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Fuyushima, Takumi; Sayato, Natsuki; Otsuka, Kaoru; Endo, Yasuichi; Tobita, Masahiro*; Takemoto, Noriyuki
JAEA-Testing 2024-008, 38 Pages, 2025/03
JAEA-Testing-2024-008.pdf:2.37MB
In Japan Materials Testing Reactor (JMTR), irradiation tests had been conducted by loading specimens into capsules for irradiating fuels and materials. The thermal design calculation of capsules is significant to irradiate various types of specimens at the target temperature. The decommissioning plan of JMTR was approved in March 2021, and the Department of Waste Management and Decommissioning Technology Development is currently working on irradiation plans by foreign testing reactors as an alternative for JMTR. A one-dimensional thermal calculation code "GENGTC", which was developed at the Oak Ridge National Laboratory in U.S., is used for capsule design and irradiation tests. GENGTC has been repeatedly improved as improvements of computer performance, but there were some defects in calculation function. Therefore, we investigated the cause of the problem and changed the program from the currently used FORTRAN77 language program to a Visual Basic language program that uses the macro calculation function of Excel. In addition, the program was improved to make it easier to use the calculation code.
Nagata, Hiroshi; Kochiyama, Mami; Chinone, Marina; Sugaya, Naoto; Nishimura, Arashi; Ishikawa, Joji; Sakai, Akihiro; Ide, Hiroshi
JAEA-Data/Code 2024-016, 44 Pages, 2025/03
JAEA-Data-Code-2024-016.pdf:3.54MB
The elemental composition of the structural materials of nuclear reactor facilities is used as one of the important parameters in activation calculations that are evaluated when formulating decommissioning plans. Regarding the elemental composition of aluminum alloys and other materials used as structural materials for test and research reactors, sufficient data is not available regarding elements other than the major elements. For this reason, samples were collected from aluminum alloy, beryllium, hafnium, and other materials that have been used as the main structural materials of JMTR (Japan Materials Testing Reactor), and their elemental compositions were analyzed. This report summarizes the elemental composition data of 78 elements obtained in FY2023.
Sayato, Natsuki; Otsuka, Kaoru; Fuyushima, Takumi; Endo, Yasuichi; Otsuka, Noriaki; Kitagishi, Shigeru; Tobita, Masahiro*; Isozaki, Futoshi*; Matsumoto, Satoshi*; Takemoto, Noriyuki
JAEA-Technology 2024-016, 247 Pages, 2025/02
JAEA-Technology-2024-016.pdf:28.43MB
Japan Materials Testing Reactor (JMTR, 50MW) was selected as a project to be subsidized by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) for the "Establishment of an International Research and Development Center through Advanced Utilization of the World's Most Advanced Research Reactor". As part of this project, JMTR has installed "LWR Water Environment Simulation Tests" since 2010. This facility can control temperature, pressure, and water quality (dissolved oxygen, dissolved hydrogen, etc.) to simulate the water environment of light water reactors (BWR and PWR) and perform neutron irradiation of in-core structural materials, etc. In addition, this facility is also designed for PWR conditions. Chemical injection system for adding boron and lithium was added to the facility for PWR conditions. After the equipment was installed, test operation was carried out to confirm the performance of the facility. This report summarizes the establishment and test operation of LWR Water Environment Simulation Tests after the establishment.
Onishi, Takashi; Koyama, Shinichi*; Yokoyama, Keisuke; Morishita, Kazuki; Watanabe, Masashi; Maeda, Shigetaka; Yano, Yasuhide; Oki, Shigeo
Nuclear Engineering and Design, 432, p.113755_1 - 113755_17, 2025/02
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)Hirota, Noriaki; Nakano, Hiroko; Takeda, Ryoma; Ide, Hiroshi; Tsuchiya, Kunihiko; Kobayashi, Yoshinao*
Zairyo No Kagaku To Kogaku, 61(6), p.248 - 252, 2024/12
A comparative analysis of the 0.2 % yield stress in SUS304L stainless steel revealed that lower strain rates and higher temperatures significantly reduce yield stress. Grain refinement from 68.6 
m to 0.59 m minimally impacted the rate of yield stress reduction at slower strain rates. However, finer grains showed a decrease in yield stress at reactor operating temperature compared to room temperature. In slow strain rate tests under conditions promoting intragranular stress corrosion cracking (SCC), SUS304L with grain sizes of 28.4 m or smaller exhibited similar fracture strains comparable to those at reactor operating temperatures, whereas coarse-grained SUS304L showed reduced fracture strain. Microstructural analysis showed that in smaller grains, over 87 % of the fracture surface was ductile. In particular, SUS304L with 0.59 m grains exhibited a higher presence of {111} / 
3 boundaries, which decreased with grain growth. These results indicate that grain refinement will suppress intragranular SCC by slowing corrosion progression through increased {111} / 3 boundaries.
Machida, Masahiko; Yamada, Susumu; Kim, M.; Tanaka, Satoshi*; Tobita, Yasuhiro*; Iwata, Ayako*; Aoki, Yuto; Aoki, Kazuhisa; Yanagisawa, Kenichi*; Yamaguchi, Takashi; et al.
