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JAEA Reports

Handbook of Advanced Nuclear Hydrogen Safety (2nd Edition); Development of hydrogen behavior integrated analysis system and application to actual PWR

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

JAEA-Review 2024-049, 400 Pages, 2025/03

JAEA-Review-2024-049.pdf:13.94MB

In the aftermath of the Fukushima Daiichi Nuclear Power Station accident, safety measures against hydrogen in severe accident has been recognized as a serious technical problem in Japan. As one of efforts to form a common knowledge base between nuclear engineers and experts on combustion and explosion, we issued the "Handbook of Advanced Nuclear Hydrogen Safety (1st edition)" in 2017. For improvement of the rational advancement of hydrogen safety measures and further reliability of hydrogen safety evaluation, a CFD analysis is highly expected to produce more precisely and quantitative results. We have been developing an integrated CFD analysis code system which can analyze hydrogen diffusion, explosion-combustion and structural integrity at the severe accident especially for pressurized water reactors (PWRs). We organized the role of LP and the CFD analyses and their utilization examples of hydrogen safety validation. Based on these results, we made the "Handbook of Advanced Nuclear Hydrogen Safety (2nd volume)". The analysis results of real scale PWR described in 2nd volume are confirmed by cross-analysis models and existing data obtained through representative small, medium and large-scale tests.

Journal Articles

Numerical simulation on dispersion of hydrogen leaked in particle layers of glass beads and soil

Terada, Atsuhiko; Nagaishi, Ryuji

Nuclear Technology, 210(10), p.1871 - 1887, 2024/10

 Times Cited Count:0 Percentile:0.00(Nuclear Science & Technology)

In order to understand dispersion of H2 leaked in packed beds of non-porous/porous particles in a partially open space practically, the dispersion of H2 in the particle layers of glass beads and soil was analytically studied using a CFD code to be compared with the experiments and to elucidate the effects of particle layer. H2 flowed out from a single leak point in the particle layer of non-porous glass beads was affected by buoyancy around the leak point, and diffused directly above the leak point in an elliptical shape faster than in the horizontal direction. After that, when it reached the air layer in the head space above the particle layer, H2 spread horizontally, formed a large concentration gradient near the boundary between the particle layer and the air layer, and further diffused in the air layer until the H2 concentration became about 1/3 or less of the concentration near the surface of particle layer. The calculations largely reproduced the experimental concentration distributions. When the particle layer was porous decomposed granite soil, the diffusion behavior of H2 in the particle layer proceeded in the same manner as in the case of glass beads. However, a large concentration gradient was formed near the boundary between the particle layer and the air layer, and then H2 diffused in the air layer until the H2 concentration became below the lower combustion limit. It was suggested through sensitivity analysis that the air permeability coefficient had a large effect on the time course of H2 concentration distribution. Based on the above, we further simulated H2 behavior in the vessel containing the H2 leaked particle layer. By inserting multiple vent pipes without considering H2 generation distribution and particle properties in the particle layer, H2 accumulated from one pipe was discharged by buoyancy without depending on the H2 generation distribution and particle properties in the particle layer, and air flowed in from the other pipe.

Journal Articles

Analytical studies on effects of wind on dispersion of hydrogen leaked in a partially open space

Terada, Atsuhiko; Nagaishi, Ryuji

Journal of Nuclear Science and Technology, 61(8), p.1135 - 1154, 2024/08

 Times Cited Count:0 Percentile:0.00(Nuclear Science & Technology)

In order to elucidate ventilation and exhaust of hydrogen leaked in a partially open space practically, the effects of outer wind on them were studied analytically by using a CFD code in the room of experimental Half-size Hallway model, which has a H$$_{2}$$ release hole on the bottom, one vent on the roof and another vent on the side: external air flowed in the room from the Door vent and then H$$_{2}$$ was discharged outside from the Roof vent. The H$$_{2}$$ concentration distribution in the room was divided into two layers at the height of Door vent, with a high concentration layer above it and a low concentration layer below it, forming a stratified interface. When the wind speed blown into the room increased, the combination of the Realizable k-e; turbulence model and the turbulence Schmidt number of 1.0 improved the reproducibility of the analysis results of H$$_{2}$$ concentration distribution. The trial analysis suggested that the concern that wind would increase the indoor H$$_{2}$$ concentration could be reduced by using the plate with a simple structure in which two plates were crossed on the Roof vent.

