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Journal Articles

Research on hydrogen safety technology utilizing the automotive catalyst

Ono, Hitomi*; Takenaka, Keisuke*; Kita, Tomoaki*; Taniguchi, Masashi*; Matsumura, Daiju; Nishihata, Yasuo; Hino, Ryutaro; Reinecke, E.-A.*; Takase, Kazuyuki*; Tanaka, Hirohisa*

E-Journal of Advanced Maintenance (Internet), 11(1), p.40 - 45, 2019/05

JAEA Reports

Preliminary combustion analyses using OpenFOAM

Thwe, T. A.; Terada, Atsuhiko; Hino, Ryutaro

JAEA-Technology 2018-012, 45 Pages, 2019/01

JAEA-Technology-2018-012.pdf:4.34MB

Under long-term storage of nuclear wastes including low- and high-level wastes, hydrogen can be spontaneously generated from corrosion of metal wastes and container wall itself, and from radiolysis of water in the waste. For the sake of hydrogen safety and the risk reduction of environmental contamination, we have started to investigate the behavior and characteristics of hydrogen combustion and explosion in waste vessel. In this report, we performed numerical simulation to investigate the characteristics of methane combustion by applying OpenFOAM. For combustion scenario, FireFoam solver with LES frame was used. As the results, the average temperature increased when the container height and inlet size increased. The simulation of gas diffusion by FireFoam results showed that helium diffused faster than hydrogen and methane. By XiFoame solver, the simulation was performed to obtain flame propagation radius for hydrogen-air premixed flame.

Journal Articles

Numerical investigation on unstable behaviors of cellular premixed flames at low Lewis numbers based on the diffusive-thermal model and compressible Navier-Stokes equations

Thwe, T. A.; Kadowaki, Satoshi; Hino, Ryutaro

Journal of Thermal Science and Technology (Internet), 13(2), p.18-00457_1 - 18-00457_12, 2018/12

Two dimensional unsteady calculations of reactive flows were performed in large domain to investigate the unstable behaviors of cellular premixed flames at low Lewis numbers based on the diffusive-thermal (D-T) model and compressible Navier-Stokes (N-S) equations. The growth rates obtained by the compressible N-S equations were large and the unstable ranges were wide compared with those obtained by the D-T model equations. When the length of computational domain increased, the number of small cells separated from large cells of the cellular flame increased drastically. The stronger unstable behaviors and the larger average burning velocities were observed especially in the numerical results based on the compressible N-S equations. In addition, the fractal dimension obtained by the compressible N-S equations was larger than that by the D-T model equations. Moreover, we confirmed that the radiative heat loss promoted the instability of premixed flames at low Lewis numbers.

JAEA Reports

Handbook of advanced nuclear hydrogen safety (1st Edition)

Hino, Ryutaro; Takegami, Hiroaki; Yamazaki, Yukie; Ogawa, Toru

JAEA-Review 2016-038, 294 Pages, 2017/03

JAEA-Review-2016-038.pdf:11.08MB

In the aftermath of the Fukushima nuclear accident, safety measures against hydrogen in severe accident have been recognized as a serious technical problem in Japan. Therefore, efforts have begun to form a common knowledge base between nuclear engineers and experts on combustion and explosion, and to secure and improve future nuclear energy safety. As one of such activities, we have prepared the "Handbook of Advanced Nuclear Hydrogen Safety" under the Advanced Nuclear Hydrogen Safety Research Program funded by the Agency for Natural Resources and Energy of the Ministry of Economy, Trade and Industry. The concepts of the handbook are as follows: to show advanced nuclear hydrogen safety technologies that nuclear engineers should understand, to show hydrogen safety points to make combustion-explosion experts cooperate with nuclear engineers, to expand information on water radiolysis considering the situation from just after the Fukushima accidents and to the waste management necessary for decommissioning after the accident, etc.

