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Journal Articles

New market opened up by advanced nuclear reactors (Chapter 3, 4, 5, 7)

Kamide, Hideki; Kawasaki, Nobuchika; Hayafune, Hiroki; Kubo, Shigenobu; Chikazawa, Yoshitaka; Maeda, Seiichiro; Sagayama, Yutaka; Nishihara, Tetsuo; Sumita, Junya; Shibata, Taiju; et al.

Jisedai Genshiro Ga Hiraku Atarashii Shijo; NSA/Commentaries, No.28, p.14 - 36, 2023/10

Developments of next generation nuclear reactors, e.g., Fast Reactor, and High Temperature Gas cooled Reactor, are in progress. They can contribute to markets of electricity and industrial heat utilization in the world including Japan. Here, current status of reactor developments in Japan and also situation in the world are summarized, especially for activities of Generation IV International Forum (GIF), developments of Fast Reactor and High Temperature Gas cooled Reactor in Japan, and SMR movements in the world.

JAEA Reports

Operation, test, research and development of the High Temperature Engineering Test Reactor (HTTR) (FY2021)

Department of HTTR

JAEA-Review 2023-016, 82 Pages, 2023/09

JAEA-Review-2023-016.pdf:2.31MB

The High Temperature Engineering Test Reactor (HTTR) is the first Japanese High Temperature Gas-cooled Reactor (HTGR) with 30MW in thermal power and 950$$^{circ}$$C of maximum outlet coolant temperature that is constructed by the Japan Atomic Energy Agency located at Oarai-machi, Higashiibaraki-gun, Ibaraki-ken, Japan. The purpose of the HTTR is establishment of basic HTGR technologies, demonstration of HTGR safety characteristics and so on. The HTTR has had a lot of experience of HTGRs' operation and maintenance throughout rated power operations, safety demonstration tests, long-term high temperature operations and demonstration tests relevant to HTGRs' R&Ds. In the fiscal year 2021, as the HTTR completed activities to conform to the New Regulatory Requirements of Nuclear Regulation Authority, The HTTR restarted since the 2011 off the Pacific coast of Tohoku Earthquake and carried out the Loss-of-forced cooling test without Vessel Cooling System (VCS) operational at 9MW (Three gas circulators trip and VCS is stopped.) as the safety demonstration test. This report summarizes the activities carried out in the fiscal year 2021, which were the situation of the New Regulatory Requirements screening of the HTTR, the operation and maintenance of the HTTR, R&Ds relevant to commercial-scale HTGRs, the international cooperation on HTGRs and so on.

JAEA Reports

Study of fabrication of SiC-matrixed fuel compact for HTGR

Kawano, Takahiro*; Mizuta, Naoki; Ueta, Shohei; Tachibana, Yukio; Yoshida, Katsumi*

JAEA-Technology 2023-014, 37 Pages, 2023/08

JAEA-Technology-2023-014.pdf:2.35MB

Fuel compact for High Temperature Gas-cooled Reactor (HTGR) is fabricated by calcinating a matrix consisting of graphite and binder with the coated fuel particle. The SiC-matrixed fuel compact uses a new matrix made of silicon carbide (SiC) replacing the conventional graphite. Applying the SiC-matrixed fuel compact for HTGRs is expected to improve their performance such as power densities. In this study, the sintering conditions for applying SiC as the matrix of fuel compacts for HTGR are selected, and the density and thermal conductivity of the prototype SiC are measured.

JAEA Reports

Report of summer holiday practical training on 2022

Ishitsuka, Etsuo; Ho, H. Q.; Kitagawa, Kanta*; Fukuda, Takahito*; Ito, Ryo*; Nemoto, Masaya*; Kusunoki, Hayato*; Nomura, Takuro*; Nagase, Sota*; Hashimoto, Haruki*; et al.

