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Journal Articles

VHTR technology development in Japan; Progress of R&D activities for GIF VHTR system

Shibata, Taiju; Sato, Hiroyuki; Ueta, Shohei; Takegami, Hiroaki; Takada, Shoji; Kunitomi, Kazuhiko

2018 GIF Symposium Proceedings (Internet), p.99 - 106, 2020/05

no abstracts in English

JAEA Reports

Excellent feature of Japanese HTGR technologies

Nishihara, Tetsuo; Yan, X.; Tachibana, Yukio; Shibata, Taiju; Ohashi, Hirofumi; Kubo, Shinji; Inaba, Yoshitomo; Nakagawa, Shigeaki; Goto, Minoru; Ueta, Shohei; et al.

JAEA-Technology 2018-004, 182 Pages, 2018/07

JAEA-Technology-2018-004.pdf:18.14MB

Research and development on High Temperature Gas-cooled Reactor (HTGR) in Japan started since late 1960s. Japan Atomic Energy Agency (JAEA) in cooperation with Japanese industries has researched and developed system design, fuel, graphite, metallic material, reactor engineering, high temperature components, high temperature irradiation and post irradiation test of fuel and graphite, high temperature heat application and so on. Construction of the first Japanese HTGR, High Temperature engineering Test Reactor (HTTR), started in 1990. HTTR achieved first criticality in 1998. After that, various test operations have been carried out to establish the Japanese HTGR technologies and to verify the inherent safety features of HTGR. This report presents several system design of HTGR, the world-highest-level Japanese HTGR technologies, JAEA's knowledge obtained from construction, operation and management of HTTR and heat application technologies for HTGR.

Journal Articles

The Development status of Generation IV reactor systems, 2; High temperature gas-cooled reactor (HTGR)

Kunitomi, Kazuhiko; Nishihara, Tetsuo; Yan, X.; Tachibana, Yukio; Shibata, Taiju

Nippon Genshiryoku Gakkai-Shi, 60(4), p.236 - 240, 2018/04

High temperature gas-cooled reactor (HTGR) is a graphite-moderated and helium-gas-cooled thermal-neutron reactor that has excellent safety features and can produce high temperature heat of 950$$^{circ}$$C. It is expected to use for various heat applications as well as for electricity generation to reduce carbon dioxide emission. Japan Atomic Energy Agency (JAEA) has been promoted research and development to demonstrate the HTGR safety features using High temperature engineering test reactor (HTTR) and it's heat application. JAEA are also conducting the action to international deployment of Japanese HTGR technologies in cooperation with industries-government-academia. This paper reports status of the research and development of HTGR and domestic and international collaborations.

Journal Articles

Development of safety requirements for HTGRs design

Ohashi, Hirofumi; Sato, Hiroyuki; Nakagawa, Shigeaki; Tokuhara, Kazumi; Nishihara, Tetsuo; Kunitomi, Kazuhiko

Proceedings of 8th International Topical Meeting on High Temperature Reactor Technology (HTR 2016) (CD-ROM), p.330 - 340, 2016/11

The safety requirements for the design of HTGRs has been developed by the research committee established in the Atomic Energy Society of Japan so as to incorporate the HTGR safety features demonstrated by HTTR, lessons learned from the accident of Fukushima Daiichi Nuclear Power Station and requirements for the coupling of the hydrogen production plants with nuclear plant. The safety design approach was determined to establish a high level of safety design standards by utilizing inherent safety features of HTGRs. This paper describes the process to develop the HTGR specific safety requirements and overview of the proposed HTGR specific safety requirements.

Journal Articles

The IAEA coordinated research project on modular HTGR safety design; Status and outlook

Reitsma, F.*; Kunitomi, Kazuhiko; Ohashi, Hirofumi

Proceedings of 8th International Topical Meeting on High Temperature Reactor Technology (HTR 2016) (CD-ROM), p.341 - 352, 2016/11

The IAEA Coordinated Research Project (CRP) on Modular High Temperature Gas-cooled Reactor (HTGR) Safety Design started in December 2014 and is now in its second year of implementation. The project investigates and makes proposals on safety design criteria by not only considering the existing water cooled reactors safety requirements for nuclear power plant design but also making use of past and current experience of HTGR licensing in the IAEA member states including Japan. The detailed project content and a description of modular HTGRs and its safety features are given. This informs the comments made on the applicability of the existing requirements and the examples of newly proposed HTGR specific safety requirements under development.

