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Journal Articles

Development of cesium trap material for coated fuel particles in high temperature gas-cooled reactors

Sasaki, Koei; Miura, Shuichiro*; Fukumoto, Kenichi*; Goto, Minoru; Ohashi, Hirofumi

Proceedings of 28th International Conference on Nuclear Engineering; Nuclear Energy the Future Zero Carbon Power (ICONE 28) (Internet), 6 Pages, 2021/08

Cs-Bi and Cs-Sb absorbed graphite samples (Cs-Bi/graphite and Cs-Sb/graphite) were synthesized and their high temperature chemical stabilities were tested up to 1500$$^{circ}$$C by TG and analyzed by TEM-EDS for the development of Cs trap material in high temperature gas-cooled reactor (HTGR) fuel particles. It was observed that Cs was stabilized by Sb but not by Bi in the specimens after the TG test. A rapid weight loss from 800 to 1000$$^{circ}$$C may be caused by evaporation of Cs (boiling point: 671$$^{circ}$$C) was seen in the TG result of both specimens. Precipitated Cs-Sb substance in the graphite matrix were not resolved even after the 1500$$^{circ}$$C heating. The chemical composition of the Cs-Sb was specified as Cs$$_{3}$$Sb. The experimental results suggest that Sb have potential to be a Cs getter material in graphite matrix. Long term heating test should be performed to confirm adaptability of Sb for Cs trap material in HTGR fuel particles.

Journal Articles

Feasibility study on burnable poison credit concept to HTGR fuel fabrication from core specification perspective

Fukaya, Yuji; Ueta, Shohei; Goto, Minoru; Ohashi, Hirofumi

Annals of Nuclear Energy, 151, p.107937_1 - 107937_9, 2021/02

 Times Cited Count:1 Percentile:0.01(Nuclear Science & Technology)

Feasibility study on Burnable Poison (BP) credit concept to High Temperature Gas-cooled Reactor (HTGR) fuel fabrication has been performed. By mixing BP into fuel material in the first place of fuel fabrication, criticality safety is ensured in the all fuel fabrication process even with high enrichment fuel such as 14 wt% used in commercial HTGR. However, the poison effect also prevents the criticality even in the HTGR core, and it may shorten cycle length and achievable burn-up of the core. Therefore, the effect is evaluated by whole core burn-up calculation. As a BP, boron, gadolinium, erbium, and hafnium are investigated. As a result, it is found that boron and gadolinium suit this concept and the 14 wt% fuel can be fabricated in the plant fabricating 9.9 wt% High Temperature engineering Test Reactor (HTTR) fuel. With the boron and gadolinium, the commercial HTGR fuel can be fabricated with the safety measure as same as Light Water Reactor (LWR) fuel facility to treat the fuel with the enrichment up to 5 wt%. Especially, gadolinium is significantly suitable to this concept due to the dependency to spectrum, and more enhanced safety measure is feasible as well.

Journal Articles

High temperature gas-cooled reactors

Takeda, Tetsuaki*; Inagaki, Yoshiyuki; Aihara, Jun; Aoki, Takeshi; Fujiwara, Yusuke; Fukaya, Yuji; Goto, Minoru; Ho, H. Q.; Iigaki, Kazuhiko; Imai, Yoshiyuki; et al.

High Temperature Gas-Cooled Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.5, 464 Pages, 2021/02

As a general overview of the research and development of a High Temperature Gas-cooled Reactor (HTGR) in JAEA, this book describes the achievements by the High Temperature Engineering Test Reactor (HTTR) on the designs, key component technologies such as fuel, reactor internals, high temperature components, etc., and operational experience such as rise-to-power tests, high temperature operation at 950$$^{circ}$$C, safety demonstration tests, etc. In addition, based on the knowledge of the HTTR, the development of designs and component technologies such as high performance fuel, helium gas turbine and hydrogen production by IS process for commercial HTGRs are described. These results are very useful for the future development of HTGRs. This book is published as one of a series of technical books on fossil fuel and nuclear energy systems by the Power Energy Systems Division of the Japan Society of Mechanical Engineers.

Journal Articles

Research and development activities of JAEA for HTGR system realization

Mineo, Hideaki; Nishihara, Tetsuo; Ohashi, Hirofumi; Goto, Minoru; Sato, Hiroyuki; Takegami, Hiroaki

Nihon Genshiryoku Gakkai-Shi ATOMO$$Sigma$$, 62(9), p.504 - 508, 2020/09

High-Temperature Gas-cooled Reactor (HTGR) is one of thermal neutron reactor-type that employs helium gas coolant and graphite moderator. It has excellent inherent safety and can supply high-temperature heat which can be used not only for electric power generation but also for a wide range of application such as hydrogen production. Therefore, HTGR is expected to be an effective technology for reducing greenhouse gases in Japan as well as overseas. In this paper, we will introduce the forefront of technological development that JAEA is working toward the realization of an HTGR system consisting of a high temperature gas reactor and heat utilization facilities such as gas-turbine power generation and hydrogen production.