Journal Articles

Effects of vent size and wind on dispersion of hydrogen leaked in a partially open space; Studies by numerical analysis

Terada, Atsuhiko; Nagaishi, Ryuji

Nuclear Science and Engineering, 197(4), p.647 - 659, 2023/04

 Times Cited Count:3 Percentile:45.58(Nuclear Science & Technology)

In order to understand dispersion of hydrogen leaked in a partially open space practically, which can be considered as a basic model for all processes of transfer, treatment, storage and disposal of radioactive materials containing fuel debris in the decommissioning of nuclear facilities after a severe accident, by using a CFD code, the effects of vent size and outer wind on the H$$_{2}$$ dispersion were analytically studied by adopting the experimental Hallway model, which has H$$_{2}$$ release hole on the ceiling, one vent on the Roof vent and Door vent. Air flowed in the model from the Door vent, while H$$_{2}$$ was discharged outside from the Roof vent. The discharged amount of H$$_{2}$$ increased in conjunction with the air inflow when the size of Roof and or Door vents was increased. The effect of wind depended on the direction to the Door vent: wind from the same direction as the Door vent promoted the H$$_{2}$$ discharge, while wind from the opposite direction suppressed. The dispersion characteristics of indoor leaked H$$_{2}$$ was clarified for comparing model tests with the same Froude number and different scales. It was found from the analysis results of comparing model tests with the same Froude number and different scales that when the H$$_{2}$$ leaked into the room and diffused to the air, the flow generated by the buoyancy of mixed gas created the stack effect which caused the natural ventilation by drawing in the air from the outside through vent. In addition, it was speculated that the H$$_{2}$$ concentration decreased after its leak by quickly mixing with the air which flowed in from the vents and reached to the floor due to the Coanda effect, which is the effect of the free jet being drawn to a nearby wall.

Journal Articles

Simulation of the self-propagating hydrogen-air premixed flame in a closed-vessel by an open-source CFD code

Thwe Thwe, A.; Terada, Atsuhiko; Hino, Ryutaro; Nagaishi, Ryuji; Kadowaki, Satoshi

Journal of Nuclear Science and Technology, 59(5), p.573 - 579, 2022/05

 Times Cited Count:0 Percentile:0.00(Nuclear Science & Technology)

The simulations of the combustion of self-propagating hydrogen-air premixed flame are performed by an open-source CFD code. The flame propagation behavior, flame radius, temperature and pressure are analyzed by varying the initial laminar flame speed and grid size. When the initial laminar speed increases, the thermal expansion effects become strong which leads the increase of flame radius along with the increase of flame surface area, flame temperature and pressure. A new laminar flame speed model derived previously from the results of experiment is also introduced to the code and the obtained flame radii are compared with those from the experiments. The formation of cellular flame fronts is captured by simulation and the cell separation on the flame surface vividly appears when the gird resolution becomes sufficiently higher. The propagation behavior of cellular flame front and the flame radius obtained from the simulations have the reasonable agreement with the previous experiments.

Journal Articles

Enrichment of chalcophile elements in seawater accompanying the end-Cretaceous impact event

Maruoka, Teruyuki*; Nishio, Yoshiro*; Kogiso, Tetsu*; Suzuki, Katsuhiko*; Osawa, Takahito; Hatsukawa, Yuichi*; Terada, Yasuko*

GSA Bulletin, 132(9-10), p.2055 - 2066, 2020/09

 Times Cited Count:2 Percentile:9.79(Geosciences, Multidisciplinary)

Journal Articles

Establishment of reasonable 2-D model to investigate heat transfer and flow characteristics by using scale model of vessel cooling system for HTTR

Takada, Shoji; Ngarayana, I. W.*; Nakatsuru, Yukihiro*; Terada, Atsuhiko; Murakami, Kenta*; Sawa, Kazuhiro*

Mechanical Engineering Journal (Internet), 7(3), p.19-00536_1 - 19-00536_12, 2020/06

In this study reasonable 2D model was established by using FLUENT for start-up of analysis and evaluation of heat transfer flow characteristics in 1/6 scale model of VCS for HTTR. By setting up pressure vessel temperature around 200$$^{circ}$$C about relatively high ratio of heat transfer via natural convection in total heat removal around 20-30%, which is useful for code to experiment benchmark in the aspect to confirm accuracy to predict temperature distribution of components which is heated up by natural convection flow. The numerical results of upper head of pressure vessel by the $$kappa$$-$$omega$$-SST intermittency transition model, which can adequately reproduce the separation, re-adhesion and transition, reproduced the test results including temperature distribution well in contrast to those by the $$kappa$$-$$varepsilon$$ model in both cases that helium gas is evacuated or filled in the pressure vessel. It was emerged that any local hot spot did not appear on the top of upper head of pressure vessel where natural convection flow of air is separated in both cases. In addition, the plume of high temperature helium gas generated by the heating of heater was well mixed in the upper head and uniformly heated the inner surface of upper head without generating hot spots.