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:2 Percentile:69.03(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

Study on reduction of potential radiotoxicity for spent fuel by using HTGR

Fukaya, Yuji; Kunitomi, Kazuhiko; Ogawa, Masuro

Nippon Genshiryoku Gakkai Wabun Rombunshi, 14(3), p.189 - 201, 2015/09

A study on reduction of potential radiotoxicity for spent fuel by using High Temperature Gas-cooled Reactors (HTGRs) have been performed. Unlike Partitioning and Transmutation (P&T), the reactor concept is investigated from the viewpoint of reduction of the radiotoxicity generation itself. To reduce the radiotoxicity, $$^{238}$$U, which generates Pu, Am and Cm, should be excluded. Therefore, we proposed HTGR fueled by new concept fuels with alternative fuel matrix instead of $$^{238}$$U. Those are Yttria Stabilized Zirconia (YSZ) and thorium, and the fissile material is Highly Enriched Uranium (HEU) with the enrichment of 93%. With the HEU, the radiotoxicity can be significantly reduced, and the cooling time to decay to a natural uranium level can be shorted down to approximately 800 years. Fuel integrity and proliferation resistance can be remained by the dilution using YSZ, and neutronic characteristics of self-regulation is remained by the loading of erbium. The fuel can generate heat as same amount as ordinary uranium fuel. The electricity generation cost is as cheap as ordinary GTHTR300. It is concluded that the proposed reactor concept can reduce the cooling time less than 1% from 100 thousand years to a 800 years without additional technology development.

Journal Articles

Conceptual study of a plutonium burner high temperature gas-cooled reactor with high nuclear proliferation resistance

Goto, Minoru; Demachi, Kazuyuki*; Ueta, Shohei; Nakano, Masaaki*; Honda, Masaki*; Tachibana, Yukio; Inaba, Yoshitomo; Aihara, Jun; Fukaya, Yuji; Tsuji, Nobumasa*; et al.

Proceedings of 21st International Conference & Exhibition; Nuclear Fuel Cycle for a Low-Carbon Future (GLOBAL 2015) (USB Flash Drive), p.507 - 513, 2015/09

A concept of a plutonium burner HTGR named as Clean Burn, which has a high nuclear proliferation resistance, had been proposed by Japan Atomic Energy Agency. In addition to the high nuclear proliferation resistance, in order to enhance the safety, we propose to introduce PuO$$_{2}$$-YSZ TRISO fuel with ZrC coating to the Clean Burn. In this study, we conduct fabrication tests aiming to establish the basic technologies for fabrication of PuO$$_{2}$$-YSZ TRISO fuel with ZrC coating. Additionally, we conduct a quantitative evaluation of the security for the safety, a design of the fuel and the reactor core, and a safety evaluation for the Clean Burn to confirm the feasibility. This study is conducted by The University of Tokyo, Japan Atomic Energy Agency, Fuji Electric Co., Ltd., and Nuclear Fuel Industries, Ltd. It was started in FY2014 and will be completed in FY2017, and the first year of the implementation was on schedule.

Journal Articles

Safety design consideration for HTGR coupling with hydrogen production plant

Sato, Hiroyuki; Ohashi, Hirofumi; Nakagawa, Shigeaki; Tachibana, Yukio; Kunitomi, Kazuhiko

Progress in Nuclear Energy, 82, p.46 - 52, 2015/07

 Times Cited Count:7 Percentile:32.99(Nuclear Science & Technology)

Safety requirements and design considerations for a HTGR hydrogen production system by IS process are examined. Requirements in order to construct hydrogen production plants under conventional chemical plant regulation are identified. In addition, safety requirements for the collocation of the nuclear facility and hydrogen production plant utilizing IS process are investigated. Furthermore, design considerations to comply with the requirements are suggested and the technical feasibility of the design considerations is evaluated. The evaluation results clarified that design considerations suggested for coupling IS plant to HTGR are reasonably practicable.