Journal Articles

Guidance for developing fuel design limit of high temperature gas-cooled reactor

Sato, Hiroyuki; Aoki, Takeshi; Ohashi, Hirofumi

Proceedings of 2020 International Conference on Nuclear Engineering (ICONE 2020) (Internet), 10 Pages, 2020/08

The present study aims to propose a guidance that facilitates to determine fuel design limits of commercial HTGR on the basis of licensing experience through the HTTR construction. The guidance consists of a set of FOMs and a process to determine their evaluation criteria. The FOMs are firstly identified to satisfy safety requirements and a basic concept of safety guides established in a special committee under the AESJ with the support of the Research Association of High Temperature Gas Cooled Reactor Plant. The development process for the evaluation criteria takes into account not only the top-level regulatory criteria but also design dependent constraints including the performance of fission product containment in physical barriers other than fuel, fuel qualification criteria, design specifications of an instrumentation and control system. As a result, a comprehensive and transparent procedure for designers of prismatic-type commercial HTGR has been developed.

Journal Articles

Methodology development for transient flow distribution analysis in high temperature gas-cooled reactor

Aoki, Takeshi; Sato, Hiroyuki; Ohashi, Hirofumi

Proceedings of 2020 International Conference on Nuclear Engineering (ICONE 2020) (Internet), 6 Pages, 2020/08

The flow distribution analysis, which is a part of thermal hydraulic design of the prismatic-type of the high temperature gas cooled reactor (HTGR) considering unintended flows between graphite blocks, has been performed for steady and conservative conditions. On the other hand, the transient analysis for satisfactorily realistic conditions will be helpful for the design improvement of prismatic-type HTGR. The present study aims to develop the transient flow distribution analysis code and confirm its applicability for the transient flow distribution analysis for prismatic-type HTGRs during anticipated operational occurrences and accidents utilizing experiences on high temperature engineering test reactor (HTTR) design. The calculation model and code were developed and validated for analysis of the unintended flows in the core and the molecular diffusion dominant in beginning air ingress behavior in an air ingress accident.

Journal Articles

Development of a flow network calculation code (FNCC) for high temperature gas-cooled reactors (HTGRs)

Aoki, Takeshi; Isaka, Kazuyoshi; Sato, Hiroyuki; Ohashi, Hirofumi

Proceedings of 2020 International Conference on Nuclear Engineering (ICONE 2020) (Internet), 7 Pages, 2020/08

The flow distribution analysis performed in the HTGR design has to take into account the interaction thermal and radiation deformations of the graphite structure, and the gaps between the graphite structures forming unintended flow. In the present study, a user-friendly flow network calculation code (FNCC) has been developed on the basis of experiences of High Temperature engineering Test Reactor (HTTR) design for HTGR design with enhanced compatibility with other HTGR design codes and with considering graphite block deformation in iteration process without manual control. The validation of FNCC was performed for the one-column flow distribution test. The analytical results using FNCC showed good agreement with the experimental results. It is concluded that FNCC was validate for the analysis of distributions of flowrate and pressure for the flow network model including the unintended flow paths in prismatic-type HTGRs.

Journal Articles

Uncertainty analysis of toxic gas leakage accident in cogeneration high temperature gas-cooled reactor

Sato, Hiroyuki; Ohashi, Hirofumi

Mechanical Engineering Journal (Internet), 7(3), p.19-00332_1 - 19-00332_11, 2020/06

An uncertainty analysis method for control room habitability under toxic gas leakage accidents in cogeneration HTGR is proposed to support risk-informed design of the plant. The method is applied to representative toxic gas leakage accidents in a IS process hydrogen production plant coupled to the HTTR gas turbine test plant. Epistemic and aleatory uncertainties for each variable parameter are identified and are propagated using Latin hypercube sampling. The analyses show that the suggested method can successfully characterize and quantify uncertainties in the toxic gas concentration in control room. The results lead us to the conclusion that toxic gas dispersion behavior analysis should combine two evaluation methods: dense gas dispersion model and computational fluid dynamics simulation.