JAEA-Technology 2023-013, 19 Pages, 2023/06

JAEA-Technology-2023-013.pdf:1.75MB

Eight people from five universities participated in the 2022 summer holiday practical training with the theme of "Technical development on HTTR". The participants practiced the feasibility study for nuclear battery, the burn-up analysis of HTTR core, the feasibility study for $$^{252}$$Cf production, the analysis of behavior on loss of forced cooling test, and the thermal-hydraulic analysis near reactor pressure vessel. In the questionnaire after this training, there were impressions such as that it was useful as a work experience, that some students found it useful for their own research, and that discussion with other university students was a good experience. These impressions suggest that this training was generally evaluated as good.

JAEA Reports

Development of wide range monitor for HTTR; Improvement for heat resistance performance against heat cycle

Kozawa, Takayuki; Suganuma, Takuro; Homma, Fumitaka; Higashimura, Keisuke*; Ukai, Takayuki*; Saito, Kenji

JAEA-Technology 2023-007, 24 Pages, 2023/06

JAEA-Technology-2023-007.pdf:2.24MB

To improve the reliability of the HTTR wide range monitor in a high-temperature environment, structural changes of the wide range monitor were investigated. It was clear that the structure for directly joins of the MI cable core wire and metal tube instead of the joins with lead wire is the most reliable method with shortest way. From a result of the thermal cycle tests and high temperature endurance tests for a mock-up connecting this connection parts, it was clear that the soundness of the connection part was maintained under the usage conditions of the HTTR.

JAEA Reports

Differential pressure rise event for filters of HTTR primary helium gas circulators, 1; Investigation of differential pressure rise event

Nemoto, Takahiro; Arakawa, Ryoki; Kawakami, Satoru; Nagasumi, Satoru; Yokoyama, Keisuke; Watanabe, Masashi; Onishi, Takashi; Kawamoto, Taiki; Furusawa, Takayuki; Inoi, Hiroyuki; et al.

JAEA-Technology 2023-005, 33 Pages, 2023/05

JAEA-Technology-2023-005.pdf:5.25MB

During shut down of the HTTR (High Temperature engineering Test Reactor) RS-14 cycle, an increasing trend of filter differential pressure for the helium gas circulator was observed. In order to investigate this phenomenon, the blower of the primary helium purification system was disassembled and inspected. As a result, it is clear that the silicon oil mist entered into the primary coolant due to the deterioration of the charcoal filter performance. The replacement and further investigation of the filter are planning to prevent the reoccurrence of the same phenomenon in the future.

Journal Articles

Improvement of cooling performance of reactor pressure vessel using passive cooling

Banno, Masaki*; Funatani, Shumpei*; Takamatsu, Kuniyoshi

Proceedings of 30th International Conference on Nuclear Engineering (ICONE30) (Internet), 7 Pages, 2023/05

A fundamental study on the safety of a passive cooling system for the RPV with radiative cooling is conducted. The object of this study is to demonstrate that passive RPV cooling system with radiative cooling is extremely safe and reliable even in the event of natural disasters. Therefore, an experimental apparatus, which is about 1/20 scale of the actual cooling system, was fabricated with several stainless steel containers. The surface of the heating element in the experimental apparatus simulates the surface of the RPV, and the heating element generates natural convection and radiation. A comparison of the Grashof number between the actual cooling system and the experimental apparatus confirmed that both were turbulent, and the experimental results as a scale model are valuable. Moreover, the experimental results confirmed that the heat generated from the surface of the RPV during the rated operation can be removed.

Journal Articles

Comparison on safety features among HTGR's Reactor Cavity Cooling Systems (RCCSs)

Takamatsu, Kuniyoshi; Funatani, Shumpei*

Proceedings of 2023 International Congress on Advanced in Nuclear Power Plants (ICAPP 2023) (Internet), 17 Pages, 2023/04

The objectives of this study are as follows: to understand the characteristics, degree of passive safety features for heat removal were compared for RCCSs based on atmospheric radiation and based on atmospheric natural circulation under the same conditions. Therefore, the authors concluded that the proposed RCCS based on atmospheric radiation has the advantage that the temperature of the RPV can be stably maintained against disturbances in the outside air (ambient air). Moreover, methodology to utilize all the heat emitted from the RPV surface for increasing the degree of waste-heat utilization was discussed.