Journal Articles

Energy neutral phosphate fertilizer production using high temperature reactors; A Philippine case study

Haneklaus, N.*; Reyes, R.*; Lim, W. G.*; Tabora, E. U.*; Palattao, B. L.*; Petrache, C.*; Vargas, E. P.*; Kunitomi, Kazuhiko; Ohashi, Hirofumi; Sakaba, Nariaki; et al.

Philippine Journal of Science, 144(1), p.69 - 79, 2015/06

The Philippines may profit from extracting uranium (U) from phosphoric acid during fertilizer production in a way that the recovered U can be beneficiated and taken as raw material for nuclear reactor fuel. Used in a high temperature reactor (HTR) that provides electricity and/or process heat for fertilizer processing and U extraction, energy-neutral fertilizer production, an idea first proposed by Haneklaus et al., is possible. This paper presents a first case study of the concept regarding a representative phosphate fertilizer plant in the Philippines and exemplary HTR designs (HTR50S and GTHTR300C) developed by the Japan Atomic Energy Agency (JAEA). Three different arrangements (version I-III), ranging from basic electricity supply to overall power supply including on site hydrogen production for ammonia conversion, are introduced and discussed.

Journal Articles

Thermal analysis of heated cylinder simulating nuclear reactor during loss of coolant accident

Sato, Hiroyuki; Ohashi, Hirofumi; Tachibana, Yukio; Kunitomi, Kazuhiko; Ogawa, Masuro

Journal of Nuclear Science and Technology, 51(11-12), p.1317 - 1323, 2014/11

 Times Cited Count:7 Percentile:39.01(Nuclear Science & Technology)

Transient analyses are presented of temperature behavior of reactor during loss-of-coolant accident with scram. The influence of reactor thermal properties, operating power density, geometry of active core and selection of fuel type on the capability of decay heat removal against the accident are studied. It is shown that the reactor design envelope is fully determined by the key parameters. The range of the envelope is shown to enlarge considerably by selecting high refractory fuel. High temperature gas-cooled reactor (HTGR), a graphite-moderated reactor with TRISO coated fuel particle, is the primary candidate which can fulfill the requirement to the design concept of nuclear reactor independent of coolant for decay heat removal.

Journal Articles

Validation and application of thermal hydraulic system code for analysis of helically coiled heat exchanger in high-temperature environment

Sato, Hiroyuki; Ohashi, Hirofumi; Nakagawa, Shigeaki; Tachibana, Yukio; Kunitomi, Kazuhiko

Journal of Nuclear Science and Technology, 51(11-12), p.1324 - 1335, 2014/11

 Times Cited Count:4 Percentile:59.06(Nuclear Science & Technology)

A qualification of the thermal hydraulic system code RELAP5 code is conducted for the analysis of helically-coiled heat exchangers used in high temperature environment. The experimental data obtained from the HTTR are utilized to compare with calculated data by RELAP5-based model with built-in closure models. A set of closure model is also suggested considering the heat transfer enhancement by thermal radiation based on the past separate effect test data and validated against the measured data. In addition, the modified RELAP5 code is tested for the analysis of the HTTR-IS system. The comparison of calculated and measure data with steady state operation showed that the prediction temperature with the suggested model generally agreed well. As a conclusion of the present study, the use of thermal hydraulic system code with the suggested closure model is acceptable for the analysis of the IHX in HTGR nuclear hydrogen production systems in the safety evaluation.