Journal Articles

Research and development on high burnup HTGR fuels in JAEA

Ueta, Shohei; Mizuta, Naoki; Sasaki, Koei; Sakaba, Nariaki; Ohashi, Hirofumi; Yan, X.

Mechanical Engineering Journal (Internet), 7(3), p.19-00571_1 - 19-00571_12, 2020/06

JAEA has been progressing to design HTGR fuels for not only small-type practical HTGRs but also VHTR proposed in GIF which can be utilized for various purposes with high-temperature heat at 750 to 950 $$^{circ}$$C. To increase economy of these HTGRs, JAEA has been upgrading the design method for the HTGR fuel, which can maintain their integrities at the burnup of three to four times higher than that of the conventional HTTR fuel. Design principles and specifications of various concepts of the high burnup HTGR fuels designed by JAEA are reported. As the latest results on post-irradiation examinations of the high burnup HTGR fuel progressing in a framework of international collaboration with Kazakhstan, irradiation shrinkage rate of the fuel compact as a function of fast neutron fluence was obtained at around 100 GWd/t. Furthermore, the future R&Ds needed for the high burnup HTGR fuel are described based on these experimental results.

Journal Articles

Conceptual design study of a high performance commercial HTGR for early introduction

Fukaya, Yuji; Mizuta, Naoki; Goto, Minoru; Ohashi, Hirofumi; Yan, X.

Nuclear Engineering and Design, 361, p.110577_1 - 110577_6, 2020/05

 Times Cited Count:1 Percentile:39.17(Nuclear Science & Technology)

Conceptual design study of a commercial High Temperature Gas-cooled Reactor (HTGR) for early introduction has been performed based on the cumulated experience in design, construction, and operation of the High Temperature engineering Test Reactor (HTTR) and design of the commercial Gas Turbine High Temperature Reactor 300 (GTHTR300). The power output is 165 MWt and the inlet and outlet coolant temperatures are 325$$^{circ}$$C and 750$$^{circ}$$C, respectively, to provide steam for industrial utilization. However, given a requirement for the reactor pressure vessel to be smaller even that of the 30 MWt HTTR, several challenging technical problems have to be dealt with to arrive in a high performance core design that provides extended fuel burnup, prolonged refueling period, improved fuel refueling scheme, improved fuel element and so on from the HTTR.

Journal Articles

Self-shielding effect of double heterogeneity for plutonium burner HTGR design

Fukaya, Yuji; Goto, Minoru; Ohashi, Hirofumi

Annals of Nuclear Energy, 138, p.107182_1 - 107182_9, 2020/04

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

The investigation on self-shielding effect of double heterogeneity for plutonium burner High Temperature Gas-cooled Reactor (HTGR) design has been performed. Plutonium burner HTGR designed in the previous study by using the advantage of double heterogeneity to control excess reactivity. In the present study, the mechanism of the self-shielding effect is elucidated by the analysis of burn-up calculation and reactivity decomposition based on exact perturbation theory. As a result, it is revealed that the characteristics of burn-up reactivity are determined by resonance cross section peak at 1 eV of $$^{240}$$Pu due to the surface term of background cross section, this is, the characteristics of neutron leakage from fuel lump and collision to a moderator. Moreover, significant spectrum shift is caused during the burn-up period, and it enhances reactivity worth of $$^{239}$$Pu and $$^{240}$$Pu in EOL.

Journal Articles

Research and development for safety and licensing of HTGR cogeneration system

Sato, Hiroyuki; Aoki, Takeshi; Ohashi, Hirofumi; Yan, X.

Nuclear Engineering and Design, 360, p.110493_1 - 110493_8, 2020/04

 Times Cited Count:2 Percentile:62.87(Nuclear Science & Technology)

JAEA has been conducting research and development with a central focus on the utilization of HTTR, the first HTGR in Japan, towards the realization of industrial use of nuclear heat. On the basis of licensing experience through the HTTR construction, JAEA initiated an activity to establish an international safety standard for licensing of commercial HTGR cogeneration systems fully taking into account safety features of HTGRs. We have developed a roadmap towards licensing of commercial HTGR cogeneration systems. A test plan using the HTTR to support the establishment of safety standards and safety analysis methods are also presented. In addition, we confirmed that a vessel cooling system, a passive air-cooled decay heat removal system, satisfies the safety requirement.