Journal Articles

Progress report of Japanese simulation research projects using the high-performance computer system Helios in the International Fusion Energy Research Centre

Ishizawa, Akihiro*; Idomura, Yasuhiro; Imadera, Kenji*; Kasuya, Naohiro*; Kanno, Ryutaro*; Satake, Shinsuke*; Tatsuno, Tomoya*; Nakata, Motoki*; Nunami, Masanori*; Maeyama, Shinya*; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 92(3), p.157 - 210, 2016/03

The high-performance computer system Helios which is located at The Computational Simulation Centre (CSC) in The International Fusion Energy Research Centre (IFERC) started its operation in January 2012 under the Broader Approach (BA) agreement between Japan and the EU. The Helios system has been used for magnetised fusion related simulation studies in the EU and Japan and has kept high average usage rate. As a result, the Helios system has contributed to many research products in a wide range of research areas from core plasma physics to reactor material and reactor engineering. This project review gives a short catalogue of domestic simulation research projects. First, we outline the IFERC-CSC project. After that, shown are objectives of the research projects, numerical schemes used in simulation codes, obtained results and necessary computations in future.

Journal Articles

Development of hydrogen behavior simulation code system

Terada, Atsuhiko; Matsumoto, Masaaki*; Sugiyama, Hitoshi*; Kamiji, Yu; Hino, Ryutaro

Proceedings of 6th International Conference on Hydrogen Safety (ICHS 2015) (CD-ROM), 11 Pages, 2015/10

To improve the safety performance of the Nuclear Power Station, especially on the hydrogen safety under severe accident conditions, a simulation code system has been developed to analyze hydrogen behavior including diffusion, combustion, explosion and structural integrity evaluation. This developing system consists of CFD and FEM tools in order to support various hydrogen user groups consisting of students, researchers and engineers. Preliminary analytical results obtained with above mentioned tools, especially with open source codes including buoyancy turbulent model and condensation model, agreed well with the existing test data.

Journal Articles

Progress of divertor simulation research toward the realization of detached plasma using a large tandem mirror device

Nakashima, Yosuke*; Takeda, Hisahito*; Ichimura, Kazuya*; Hosoi, Katsuhiro*; Oki, Kensuke*; Sakamoto, Mizuki*; Hirata, Mafumi*; Ichimura, Makoto*; Ikezoe, Ryuya*; Imai, Tsuyoshi*; et al.

Journal of Nuclear Materials, 463, p.537 - 540, 2015/08

 Times Cited Count:15 Percentile:5.53(Materials Science, Multidisciplinary)

Journal Articles

Development of new type passive autocatalytic recombiner, 1; Experimental study on degradation of catalyst

Kamiji, Yu; Matsumura, Daiju; Taniguchi, Masashi*; Nishihata, Yasuo; Tanaka, Hirohisa*; Hirata, Shingo*; Hara, Mikiya; Hino, Ryutaro

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

In a severe accident at a nuclear power plant, a large amount of hydrogen can be released to primary containment vessel or reactor building. Passive autocatalytic recombiner (PAR) is one of the most effective systems for hydrogen mitigation and safety accident management. The new type PAR is under developing to improve conventional PARs, especially its size and weight. In this study, the influence of steam coexistence for the automotive catalyst activity was experimentally examined. These results show that the steam slightly affects the reaction start up and catalyst activity.

Journal Articles

Development of hydrogen behavior simulation code system; Outline of code system and validation using existing data

Terada, Atsuhiko; Matsumoto, Masaaki*; Sugiyama, Hitoshi*; Kamiji, Yu; Kadowaki, Satoshi*; Hino, Ryutaro

Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 6 Pages, 2015/05

In the Fukushima Daiichi Nuclear Power Station (NPS) accident, hydrogen was generated by oxidation reaction of the cladding and water etc, then leaked into the NPS building, and finally led to occurrence of hydrogen explosion in the building. This resulted in serious damage to the environment. To improve the safety performance of the NPS, especially on the hydrogen safety under severe accident conditions, a simulation code system has been developed to analyze hydrogen behaviors including diffusion, combustion, explosion and structural integrity evaluation. This developing system consists of CFD and FEM tools in order to support various hydrogen user groups of students, researchers and engineers. Preliminary calculated results obtained with above mentioned tools, damage of piping induced by hydrogen combustion, agreed well with existing test data.