Journal Articles

Evaluation of corrosion resistance and surface film analysis after corrosion testing of materials coated by chemical densified coating method under boiling sulfuric acid environment

Hirota, Noriaki; Funamoto, Kodai*; Tachibana, Yukio

Zairyo, 72(3), p.255 - 261, 2023/03

For the purpose of developing metallic materials with excellent corrosion resistance under boiling sulfuric acid environment, the coated materials were evaluated for their corrosion resistance and the differences in surface morphology were investigated. As a result, the corrosion resistance of SUS304 coated and sintered eight times by chemical densified coating method (S-ZAC) was maintained at the point after 12h corrosion test, but the corrosion rate rapidly increased after 100h corrosion test. The cross-sectional microstructural analysis of the specimens showed that only a small amount of SiO$$_{2}$$ remained on the surface, while Cr$$_{2}$$O$$_{3}$$ completely disappeared. The mechanism of film delamination in S-ZAC is assumed to be due to the thermal expansion caused by heating, which resulted in curvature of the thick film and cracks at the Cr$$_{2}$$O$$_{3}$$ and SiO$$_{2}$$ interfaces. On the other hand, SUS304 coated with higher density of Cr$$_{2}$$O$$_{3}$$ by repeating the coating and sintering eleven times (MS-ZAC) showed excellent corrosion resistance as well as SiC even after 100h corrosion test. The results of cross-sectional microstructuCr$$_{2}$$O$$_{3}$$ particle layer, in addition to the thinning of the entire film.

Journal Articles

Evaluation of power distribution calculation of the very high temperature reactor critical assembly (VHTRC) with Monte Carlo MVP3 code

Simanullang, I. L.*; Nakagawa, Naoki*; Ho, H. Q.; Nagasumi, Satoru; Ishitsuka, Etsuo; Iigaki, Kazuhiko; Fujimoto, Nozomu*

Annals of Nuclear Energy, 177, p.109314_1 - 109314_8, 2022/11

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

Journal Articles

Present status of JAEA's R&D toward HTGR deployment

Shibata, Taiju; Nishihara, Tetsuo; Kubo, Shinji; Sato, Hiroyuki; Sakaba, Nariaki; Kunitomi, Kazuhiko

Nuclear Engineering and Design, 398, p.111964_1 - 111964_4, 2022/11

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

Japan Atomic Energy Agency (JAEA) has been promoting the research and development (R&D) of High Temperature Gas-cooled Reactor (HTGR). R&D on reactor technologies is carried out by using High Temperature engineering Test Reactor (HTTR). The HTTR was resumed without significant reinforcements in 2021. On January 2022, a safety demonstration test under the OECD/NEA LOFC project was carried out. JAEA is promoting R&D on a carbon-free hydrogen production by thermochemical water splitting Iodine-Sulfur process (IS process). JAEA conducts design study for various HTGR systems toward commercialization. A new test program about demonstration of hydrogen production by the HTTR was launched. Steam methane reforming hydrogen production system was selected for the first demonstration by 2030.

Journal Articles

Study on heat transfer characteristics of reactor cavity cooling system using radiation

Banno, Masaki*; Funatani, Shumpei*; Takamatsu, Kuniyoshi

Yamanashi Koenkai 2022 Koen Rombunshu (CD-ROM), 6 Pages, 2022/10

A fundamental study on the safety of a passive cooling system for the reactor pressure vessel (RPV) with radiative cooling is conducted. The object of this study is to demonstrate that passive RPV cooling system with radiative cooling is extremely safe and reliable even in the event of natural disasters. Therefore, an experimental apparatus, which is about 1/20 scale of the actual cooling system, was fabricated with several stainless steel containers. The surface of the heating element in the experimental apparatus simulates the surface of the RPV, and the heating element generates natural convection and radiation. As a result of the experiments, we succeeded in visualizing the natural convection in the experimental apparatus in detail.