Journal Articles

Development of new corrosion test equipment simulating sulfuric acid decomposition gas environment in a thermochemical hydrogen production process

Hirota, Noriaki; Kasahara, Seiji; Iwatsuki, Jin; Imai, Yoshiyuki; Ohashi, Hirofumi; Yan, X.; Tachibana, Yukio

Zairyo To Kankyo, 68(6), p.137 - 142, 2019/06

New corrosion test equipment for high temperature gas of decomposed sulfuric acid was manufactured in order to ascertain flow rate of sulfuric acid in the piping, occurrence of sulfuric acid decomposition reaction in the equipment, and temperature distribution inside the furnace tube. The flow rate of the sulfuric acid solution was constantly measured using an ultrasonic flowmeter. The SO$$_{3}$$ concentration at the inlet of the test equipment was almost the same as that at the inlet of the sulfuric acid decomposer in the hydrogen production plant assuming a high-temperature gas cooled reactor hydrogen-power cogeneration system (GTHTR300C). On the other hand, during a test, leakage of sulfuric acid occurred from the fitting part at the outlet side. Hence the temperature distribution of the fitting part at the outlet side was investigated using fluid analysis. As a result, it was found that the temperature at the fitting was low enough to use fluorine joint grease when the distance was 0.05 m or more away from the outlet side pipe. An improved furnace tube was manufactured and the temperature was measured again at fitting part of the outlet side. The temperature was lower that the temperature limit of the joint grease and almost the same as the temperature distribution in the fluid analysis, and leakage of sulfuric acid has not occurred to date.

Journal Articles

Uncertainty analysis of toxic gas leakage accident in cogeneration high temperature gas-cooled reactor

Sato, Hiroyuki; Ohashi, Hirofumi

Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 8 Pages, 2019/05

To establish a probabilistic approach for assessment of toxic gas leakage accidents in a H$$_{2}$$ plant, the present study focusses on development of an uncertainty analysis method for toxic gas concentration in a control room. The method consists of 6 steps; (1) Identification of uncertainty factors, (2) derivation of variable parameters, (3) identification of uncertainties in variable parameters, (4) identification of important factors considering the sensitivity analysis results and expert opinions, (5) uncertainty propagation analysis, (6) assessment of uncertainty analysis results. The method is then applied to representative toxic gas leakage accidents in a H$$_{2}$$ plant by IS process coupled to the HTTR. The results obtained in the study leads us to the conclusion that the suggested method can successfully characterize and quantify uncertainties in the toxic gas concentration in control room.

Journal Articles

Research and development on high burnup HTGR fuels in JAEA

Ueta, Shohei; Mizuta, Naoki; Sasaki, Koei; Sakaba, Nariaki; Ohashi, Hirofumi; Yan, X.

Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 8 Pages, 2019/05

JAEA has been progressing to design HTGR fuels for not only small-type practical HTGRs but also VHTR proposed in GIF which can be utilized for various purposes with high-temperature heat at 750 to 950 $$^{circ}$$C. To increase economy of these HTGRs, JAEA has been upgrading the design method for the HTGR fuel, which can maintain their integrities at the burnup of three to four times higher than that of the conventional HTTR fuel. Design principles and specifications of various concepts of the high burnup HTGR fuels designed by JAEA are reported. As the latest results on post-irradiation examinations of the high burnup HTGR fuel progressing in a framework of international collaboration with Kazakhstan, irradiation shrinkage rate of the fuel compact as a function of fast neutron fluence was obtained at around 100 GWd/thm. Furthermore, the future R&Ds needed for the high burnup HTGR fuel are described based on these experimental results.

Journal Articles

Study of SiC-matrix fuel element for HTGR

Mizuta, Naoki; Aoki, Takeshi; Ueta, Shohei; Ohashi, Hirofumi; Yan, X.

Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 5 Pages, 2019/05

Enhancement of safety and cooling performance of fuel elements are desired for a commercial High Temperature Gas-cooled Reactor (HTGR). Applying sleeveless fuel elements and dual side directly cooling structures with oxidation resistant SiC-matrix fuel compact has a possibility of improving safety and cooling performance at the pin-in-block type HTGR. The irradiated effective thermal conductivity of a fuel compact is an important physical property for core thermal design of the pin-in-block type HTGR. In order to discuss the irradiated effective thermal conductivity of the SiC-matrix fuel compact which could improve the cooling performance of the reactor, the maximum fuel temperature during normal operation of the pin-in-block type HTGR with dual side directly cooling structures are analytically evaluated. From these results, the desired irradiated thermal conductivity of SiC matrix are discussed. In addition, the suitable fabrication method of SiC-matrix fuel compact is examined from viewpoints of the sintering temperature, the purity and the mass productivity.