Journal Articles

Experiments and validation analyses of HTTR on loss of forced cooling under 30% reactor power

Takamatsu, Kuniyoshi; Tochio, Daisuke; Nakagawa, Shigeaki; Takada, Shoji; Yan, X.; Sawa, Kazuhiro; Sakaba, Nariaki; Kunitomi, Kazuhiko

Journal of Nuclear Science and Technology, 51(11-12), p.1427 - 1443, 2014/11

 Times Cited Count:9 Percentile:29.95(Nuclear Science & Technology)

In a safety demonstration test involving a loss of both reactor reactivity control and core cooling, HTGRs such as the HTTR, which is the only HTGR in Japan, demonstrate that the reactor power would stabilize spontaneously. In the test at an initial power of 30%, when the insertion of all control rods was disabled and all gas circulators were tripped to reduce the coolant flow rate to zero, a reactor transient was initiated and examined. The results confirmed that the reactor power would decrease immediately and become effectively zero.

Journal Articles

Safety design approach for the development of safety requirements for design of commercial HTGR

Ohashi, Hirofumi; Sato, Hiroyuki; Nakagawa, Shigeaki; Tachibana, Yukio; Nishihara, Tetsuo; Yan, X.; Sakaba, Nariaki; Kunitomi, Kazuhiko

Proceedings of 7th International Topical Meeting on High Temperature Reactor Technology (HTR 2014) (USB Flash Drive), 10 Pages, 2014/10

The research committee on Safety requirements for HTGR design was established in 2013 under the Atomic Energy Society of Japan to develop the draft safety requirements for the design of commercial High Temperature Gas-cooled Reactor (HTGR), which incorporate the HTGR safety features demonstrated using the High Temperature Engineering Test Reactor (HTTR), lessons learned from the accident of Fukushima Daiichi Nuclear Power Station and requirements for the integration of the hydrogen production plants. The safety design approach for the commercial HTGR which is a basement of the safety requirements is determined prior to the development of the safety requirements. This paper describes the main topics of the research committee, the safety design approaches and the safety functions of the commercial HTGR determined in the research committee.

Journal Articles

GTHTR300 cost reduction through design upgrade and cogeneration

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

Proceedings of 7th International Topical Meeting on High Temperature Reactor Technology (HTR 2014) (USB Flash Drive), 7 Pages, 2014/10

The latest design upgrade has incorporated several major technological advances made in the past 10 years to GTHTR300. These advances have enabled raising the design basis reactor outlet temperature to 950$$^{circ}$$C and increasing power generating efficiency by nearly 5% point. Further implementation of desalination cogeneration is made through employing a newly-proposed multi-stage flash process. Through efficient waste heat recovery of the reactor gas turbine cycle, a large cost credit is obtained against the conventionally produced water prices. Together, the design upgrade and the cogeneration result in reducing the GTHTR300 cost of electricity to under 2.7 US cent per KWh.

JAEA Reports

Economic evaluation of HTGR IS process hydrogen production system

Iwatsuki, Jin; Kasahara, Seiji; Kubo, Shinji; Inagaki, Yoshiyuki; Kunitomi, Kazuhiko; Ogawa, Masuro

JAEA-Review 2014-037, 14 Pages, 2014/09

JAEA-Review-2014-037.pdf:8.84MB

Thermochemical iodine-sulfur (IS) process is one of the promising technologies, which harnesses heat energy of high temperature gas-cooled reactors (HTGRs). An economic estimation of hydrogen production by a future commercial HTGR-IS process hydrogen production system was performed on the basis of economic evaluation data of an existing commercial hydrogen production plant using fossil fuel as a raw material. Hydrogen production cost was estimated at 25.4 JPY/Nm$$^{3}$$ under this estimation conditions. Capital cost and energy cost account for 13% and 78% of the total hydrogen production cost, respectively. To decrease HTGR construction cost, to increase HTGR availability, to improve hydrogen production thermal efficiency are important for cost reduction of hydrogen. The cost will be competitive with estimated costs by fossil fuel hydrogen production methods. It is appropriate that the hydrogen production cost is set for a goal of present R&Ds.