Journal Articles

Cosmic-ray muon radiography for reactor core observation

Takamatsu, Kuniyoshi; Takegami, Hiroaki; Ito, Chikara; Suzuki, Keiichi*; Onuma, Hiroshi*; Hino, Ryutaro; Okumura, Tadahiko*

Annals of Nuclear Energy, 78, p.166 - 175, 2015/04

 Times Cited Count:3 Percentile:53.75(Nuclear Science & Technology)

In our study, we focused on a nondestructive inspection method by which cosmic-ray muons could be used to observe the internal reactor from outside the RPV and the CV. We conducted an observation test on the HTTR to evaluate the applicability of the method to the internal visualization of a reactor. We also analytically evaluated the resolution of existing muon telescopes to assess their suitability for the HTTR observation, and were able to detect the major structures of the HTTR based on the distribution of the surface densities calculated from the coincidences measured by the telescopes. Our findings suggested that existing muon telescopes could be used for muon observation of the internal reactor from outside the RPV and CV.

Journal Articles

Development of new type passive autocatalytic recombiner, 1; Characterization of monolithic catalyst

Kamiji, Yu; Taniguchi, Masashi*; Nishihata, Yasuo; Nagaishi, Ryuji; Tanaka, Hirohisa*; Hirata, Shingo*; Hara, Mikiya; Hino, Ryutaro

Proceedings of 2nd International Conference on Maintenance Science and Technology (ICMST-Kobe 2014), p.87 - 88, 2014/11

For hydrogen mitigation, a new type passive autocatalytic recombiner is under development. In this study, the activation energy of hydrogen-oxygen recombination reaction was examined to clarify the basic characteristics of the catalyst. In addition, the degradation of the catalyst by $$gamma$$-ray irradiation simulating the environmental condition in nuclear power plants was also examined. As a result, the activation energy was experimentally estimated at 5.75 kJ/mol. Besides, no significant differences were observed in the compositional distribution from the EPMA results between the non-irradiated and the irradiated catalyst. However, the irradiated catalyst showed much more activity because of larger specific surface area of the catalyst and surface area of the precious metals. It showed that $$gamma$$-ray irradiation up to 1.0 MGy can increase activity of the catalyst.

Journal Articles

Numerical analysis of air-hydrogen mixture flow in rectangular indoor space with ventilators

Sugiyama, Hitoshi*; Takahashi, Keita*; Kato, Naoto*; Terada, Atsuhiko; Kamiji, Yu; Hino, Ryutaro

Jidosha Gijutsukai Gakujutsu Koenkai Zensatsushu, (109-14), p.5 - 10, 2014/10

Numerical analysis has been performed for vertical buoyant flow of air-hydrogen mixture in rectangular indoor space with ventilators. The unsteady and laminar flow has been calculated by using the coupled conservation equations of hydrogen and momentum. Calculated results are compared with the experiment data of hydrogen concentration and velocity profile in order to confirm the validity of the presented numerical method and clarify the mechanism of hydrogen dispersion. Although agreement is certainly not perfect in all detail, the main features are reasonably reproduced. Adding to this, calculated results suggest that hydrogen concentration depends on Froude number.

Journal Articles

Numerical analysis of turbulent flow in a rectangular duct containing straight cylinder placed near a bottom wall

Sugiyama, Hitoshi*; Otemori, Toshiki*; Kato, Naoto*; Terada, Atsuhiko; Kamiji, Yu; Hino, Ryutaro

Jidosha Gijutsukai Gakujutsu Koenkai Zensatsushu, (147-14), p.25 - 30, 2014/10

Numerical analysis has been performed for three-dimensional developing turbulent flow in a rectangular duct containing straight cylinder placed near a bottom wall. In this kind of turbulent flow, it has been pointed out as a characteristic features that anisotropic turbulence generates the secondary flow of the second kind and pulsation flow is measured in narrow gap region located between cylinder and bottom wall. Comparisons with the experimental results suggest that the present method is able to predict velocity profiles correctly and reproduce both the secondary flow of the second kind and the generation of pulsation flow near the narrow region between cylinder and bottom wall.