Journal Articles

Uranium-based TRU multi-recycling with thermal neutron HTGR to reduce environmental burden and threat of nuclear proliferation

Fukaya, Yuji; Goto, Minoru; Ohashi, Hirofumi; Yan, X.; Nishihara, Tetsuo; Tsubata, Yasuhiro; Matsumura, Tatsuro

Journal of Nuclear Science and Technology, 55(11), p.1275 - 1290, 2018/11

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

To reduce environmental burden and thread of nuclear proliferation, multi-recycling fuel cycle with High Temperature Gas-cooled Reactor (HTGR) has been investigated. Those problems are solved by incinerating TRans Uranium (TRU) nuclides, which is composed of plutonium and Minor Actinoide (MA), and there is concept to realize TRU incineration by multi-recycling with Fast Breeder Reactor (FBR). In this study, multi-recycling is realized even with thermal reactor by feeding fissile uranium from outside of the fuel cycle instead of breeding fissile nuclide. In this fuel cycle, recovered uranium by reprocessing and natural uranium are enriched and mixed with recovered TRU by reprocessing and partitioning to fabricate fresh fuels. The fuel cycle was designed for a Gas Turbine High Temperature Reactor (GTHTR300), whose thermal power is 600 MW, including conceptual design of uranium enrichment facility. Reprocessing is assumed as existing Plutonium Uranium Redox EXtraction (PUREX) with four-group partitioning technology. As a result, it was found that the TRU nuclides excluding neptunium can be recycled by the proposed cycle. The duration of potential toxicity decaying to natural uranium level can be reduced to approximately 300 years, and the footprint of repository for High Level Waste (HLW) can be reduced by 99.7% compared with GTHTR300 using existing reprocessing and disposal technology. Suppress plutonium is not generated from this cycle. Moreover, incineration of TRU from Light Water Reactor (LWR) cycle can be performed in this cycle.

Journal Articles

Conceptual design of the steam reforming system for hydrogen production connected to HTTR

Iwatsuki, Jin; Ohashi, Hirofumi; Yan, X.

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

The HTTR is a 30MW, 950$$^{circ}$$C high temperature engineering test reactor built and operated on the site of the Oarai Research & Development Center of Japan Atomic Energy Agency (JAEA). In the framework of the HTTR project, JAEA has been conducting a research and development on the steam reforming system (CH$$_{4}$$ + H$$_{2}$$O = 3H$$_{2}$$ + CO). JAEA had constructed a mock-up test facility in 2002, and investigated transient behavior of the hydrogen production system and established system controllability. Based on the results and experience of above, the conceptual design of steam reforming system for hydrogen production connected to HTTR has been studied. The system condition was optimized considering the HTTR specification and the experience on the construction and the operation of the mock-up test facility. The hydrogen production system is heated with about 0.2MW transported from the HTTR to the hydrogen system via a helium loop. The system produces about 70 Nm$$^{3}$$/h hydrogen.

Journal Articles

Conceptual design study of a high performance commercial HTGR

Fukaya, Yuji; Mizuta, Naoki; Goto, Minoru; Ohashi, Hirofumi; Yan, X.

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

Conceptual design study of a high performance commercial HTGR has been performed at target output of 165MWt. Requirements for the HTGR are small-sized vessel for transportation, durability of vessel to irradiation damage, fuel reloading scheme to shorten the duration of reloading, low pressure drop fuel element, a small number of fuel enrichments, and so on. To satisfy the requirement, we investigated the core configuration, shielding and reflector configuration, fuel reloading scheme. As a result, we completed the design with the vessel diameter of 4.5m, which can be transported by any means, such as, by load, rail, ship, and air plane, and high load factor over 90%.

Journal Articles

Conceptual plant system design study of an experimental HTGR upgraded from HTTR

Ohashi, Hirofumi; Goto, Minoru; Ueta, Shohei; Sato, Hiroyuki; Fukaya, Yuji; Kasahara, Seiji; Sasaki, Koei; Mizuta, Naoki; Yan, X.; Aoki, Takeshi*

Proceedings of 9th International Topical Meeting on High Temperature Reactor Technology (HTR 2018) (USB Flash Drive), 6 Pages, 2018/10

Conceptual design study of an experimental HTGR is performed to upgrade the plant system from Japanese High Temperature engineering Test Reactor (HTTR) to a commercial HTGR. Safety systems of HTTR are upgraded to demonstrate the commercial HTGR concept, such as a passive reactor cavity cooling system, a confinement, etc. An intermediate heat exchanger (IHX) is replaced by a steam generator (SG) for a process heat supply to demonstrate the technology for a commercial use. This paper describes the conceptual design study results of the plant system of the experimental HTGR.

182 (Records 1-20 displayed on this page)