methods. Diffusion coefficient and thickness of diffusion layer for oxygen and hydrogen peroxide were measured to estimate the diffusion limiting current density. Corrosion tests of carbon steel were also conducted in diluted artificial seawater containing oxygen and/or hydrogen peroxide at 323K. The diffusion coefficient of hydrogen peroxide was about 0.8 times lower than that of oxygen, and the thickness of diffusion layer was almost equivalent between oxygen and hydrogen peroxide. Diffusion limiting current density of hydrogen peroxide was estimated to be 0.4 times lower than that of oxygen in the same concentration at 323K. Plot of corrosion rate with the addition of concentration of oxygen and 0.4 times concentration of hydrogen peroxide showed good correlation.

Journal Articles

Influence of blistering on deuterium retention in tungsten irradiated by high flux deuterium 10-100eV plasmas

Luo, G.; Shu, Wataru; Nishi, Masataka

Fusion Engineering and Design, 81(8-14), p.957 - 962, 2006/02

 Times Cited Count:60 Percentile:97.02(Nuclear Science & Technology)

The influence of blistering on deuterium retention in W was investigated using the newly established plasma generator with controllable incident energies ranging from 100 eV down to around 10 eV and incident flux of 1$$times$$10$$^{22}$$ D/m$$^{2}$$/s. The retention in the irradiated samples was measured using a thermal desorption spectrometer (TDS) at a ramping rate of 5 $$^{circ}$$C/s. The results indicate that only one peak appears in each spectrum, with the peak temperatures ranging from 500 until 850 $$^{circ}$$C, much higher than those from the trapping sites like vacancies, grain boundaries, dislocation loops, or impurities, implying probably a direct origin from the molecules existing inside blisters, voids/bubbles. Significant decrease in the retention at a certain incident fluence after blister appearance was observed and attributed to rupturing of the blisters, consistent with the limited size and increasing number of the blisters with increasing the incident fluence, as observed by means of SEM.

Journal Articles

Nuclear technology and potential ripple effect of superconducting magnets for fusion power plant

Nishimura, Arata*; Muroga, Takeo*; Takeuchi, Takao*; Nishitani, Takeo; Morioka, Atsuhiko

Fusion Engineering and Design, 81(8-14), p.1675 - 1681, 2006/02

 Times Cited Count:3 Percentile:25.6(Nuclear Science & Technology)

In a fusion reactor plant, a neutral beam injector (NBI) will be operated for a long time, and it will allow neutron streaming from NBI ports to outside of the plasma vacuum vessel. It requires the superconducting magnet to develop nuclear technology to produce stable magnetic field and to reduce activation of the magnet components. In this report, the back ground of the necessity and the contents of the nuclear technology of the superconducting magnets for fusion application are discussed and some typical investigation results are presented, which are the neutron irradiation effect on Nb$$_{3}$$Sn wire, the development of low activation superconducting wire, and the design concept to reduce nuclear heating and nuclear transformation by streaming. In addition, recent activities in high energy particle physics are introduced and potential ripple effect of the technology of the superconducting magnets is described briefly.

Journal Articles

Incident energy dependence of blistering at tungsten irradiated by low energy high flux deuterium plasma beams

Luo, G.; Shu, Wataru; Nishi, Masataka

Journal of Nuclear Materials, 347(1-2), p.111 - 117, 2005/12

 Times Cited Count:74 Percentile:98.03(Materials Science, Multidisciplinary)

Polycrystalline tungsten samples have been irradiated at room temperature by high flux (1$$times$$10$$^{22}$$ D/m$$^{2}$$/s) deuterium plasma beams with incident energies ranging 7 $$sim$$ 98 eV/D. Surface blistering occurred at all energies. The critical fluence for blistering $$Phi$$$$_{cr}$$ was found to increase with decreasing the incident energy. At energies $$<$$ 20 eV/D, $$Phi$$$$_{cr}$$ increased more rapidly. This energy dependence of $$Phi$$$$_{cr}$$ may be explained by a proposed model dealing with the oxide barrier to deuterium uptake into and release from the bulk W. At all energies, the blisters increased in their size and number with fluence within the corresponding low fluence ranges. However the size stopped increasing at certain fluences, while the number kept increasing within the experimental fluence range, which could be attributed to rupturing of blisters at a certain size of about 2$$mu$$m.