Journal Articles

Revaluation of hydrogen generation by water radiolysis in SDS vessels at TMI-2 accident

Nagaishi, Ryuji; Morita, Keisuke; Yamagishi, Isao; Hino, Ryutaro; Ogawa, Toru

Proceedings of 2014 Nuclear Plant Chemistry Conference (NPC 2014) (USB Flash Drive), 9 Pages, 2014/10

BB2014-1745.pdf:0.92MB

Two years after Three Mile Island Unit 2 (TMI-2) loss-of-coolant accident, radioactive contaminated water has been processed by Submerged Demineralizer System (SDS) with two types of zeolite adsorbents to remove radioactive nuclides. During and after the process, adsorption amount and distribution of nuclides on the zeolites, residual water content and thermal conductivity in the SDS vessels have been measured or estimated for verification of safety in the process, subsequent transportation and disposal. Hydrogen generation has been also evaluated mainly by direct monitoring in the large-scale of vessel after the process. In this work, the revaluation of hydrogen generation was demonstrated on the basis of the open information of vessel, and the latest experimental data obtained in adsorption and radiolysis occurring in small-scale of zeolite-water mixtures. As a result, the evaluated data was found to be comparable with the reported data obtained in the large-scale of real vessel.

Journal Articles

Consideration of radiolytic behavior in diluted and concentrated systems of seawater for computational simulation of hydrogen generation

Nagaishi, Ryuji; Inoue, Masao; Hino, Ryutaro; Ogawa, Toru

Proceedings of 2014 Nuclear Plant Chemistry Conference (NPC 2014) (USB Flash Drive), 9 Pages, 2014/10

Since seawater has been used as a coolant for reactors and spent fuel pools in broken reactor buildings at Fukushima Daiichi NPS accident, radioactive contaminated water emitted following the accident has contained salt content of seawater at high concentrations, different from that at TMI-2 accident. Radiolysis of seawater leading to hydrogen generation and corrosion has been simulated and reported by several groups. However, the proposed radiolysis models cannot be always applied to water radiolysis at the wide range of salt concentrations present in the NPS, mainly because primary yields of radiolysis products of water and radiation-induced reactions are dependent on the salt concentration. In this study, the radiolytic behavior in diluted and concentrated systems of seawater was considered on the basis of results in steady state and pulse radiolysis experiments, in which the above salt effects were demonstrated from the obtained results.

Journal Articles

Development of divertor simulation research in the GAMMA 10/PDX tandem mirror

Nakashima, Yosuke*; Sakamoto, Mizuki*; Yoshikawa, Masayuki*; Oki, Kensuke*; Takeda, Hisahito*; Ichimura, Kazuya*; Hosoi, Katsuhiro*; Hirata, Mafumi*; Ichimura, Makoto*; Ikezoe, Ryuya*; et al.

Proceedings of 25th IAEA Fusion Energy Conference (FEC 2014) (CD-ROM), 8 Pages, 2014/10

Journal Articles

Boiling heat transfer characteristics of a sulfuric-acid flow in thermochemical iodine-sulfur cycle

Noguchi, Hiroki; Terada, Atsuhiko; Onuki, Kaoru; Hino, Ryutaro

Chemical Engineering Research & Design, 92(9), p.1659 - 1663, 2014/09

 Times Cited Count:1 Percentile:91.22(Engineering, Chemical)

The Japan Atomic Energy Agency has been conducting research and development on the thermo-chemical iodine-sulfur (IS) process, which is one of the most attractive water-splitting hydrogen production methods that uses nuclear thermal energy. The sulfuric acid decomposer is one of the key components of the IS process. The boiling heat transfer coefficients of sulfuric acid solutions are required to design the sulfuric acid decomposer. These coefficients were measured in aqueous solutions where the mole fraction of H$$_{2}$$O ranged from 0.17 to 0.37 (heat flux range from 16.9 kW/m$$^{2}$$ to 5.6 kW/m$$^{2}$$) and compared with the empirical correlations formulated for binary mixtures. A combination of the Stephan-K$"o$rner correlation, using the empirical constant A$$_{0}$$ = 2.00, and the Nishikawa-Fujita correlation was used to predict the experimental results with an accuracy of 10%.