Journal Articles

Development of strength evaluation method of ceramic reactor for iodine-sulfur process and hydrogen production test in Japan Atomic Energy Agency

Takegami, Hiroaki; Noguchi, Hiroki; Tanaka, Nobuyuki; Iwatsuki, Jin; Kamiji, Yu; Kasahara, Seiji; Imai, Yoshiyuki; Terada, Atsuhiko; Kubo, Shinji

Nuclear Engineering and Design, 360, p.110498_1 - 110498_6, 2020/04

 Times Cited Count:16 Percentile:84.86(Nuclear Science & Technology)

Japan Atomic Energy Agency (JAEA) has been conducting R&D on the thermochemical iodine-sulfur (IS) process for nuclear-powered hydrogen production. The IS process is one of the promising candidates of heat application of the high-temperature gas-cooled reactors. JAEA fabricated main chemical reactors made of industrial structural materials and confirmed their integrity in practical corrosive environments in the IS process. Based on the results of these confirmation tests, JAEA have constructed a 100 NL/h-H$$_{2}$$-scale test facility made of industrial structural materials. In this report, we succeeded in extending the hydrogen production time from 8 hours to 31 hours by developing a stable hydrogen iodide solution transfer technology in a continuous hydrogen production test. In addition, using the fracture test data of the ceramic specimen, an equation for estimating the strength of the ceramic component was developed.

Journal Articles

Establishment of numerical model to investigate heat transfer and flow characteristics by using scale model of vessel cooling system for HTTR

Takada, Shoji; Ngarayana, I. W.*; Nakatsuru, Yukihiro*; Terada, Atsuhiko; Murakami, Kenta*; Sawa, Kazuhiko*

Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 13 Pages, 2019/05

In the loss of core cooling test using HTTR, a technical issue is to improve prediction accuracy of temperature distribution of components in vessel cooling system (VCS). An establishment of reasonable 2D model was started by using numerical code FLUENT, which was validated using the test data by 1/6 scale model of VCS for HTTR. The pressure vessel (PV) temperature was set around 200$$^{circ}$$C attributed to relatively high ratio of natural convection heat transfer around 20% in total heat removal, which is useful for code to experiment benchmark to improve prediction accuracy. It is necessary to confirm heat transfer flow characteristics around the top of PV which is heated up by natural convection flow which was considered to be affected by separation, re-adhesion and transition flow. The k-$$omega$$-SST model was selected for turbulent calculation attributed to predict the effects mentioned above adequately. The numerical results using the k-$$omega$$-SST model reproduced the temperature distribution of PV especially the top region which is considered to be affected by separation, re-adhesion and transition flow in contract to that using k-$$varepsilon$$ model which does not account the effects.

JAEA Reports

Preliminary combustion analyses using OpenFOAM

Thwe Thwe, 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

Current R&D status of thermochemical water splitting hydrogen production iodine-sulfur process in Japan Atomic Energy Agency, 1; Hydrogen production test and component development

Takegami, Hiroaki; Noguchi, Hiroki; Tanaka, Nobuyuki; Iwatsuki, Jin; Kamiji, Yu; Kasahara, Seiji; Imai, Yoshiyuki; Terada, Atsuhiko; Kubo, Shinji

Proceedings of 9th International Topical Meeting on High Temperature Reactor Technology (HTR 2018) (USB Flash Drive), 7 Pages, 2018/10

Japan Atomic Energy Agency (JAEA) has been conducting R&D on the thermochemical iodine-sulfur (IS) process for nuclear-powered hydrogen production. The IS process is one of the promising candidates of heat application of the high-temperature gas-cooled reactors. JAEA fabricated main chemical reactors made of industrial structural materials and confirmed their integrity in practical corrosive environments in the IS process. Based on the results of these confirmation tests, JAEA have constructed a 100 NL/h-H$$_{2}$$-scale test facility made of industrial structural materials. This report will present an outline and results of hydrogen production tests and reliability improvements of operation stability and components, such as development of a strength estimation method for heat-resistant and corrosion-resistant ceramics components made of silicon carbide.

Journal Articles

A Concept of intermediate heat exchanger for high-temperature gas reactor hydrogen and power cogeneration system

Hirota, Noriaki; Terada, Atsuhiko; Yan, X.; Tanaka, Kohei*; Otani, Akihito*

Proceedings of 26th International Conference on Nuclear Engineering (ICONE-26) (Internet), 7 Pages, 2018/07

Journal Articles

Design of HTTR-GT/H$$_{2}$$ test plant

Yan, X.; Sato, Hiroyuki; Sumita, Junya; Nomoto, Yasunobu*; Horii, Shoichi*; Imai, Yoshiyuki; Kasahara, Seiji; Suzuki, Koichi*; Iwatsuki, Jin; Terada, Atsuhiko; et al.