Journal Articles

Measurement of energetic charged particles produced in fusion materials with 14 MeV neutron irradiation

Ochiai, Kentaro; Kondo, Keitaro; Murata, Isao*; Miyamaru, Hiroyuki*; Kubota, Naoyoshi; Takahashi, Akito*; Nishitani, Takeo

Fusion Engineering and Design, 75-79, p.859 - 863, 2005/11

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

The Fusion Neutronics Source (FNS) of JAERI currently carries out the measurements of energetic charged particles emitted from fusion materials irradiated with a well-collimated 14 MeV neutron beam. At the beginning, the double differential cross section beryllium was measured. We have measured proton, triton and a particle emitted from a beryllium sample of 100 $$mu$$m in thickness.The a particle and triton were produced by $$^{9}$$Be(n,$$alpha$$)$$^{6}$$He, $$^{9}$$Be(n,2n)2$$alpha$$ and $$^{9}$$Be(n,t)$$^{7}$$Li reactions respectively. Measured total reaction rates from the counts of a particles and tritons were 2.7$$times$$10$$^{-24}$$ and 6$$times$$10$$^{-27}$$/atom/neutron, respectively, which were consistent with the calculated values from the nuclear data JENDL-3.2.

JAEA Reports

Report of Workshop on Energy; May 13, 2004, JAERI, Tokyo, Japan

Tsujimoto, Kazufumi; Nagai, Yasuki

JAERI-Review 2005-004, 208 Pages, 2005/03

JAERI-Review-2005-004.pdf:82.79MB

The Working Group on Energy (WG) was organized under International Union of Pure and Applied Physics (IUPAP). The WG has been considering problems on future energy supply and role of physics to solve the subjects. As one of activities of the WG, a Workshop on Energy was held on May 13, 2004 at Center for Promotion of Computational Science and Engineering, Japan Atomic Energy Research Institute (JAERI) in Tokyo hosted by IUPAP and co-hosted by JAERI and High Energy Accelerator Research Organization. The objectives of this workshop are to suggest active contributions of pure and applied physics field to the solution of the energy problem and to advance research and development (R&D) of future energy through the discussions about present status, problem and prospect of different energy development in the world and in Japan. This report records the summary of the Workshop and, abstracts and materials of 12 presentations. After the invited presentations about overview of energy problems in the world, in China and in Japan, R&D activities on the following four fields were presented; "Research and Development of New Energy", "Research and Development of Fusion Energy", "Prospect of Accelerator Driven System (ADS)", and "Hydrogen Production, Storage and Transportation".

Journal Articles

Intelligible seminor on fusion reactors, 3; Plasma heating system to generate high temperature fusion palsmas

Inoue, Takashi; Sakamoto, Keishi

Nihon Genshiryoku Gakkai-Shi, 47(2), p.120 - 127, 2005/02

no abstracts in English

Journal Articles

Intelligible seminor on fusion reactors, 1; Introduction to fusion reactors

Ueda, Yoshio*; Inoue, Takashi; Kurihara, Kenichi

Nihon Genshiryoku Gakkai-Shi, 46(12), p.845 - 852, 2004/12

no abstracts in English

Journal Articles

Integral benchmark experiments of the Japanese Evaluated Nuclear Data Library (JENDL)-3.3 for the fusion reactor design

Nishitani, Takeo; Ochiai, Kentaro; Maekawa, Fujio; Shibata, Keiichi; Wada, Masayuki*; Murata, Isao*

IAEA-CN-116/FT/P1-22 (CD-ROM), 8 Pages, 2004/11

no abstracts in English

Journal Articles

Application of the two-dimensional Newcomb problem to compute the stability matrix of external MHD modes in a tokamak