Journal Articles

Study of hydrogen mitigation for safe storage of spent cesium adsorption vessels

Kamiji, Yu; Terada, Atsuhiko; Okagaki, Yuria; Hino, Ryutaro

Journal of Nuclear Science and Technology, 51(7-8), p.964 - 967, 2014/07

 Percentile:100(Nuclear Science & Technology)

Hydrogen mitigation is one of the important issues for safe storage of spent cesium adsorption vessels at the Fukushima Daiichi NPS because the production and accumulation of hydrogen is induced by the radiolysis of residual water in the vessel. In the present study, an experimental examination was performed using a miniature acrylic vessel to simulate an upper section of the vessel using particle image velocimetry to clarify the internal flow and to verify the analytical results by the FLUENT code. As the result, weak upflow and circulating flow at the stepped section were successfully visualized, and the validity of the analytical results was confirmed by the flow patterns. Additionally, catalytic reaction test was conducted to evaluate its effectiveness. The results showed that the catalyst retains activity under the humid condition assumed in the real vessel.

Journal Articles

Characterization and storage of radioactive zeolite waste

Yamagishi, Isao; Nagaishi, Ryuji; Kato, Chiaki; Morita, Keisuke; Terada, Atsuhiko; Kamiji, Yu; Hino, Ryutaro; Sato, Hiroyuki; Nishihara, Kenji; Tsubata, Yasuhiro; et al.

Journal of Nuclear Science and Technology, 51(7-8), p.1044 - 1053, 2014/07

 Times Cited Count:4 Percentile:51.53(Nuclear Science & Technology)

For safe storage of zeolite wastes generated by treatment of radioactive saline water at the Fukushima Daiichi Nuclear Power Station, properties of the Herschelite adsorbent were studied and its adsorption vessel was evaluated for hydrogen production and corrosion. Hydrogen production depends on its water level and dissolved species because hydrogen is oxidized by radicals in water. It is possible to evaluate hydrogen production rate in Herschelite submerged in seawater or pure water by taking into account of the depth effect of the water. The reference vessel of decay heat 504 W with or without residual pure water was evaluated for the hydrogen concentration by thermal hydraulic analysis using obtained fundamental properties. Maximum hydrogen concentration was below the lower explosive limit (4 %). The steady-state corrosion potential of a stainless steel 316L increased with absorbed dose rate but its increase was repressed by the presence of Herschelite. At 750 Gy/h and $$<$$60$$^{circ}$$C which were values evaluated at the bottom of the vessel of 504 W, the localized corrosion of SUS316L contacted with Herschelite would not immediately occur under 20,000 ppm of Cl$$^{-}$$ concentration.

JAEA Reports

Study on long-term storage method for spent zeolite vessels; Establishment of code system for analyzing hydrogen diffusion, burning and explosion, and its impact

Terada, Atsuhiko; Takegami, Hiroaki; Kamiji, Yu; Hino, Ryutaro

JAEA-Data/Code 2013-011, 53 Pages, 2014/03

JAEA-Data-Code-2013-011.pdf:4.29MB

In the accident of Fukushima Daiichi NPP, the high-level contaminated water processing system with zeolite vessel. is operating for treatment of contaminated water mixed with seawater. A spent KURION zeolite vessel is detached from the water processing system and brought to exclusive storage yards. Although water in the vessel is drained before storage, combustible hydrogen could be produced via radiolysis of water absorbed in the zeolite. An analytical code system available for hydrogen diffusion, burning and explosion, and its impact has been prepared in order to confirm a safe long-term storage method of the vessel. The code system consists of several analytical codes such as general-purpose CFD code FLUENT, deflagration analytical code FLACS and detonation analytical code AUTODYN and interfaces connecting each code. This report presents an outline of analytical code system including interfaces, and introduces preliminary analytical study.

288 (Records 1-20 displayed on this page)