JAEA Reports

Operation, test, research and development of the High Temperature Engineering Test Reactor (HTTR) (FY2020)

Department of HTTR

JAEA-Review 2022-018, 90 Pages, 2022/09

JAEA-Review-2022-018.pdf:2.85MB

The High Temperature Engineering Test Reactor (HTTR) is the first High Temperature Gas-cooled Reactor (HTGR) constructed in Japan at the Oarai Research and Development Institute of the Japan Atomic Energy Agency with 30MW in thermal power and 950$$^{circ}$$C of maximum outlet coolant temperature. The purpose of the HTTR is establishment of basic HTGR technologies, demonstration of HTGR safety characteristics and so on. The HTTR has had a lot of experience of HTGRs' operation and maintenance throughout rated power operations, safety demonstration tests, long-term high temperature operations and demonstration tests relevant to HTGRs' R&Ds. In the fiscal year 2020, we continued to make effort to restart of the HTTR that stopped since the 2011 off the Pacific coast of Tohoku Earthquake. On 3rd June 2020, we obtained permission to the New Regulatory Requirements which make great progress toward the restart of the HTTR. This report summarizes the activities carried out in the fiscal year 2020, which were the situation of the New Regulatory Requirements screening of the HTTR, the operation and maintenance of the HTTR, R&Ds relevant to commercial-scale HTGRs, the international cooperation on HTGRs and so on.

Journal Articles

Calculation of shutdown gamma distribution in the high temperature engineering test reactor

Ho, H. Q.; Ishii, Toshiaki; Nagasumi, Satoru; Ono, Masato; Shimazaki, Yosuke; Ishitsuka, Etsuo; Goto, Minoru; Simanullang, I. L.*; Fujimoto, Nozomu*; Iigaki, Kazuhiko

Nuclear Engineering and Design, 396, p.111913_1 - 111913_9, 2022/09

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

Journal Articles

MCNP6 calculation of neutron flux map in the HTTR during normal operation

Ho, H. Q.; Ishitsuka, Etsuo; Iigaki, Kazuhiko

Recent Contributions to Physics, 82(3), p.16 - 20, 2022/09

Journal Articles

Study on the effect of long-term high temperature irradiation on TRISO fuel

Shaimerdenov, A.*; Gizatulin, S.*; Dyussambayev, D.*; Askerbekov, S.*; Ueta, Shohei; Aihara, Jun; Shibata, Taiju; Sakaba, Nariaki

Nuclear Engineering and Technology, 54(8), p.2792 - 2800, 2022/08

 Times Cited Count:4 Percentile:90.16(Nuclear Science & Technology)

JAEA Reports

Calculation of nuclear core parameters for HTTR; Report of summer holiday practical training 2021

Isogawa, Hiroki*; Naoi, Motomasa*; Yamasaki, Seiji*; Ho, H. Q.; Katayama, Kazunari*; Matsuura, Hideaki*; Fujimoto, Nozomu*; Ishitsuka, Etsuo

JAEA-Technology 2022-015, 18 Pages, 2022/07

JAEA-Technology-2022-015.pdf:1.37MB

As a summer holiday practical training 2021, the impact of 10 years long-term shutdown on critical control rod position of the HTTR and the delayed neutron fraction ($$beta$$$$_{rm eff}$$) of the VHTRC-1 core were investigated using Monte-Carlo MVP code. As a result, a long-term shutdown of 10 years caused the critical control rods of the HTTR to withdraw about 4.0$$pm$$0.8 cm compared to 3.9 cm in the experiment. The change in critical control rods position of the HTTR is due to the change of some fission products such as $$^{241}$$Pu, $$^{241}$$Am, $$^{147}$$Pm, $$^{147}$$Sm, $$^{155}$$Gd. Regarding the $$beta$$$$_{rm eff}$$ calculation of the VHTRC-1 core, the $$beta$$$$_{rm eff}$$ value is underestimate of about 10% in comparison with the experiment value.

Journal Articles

Improving the safety of the high temperature gas-cooled reactor "HTTR" based on Japan's new regulatory requirements

Hamamoto, Shimpei; Shimizu, Atsushi; Inoi, Hiroyuki; Tochio, Daisuke; Homma, Fumitaka; Sawahata, Hiroaki; Sekita, Kenji; Watanabe, Shuji; Furusawa, Takayuki; Iigaki, Kazuhiko; et al.