Nuclear Engineering and Design, 329, p.223 - 233, 2018/04

 Times Cited Count:27 Percentile:92.35(Nuclear Science & Technology)

The pre-licensing design of an HTGR cogeneration test plant to be coupled to JAEA's existing test reactor HTTR is presented. The plant is designed to demonstrate the system of JAEA commercial plant design GTHTR300C. With construction planned to be completed around 2025, the test plant is expected to be the first-of-a-kind nuclear system operating on two of the advanced energy conversion systems attractive for the HTGR closed cycle helium gas turbine for power generation and thermochemical iodine-sulfur water-splitting process for hydrogen production.

Journal Articles

Conceptual design of the iodine-sulfur process flowsheet with more than 50% thermal efficiency for hydrogen production

Kasahara, Seiji; Imai, Yoshiyuki; Suzuki, Koichi*; Iwatsuki, Jin; Terada, Atsuhiko; Yan, X.

Nuclear Engineering and Design, 329, p.213 - 222, 2018/04

 Times Cited Count:26 Percentile:91.11(Nuclear Science & Technology)

A conceptual design of a practical large scale plant of the thermochemical water splitting iodine-sulfur (IS) process flowsheet was carried out as a heat application of JAEA's commercial high temperature gas cooled reactor GTHTR300C plant design. Innovative techniques proposed by JAEA were applied for improvement of hydrogen production thermal efficiency; depressurized flash concentration H$$_{2}$$SO$$_{4}$$ using waste heat from Bunsen reaction, prevention of H$$_{2}$$SO$$_{4}$$ vaporization from a distillation column by introduction of H$$_{2}$$SO$$_{4}$$ solution from a flash bottom, and I$$_{2}$$ condensation heat recovery in an HI distillation column. Hydrogen of about 31,900 Nm$$^{3}$$/h would be produced by 170 MW heat from the GTHTR300C. A thermal efficiency of 50.2% would be achievable with incorporation of the innovative techniques and high performance HI concentration and decomposition components and heat exchangers expected in future R&D.

Journal Articles

HTTR-GT/H$$_{2}$$ test plant; System design

Yan, X.; Sato, Hiroyuki; Sumita, Junya; Nomoto, Yasunobu; Horii, Shoichi; Imai, Yoshiyuki; Kasahara, Seiji; Suzuki, Koichi*; Iwatsuki, Jin; Terada, Atsuhiko; et al.

Proceedings of 8th International Topical Meeting on High Temperature Reactor Technology (HTR 2016) (CD-ROM), p.827 - 836, 2016/11

Pre-licensing basic design for a cogenerating HTGR test plant system is presented. The plant to be coupled to existing 30 MWt 950$$^{circ}$$C test reactor HTTR is intended as a system technology demonstrator for GTHTR300C plant design. More specifically the test plant of HTTR-GT/H$$_{2}$$ aims to (1)demonstrate the licensability of the GTHTR300C for electricity production by gas turbine and hydrogen cogeneration by thermochemical process and (2) confirm the operation control and safety of such cogeneration system. With construction and operation completion by 2025, the test plant is expected to be the first of a kind HTGR-powered cogeneration plant operating on the two advanced energy conversion systems of closed cycle helium gas turbine for power generation and thermochemical iodine-sulfur water-splitting process for hydrogen production.

Journal Articles

Conceptual design of iodine-sulfur process flowsheet with more than 50% thermal efficiency for hydrogen production

Kasahara, Seiji; Imai, Yoshiyuki; Suzuki, Koichi*; Iwatsuki, Jin; Terada, Atsuhiko; Yan, X.

Proceedings of 8th International Topical Meeting on High Temperature Reactor Technology (HTR 2016) (CD-ROM), p.491 - 500, 2016/11

A conceptual design of a practical large scale plant of the thermochemical water splitting iodine-sulfur (IS) process flowsheet was carried out as a heat application of Japan Atomic Energy Agency's commercial Gas Turbine High Temperature Reactor Cogeneration (GTHTR300C) plant design. Innovative techniques proposed by JAEA were applied for improvement of hydrogen production thermal efficiency; flash concentration of H$$_{2}$$SO$$_{4}$$ using waste heat from Bunsen reaction, prevention of H$$_{2}$$SO$$_{4}$$ vaporization from a distillation column by introduction of H$$_{2}$$SO$$_{4}$$ solution, and I$$_{2}$$ condensation heat recovery by direct contact heat exchange in the HI distillation column. A simulation of material and heat balance showed hydrogen of about 31,900 Nm$$^{3}$$/h was produced by 170 MW heat from the GTHTR300C. A process thermal efficiency of 50.2% was achievable with incorporation of the innovative techniques and several high performance components expected in future R&D.