Journal Articles

GTHTR300; A Nuclear power plant design with 50% generating efficiency

Sato, Hiroyuki; Yan, X.; Tachibana, Yukio; Kunitomi, Kazuhiko

Nuclear Engineering and Design, 275, p.190 - 196, 2014/08

 Times Cited Count:16 Percentile:13.25(Nuclear Science & Technology)

Three major improvements have since been made to further increase efficiency for the GTHTR300. First, the cycle parameters are upgraded by utilizing the newly-acquired design data including those from component tests. Next, the core design is optimized to raise the reactor outlet coolant temperature from the baseline of 850$$^{circ}$$C to the level of 950$$^{circ}$$C demonstrated on the long-term test reactor operation. Finally, an advanced type of turbine blade material that has only recently entered in commercial service in aircraft engine is found to be useable for this design to realize a turbine inlet temperature of 950$$^{circ}$$C without requiring blade cooling. These design improvements result in a nearly 5% gain in overall plant efficiency and enable the GTHTR300 to break the 50% efficiency barrier of nuclear plant while using only the existing technologies.

Journal Articles

Basic philosophy on super safe reactor

Okamoto, Koji*; Kunitomi, Kazuhiko

Enerugi Rebyu, 34(6), p.7 - 10, 2014/06

This document clearly describes the safety of HTGR in comparison with LWR and its development status. In HTGR, the safety functions to stop and cool the reactor, and contain fission products in the reactor are ensured by natural phenomena, not depending on additional safety systems. Therefore, the HTGR is inherently safe and can be easily operated and controlled. In Japan, Japan Atomic Energy Agency and nuclear industries have long been developing the HTGR and constructed the High Temperature Engineering Test Reactor (HTTR) in Oarai Research Center to establish world leading HTGR technology. The HTGR should be developed as a safe nuclear reactor in Japan and can be exported worldwide as a Japanese strategic technology.

Journal Articles

Proposal of a plutonium burner system based on HTGR with high proliferation resistance

Fukaya, Yuji; Goto, Minoru; Ohashi, Hirofumi; Tachibana, Yukio; Kunitomi, Kazuhiko; Chiba, Satoshi*

Journal of Nuclear Science and Technology, 51(6), p.818 - 831, 2014/06

AA2012-0626.pdf:0.9MB

 Times Cited Count:15 Percentile:14.54(Nuclear Science & Technology)

A plutonium burner HTGR concept of "Clean Burn" has been investigated based on the experience with the HTTR construction and operation, and the GTHTR300 design. The concept aims at effective and safe consumption of the surplus plutonium from LWR spent fuel once through. The Clean Burn employs IMF that can be fabricated without a need to mix the plutonium with uranium. In addition, the incineration of the plutonium can be performed effectively without plutonium generation from the matrix and the reactivity defect. The IMF is also made into a highly stable form to keep fuel integrity and geological disposal stability. The particular fabrication system and the stable form make the IMF more proliferation resistant than the conventional LWR-MOX fuel. This advantage is attractive to the Japanese nuclear fuel cycle policy. Moreover, the Clean Burn has naturally safe feature because based on HTGR concept. A detailed investigation have shown that the proposed concept is effective and promising.

Journal Articles

Spontaneous stabilization of HTGRs without reactor scram and core cooling; Safety demonstration tests using the HTTR: Loss of reactivity control and core cooling

Takamatsu, Kuniyoshi; Yan, X.; Nakagawa, Shigeaki; Sakaba, Nariaki; Kunitomi, Kazuhiko

Nuclear Engineering and Design, 271, p.379 - 387, 2014/05

 Times Cited Count:5 Percentile:51.32(Nuclear Science & Technology)

In this study, an all-gas-circulator trip test was analyzed as a loss of forced cooling (LOFC) test with an initial reactor power of 9 MW to demonstrate LOFC accidents. The analytical results indicate that reactor power decreases from 9 MW to 0 MW owing to the negative reactivity feedback effect of the core, even if the reactor shutdown system is not activated. The total reactivity decreases and then gradually increases in proportion to xenon reactivity; therefore, the HTTR achieves recritical after an elapsed time, which is different from the elapsed time at reactor power peak occurrence. After the reactor power peak occurs, the total reactivity oscillates several times because of the negative reactivity feedback effect and gradually decreases to zero. Moreover, the new conclusions are as follows: The minimum reactor power and the reactor power peak occurrence are affected by the neutron source. The greater the strength of the neutron source, the larger the minimum reactor power.

223 (Records 1-20 displayed on this page)