Nuclear Engineering and Design, 388, p.111642_1 - 111642_11, 2022/03

 Times Cited Count:0 Percentile:33.72(Nuclear Science & Technology)

Following the Fukushima Daiichi Nuclear Power Plant accident in 2011, the Japan Atomic Energy Agency adapted High-Temperature engineering Test Reactor (HTTR) to meet the new regulatory requirements that began in December 2013. The safety and seismic classifications of the existing structures, systems, and components were discussed to reflect insights regarding High Temperature Gas-cooled Reactors (HTGRs) that were acquired through various HTTR safety tests. Structures, systems, and components that are subject to protection have been defined, and countermeasures to manage internal and external hazards that affect safety functions have been strengthened. Additionally, measures are in place to control accidents that may cause large amounts of radioactive material to be released, as a beyond design based accident. The Nuclear Regulatory Commission rigorously and appropriately reviewed this approach for compliance with the new regulatory requirements. After nine amendments, the application to modify the HTTR's installation license that was submitted in November 2014 was approved in June 2020. This response shows that facilities can reasonably be designed to meet the enhanced regulatory requirements, if they reflect the characteristics of HTGRs. We believe that we have established a reference for future development of HTGR.

Journal Articles

Design of a portable backup shutdown system for the high temperature gas cooled reactor

Hamamoto, Shimpei; Ho, H. Q.; Iigaki, Kazuhiko; Goto, Minoru; Shimazaki, Yosuke; Sawahata, Hiroaki; Ishitsuka, Etsuo

Nuclear Engineering and Design, 386, p.111564_1 - 111564_8, 2022/01

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

The experience of Fukushima Daiichi Nuclear Power Plant accident caused by the great earthquake that occurred in eastern Japan in 2011 showed the importance of preparing for the loss of function of the engineered safety features. Increasing the strength of equipment to prevent loss of function in an accident is effective, but the possibility of loss of function remains. Therefore, it is important to have an alternative to lost functions in order to put the accident under control early. Thus, this study designed an alternative shutdown system, namely a portable backup shutdown system (PBSS), to make countermeasures in the event of a loss of shutdown function more robust without impairing economic efficiency of the High Temperature Gas-cooled Reactor (HTGR). The PBSS is portable and capable of being installed manually so that it can operate in a total loss of off-site electricity. Various neutron absorber materials for the PBSS were also considered from the viewpoints of technical and cost-effective properties. As results of optimization, the boron nitride (BN) was selected as it shows a good neutronic property as well as a reasonable cost in comparison with other materials.

JAEA Reports

Operation, test, research and development of the High Temperature Engineering Test Reactor (HTTR) (FY2019)

Department of HTTR

JAEA-Review 2021-017, 81 Pages, 2021/11

JAEA-Review-2021-017.pdf:2.53MB

The High Temperature Engineering Test Reactor (HTTR) is the first High-Temperature Gas cooled Reactor (HTGR) constructed in Japan at the Oarai Research and Development Institute of the Japan Atomic Energy Agency with 30MW in thermal power and 950$$^{circ}$$C of outlet coolant temperature. The purpose of the HTTR is to establish and upgrade basic technologies for HTGRs. The HTTR has accumulated a lot of experience of HTGRs' operation and maintenance up to the present time throughout rated power operations, safety demonstration tests, long-term high temperature operations and demonstration tests relevant to HTGRs' R&Ds. In the fiscal year 2019, we continued to make effort to restart operations of the HTTR that stopped since the 2011 off the Pacific coast of Tohoku Earthquake. It is necessary for the HTTR reoperation to prove conformity with the new regulatory requirements for research reactors enacted in December 2013. So we might cope with government agency to pass the inspection of application document for the HTTR licensing. This report summarizes the activities carried out in the fiscal year 2019, which were the situation of the new regulatory requirements screening of the HTTR, the operation and maintenance of the HTTR, R&Ds relevant to commercial-scale HTGRs, the international cooperation on HTGRs and so on.

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