Journal Articles

GTHTR300 cost reduction through design upgrade and cogeneration

Yan, X.; Sato, Hiroyuki; Kamiji, Yu; Imai, Yoshiyuki; Terada, Atsuhiko; Tachibana, Yukio; Kunitomi, Kazuhiko

Nuclear Engineering and Design, 306, p.215 - 220, 2016/09

 Times Cited Count:6 Percentile:40.14(Nuclear Science & Technology)

The latest design upgrade has incorporated several major technological advances made in the past ten years to both reactor and balance of plant in GTHTR300. As described in this paper, these advances have enabled raising the design basis reactor core outlet temperature to 950$$^{circ}$$C and increasing power generating efficiency by nearly 5% point. Further implementation of seawater desalination cogeneration is made through employing a newly-proposed multi-stage flash process. Through efficient waste heat recovery of the reactor gas turbine power conversion cycle, a large cost credit is obtained against the conventionally produced water prices. Together, the design upgrade and the cogeneration are shown to reduce the GTHTR300 cost of electricity to under 2.7 cent/kW h.

Journal Articles

HTTR demonstration program for nuclear cogeneration of hydrogen and electricity

Sato, Hiroyuki; Yan, X.; Sumita, Junya; Terada, Atsuhiko; Tachibana, Yukio

Journal of Nuclear Engineering and Radiation Science, 2(3), p.031010_1 - 031010_6, 2016/07

This paper explains the outline of HTTR demonstration program with a plant concept of the heat application system directed at establishing an HTGR cogeneration system with 950$$^{circ}$$C reactor outlet temperature for production of power and hydrogen as recommended by the task force. Commercial deployment strategy including a development plan for the helium gas turbine is also presented.

Journal Articles

Heat transport analysis in a district heating system applying waste heat from GTHTR300, a commercial design of high-temperature gas-cooled reactor

Kasahara, Seiji; Murata, Tetsuya*; Kamiji, Yu; Terada, Atsuhiko; Yan, X.; Inagaki, Yoshiyuki; Mori, Michitsugu*

Mechanical Engineering Journal (Internet), 3(3), p.15-00616_1 - 15-00616_16, 2016/06

A district heating system for household heating and road snow melting utilizing waste heat from GTHTR300, a heat-electricity cogeneration design of high temperature gas-cooled reactor, was analyzed. The application area was Sapporo and Ishikari, cities with heavy snowfall in northern Japan. The heat transport analyses were performed by modeling components to estimate heat supply profile; the secondary loops between the GTHTR300s and the heat-application area; heat exchangers connecting the secondary loops to the tertiary loops of the district-heating pipes; and the tertiary loops between the heat exchangers and houses and roads. Though double pipes for the secondary loops were advantageous for having less heat loss and a smaller excavation area, these advantages did not compensate for the higher construct cost of the pipes. To satisfy heat demand in the month of maximum requirement, 520-529 MW of heat were supplied by 3 GTHTR300s and delivered by 6 secondary loops, 3,450 heat exchangers about 90 m long, and 3,450 tertiary loops. Heat loss to the ground from the tertiary loops comprised 80%-90% of the heat loss. More than 90% of the construction cost went into thermal insulators. The thickness and properties of the thermal insulator must be reevaluated for economical heat delivery.

Journal Articles

Automated control for electric-thermal load following operation in nuclear gas turbine cogeneration system

Sato, Hiroyuki; Yan, X.; Sumita, Junya; Terada, Atsuhiko; Nishihara, Tetsuo

Proceedings of International Gas Turbine Congress 2015 (IGTC 2015) (DVD-ROM), p.184 - 190, 2015/11

This paper presents the original control system design to provide for an extended range of electrical-thermal load-following in the GTHTR300. The turbine speed control is newly added to the basic plant control to take full advantage of the system characteristics of the HTGR and the closed-cycle gas turbine to accomplish the design goal of maintaining constant reactor power and high thermal efficiency during the load-following operation. Simulation result presented in the paper shows that the design goal can be effectively met. The paper also describes a demonstration program to validate the system operability by connecting an electricity and hydrogen cogeneration plant to the HTTR.

202 (Records 1-20 displayed on this page)