Aiba, Nobuyuki*; Tokuda, Shinji; Ishizawa, Tomoko*; Okamoto, Masao*

Plasma Physics and Controlled Fusion, 46(11), p.1699 - 1721, 2004/11

 Times Cited Count:2 Percentile:6.89(Physics, Fluids & Plasmas)

The theory of the Newcomb equation has been applied to low-n external modes in a tokamak and a method has been developed to compute the stability matrix that gives the change of plasma potential energy due to external modes in terms of the surface values of the perturbations. By using this method, the spectral properties of the ideal external modes has been elucidated, such as coupling between external modes and internal modes, and the difference of the stability properties between a normal shear tokamak and a reversed shear tokamak. These results will be also useful in the stability analysis of resistive wall modes.

Journal Articles

Ion species control in high flux deuterium plasma beams produced by a linear plasma generator

Luo, G.; Shu, Wataru; Nakamura, Hirofumi; Ohira, Shigeru; Nishi, Masataka

Review of Scientific Instruments, 75(11), p.4374 - 4378, 2004/11

 Times Cited Count:40 Percentile:85.39(Instruments & Instrumentation)

The ion species ratios in low energy high flux deuterium plasma beams formed in a linear plasma generator were measured by a quadrupole mass spectrometer. And the species control in the plasma generator was evaluated by changing the operational parameters like neutral pressure, arc current, and axial magnetic confinement to the plasma column. The measurements reveal that the lower pressures prefer to form more D$$^{+}$$ ions, and the medium magnetic confinement at the higher pressures results in production of more D$$_{2}$$$$^{+}$$, while the stronger confinement and /or larger arc current are helpful to D$$_{2}$$$$^{+}$$ conversion into D$$_{3}$$$$^{+}$$. Therefore, the ion species can be controlled by adjusting the operational parameters of the plasma generator. With suitable adjustment, we can easily achieve plasma beams highly enriched with a single species of D$$^{+}$$, D$$_{2}$$$$^{+}$$, or D$$_{3}$$$$^{+}$$, to a ratio over 80%. It has been found that the axial magnetic configuration played a significant role in the formation of D$$_{3}$$$$^{+}$$ within the experimental pressure range.

JAEA Reports

Study on system integration of robots Operated in nuclear fusion facility and nuclear power plant facilities

Oka, Kiyoshi

JAERI-Research 2004-009, 225 Pages, 2004/07

JAERI-Research-2004-009.pdf:47.47MB

In the present paper, I describe the necessary approaches and elemental technologies to solve the issues on the system integration of the typical robot systems for maintenance in the nuclear fusion facility and rescue in the accident of the nuclear power plant facilities. These robots work under the intense radiation condition and restricted space in place of human. In particular, I propose a new approach to realize the system integration of the robot for actual use from the viewpoints of not only the environmental and working conditions but also the restructure and optimization of the required elemental technologies with a well balance in the robot system. Based on the above approach, I have a contribution to realize the robot systems working under the actual conditions for maintenance in the nuclear fusion facility and rescue in the accident of the nuclear power plant facilities.

JAEA Reports

Characteristics of a low energy and high flux compact plasma source and preliminary results in studying surface modification of tungsten irradiated by the source

Luo, G.; Shu, Wataru; Nakamura, Hirofumi; Ohira, Shigeru; Hayashi, Takumi; Nishi, Masataka

JAERI-Tech 2004-031, 27 Pages, 2004/03

JAERI-Tech-2004-031.pdf:2.88MB

A plasma source has been constructed for investigating plasma-surface interactions in a tokamak. It is a compact device with a total length less than 1 m, compared to other existing facilities in the world. However, it can provide with stable plasma beams of low energy ($$sim$$100 eV) and high flux ($$sim$$10$$^{22}$$ /m$$^{2}$$/s), close to the predicted edge plasma conditions near the ITER divertor. This report presents mainly its configuration and its characteristics, including influence of filament, arc discharge, magnetic field, bias voltage parameters, and so on, on plasma beam being delivered towards the sample. Also shown are the results of preliminary experiments of blister formation on tungsten samples irradiated by a deuterium plasma beam generated with the source.

127 (Records 1-20 displayed on this page)