RIST News, (70), p.3 - 22, 2024/09
Inside the Fukushima Daiichi Nuclear Power Plant (1F), there are many locations with high radiation levels due to contamination by radioactive materials that leaked from the reactor. These pose a significant obstacle to the smooth progress of decommissioning work. To help solve this issue, the Japan Atomic Energy Agency (JAEA), under a subsidy from the Ministry of Economy, Trade, and Industry's decommissioning and contaminated water management project, is conducting research and development on digital technologies to improve the radiation environment inside the decommissioning site. This project, titled "Development of Technology to Improve the Environment Inside Reactor Buildings (Enhancing Digital Technology for Environment and Source Distribution to Reduce Radiation Exposure)," began in April of FY 2023. In this project, the aim is to develop three interconnected systems: FrontEnd, Pro, and BackEnd. The FrontEnd system, based on the previously developed 3D-ADRES-Indoor (prototype) from FY 2021-2022, will be upgraded to a high-speed digital twin technology usable on-site. The Pro system will carry out detailed analysis in rooms such as the new office building at 1F, while the BackEnd system will serve as a database to centrally manage the collected and analyzed data. This report focuses on the FrontEnd system, which will be used on-site. After point cloud measurement, the system will quickly create a 3D mesh model, estimate the radiation source from dose rate measurements, and refine the position and intensity of the estimated source using recalculation techniques (re-observation instructions and re-estimation). The results of verification tests conducted on Unit 5 are also presented. Furthermore, the report briefly discusses the future research and development plans for this project.
Kawabata, Kuniaki; Imabuchi, Takashi; Shirasaki, Norihito*; Suzuki, Soichiro; Ito, Rintaro; Aoki, Yuto; Omori, Takazumi
ROBOMECH Journal (Internet), 11, p.11_1 - 11_11, 2024/09
Ishida, Reiya; Sonobe, Hiroshi; Kimura, Akihiro
JAEA-Review 2024-030, 75 Pages, 2024/08
JAEA-Review-2024-030.pdf:8.53MB
Department of JMTR Hot Laboratory (HL) had been construction since 1967 (concrete and lead cells have been in service since 1971 and steel cells since 1982). Because the HL is old, there is a high possibility that asbestos is used in heat insulation material wrapped around the piping installed in the HL. If asbestos is contained in that of such pipes, it may be dispersed into the air during repair, remodeling, or removal of such pipes, causing lung cancer, mesothelioma, or other health problems to workers. Therefore, it is also important to understand the status of asbestos use in the facility. The HL has been investigating the presence of asbestos in heat insulation material wrapped around piping in several systems installed in the facility. As a result, asbestos was detected in some of heat insulation material. This report describes the results of the asbestos survey conducted so far.
Nakano, Hiroko; Fujinami, Kyoko; Yamaura, Takayuki; Kawakami, Jun; Hanakawa, Hiroki
JAEA-Review 2023-036, 33 Pages, 2024/03
JAEA-Review-2023-036.pdf:2.47MB
A practical training course using the JMTR (Japan Materials Testing Reactor) and other research infrastructures was held from November 29 to December 2 in 2021 for Asian young researchers and engineers. This course was adopted as International Youth Exchange Program in Science (SAKURA SCIENCE Exchange Program) which is the project of the Japan Science and Technology Agency, and this course aims to enlarge the number of high-level nuclear researchers/engineers in Asian countries which are planning to introduce a nuclear power plant, and to promote the use of facilities in future. In this year, from the viewpoint of preventing the spread of COVID-19 infection, it was decided to hold the event online. 53 young researchers and engineers joined the course from 6 countries. In FY2022, training programs with invitations were held due to the easing of restrictions on entry into Japan from overseas. 7 young researchers and engineers from4 Asian countries participated in the training from February 1 to 10, 2023. The common curriculum in the training course of FY2021 and FY2022 included lectures on nuclear energy, irradiation testing, safety management, JMTR decommissioning plan, etc. In the online session, conducted in FY2021, information exchange on the energy situation in each country was conducted. On-site training conducted in FY2022, included practical training on operation using simulations, environmental monitoring, etc. and facility tours of the JMTR, etc. Many participants could join the online training course, they created a diversity of expertise and made lively discussions during the information exchange. On-site training, while limited in number of participants, provided a good opportunity for personnel exchange through practical training and face-face communication. It is desirable to hold on-site training as long as circumstances permit. This report summarizes the training conducted in FY2021 and FY2022.
Nagata, Hiroshi; Omori, Takazumi; Maeda, Eita; Otsuka, Kaoru; Nakano, Hiroko; Hanakawa, Hiroki; Ide, Hiroshi
JAEA-Review 2023-033, 40 Pages, 2024/01
JAEA-Review-2023-033.pdf:1.39MB
Japan Materials Testing Reactor (JMTR) was decided as a one of decommission facilities in April 2017. In order to submit the decommissioning plan to the Nuclear Regulation Authority, the type of accident assumed in the first stage of the decommissioning plan was selected, and the public exposure dose was evaluated. A fuel handling accident and a fire accident during storage of waste were selected as assumed accidents in the first stage of the decommissioning plan. An evaluation of the public exposure dose from the radioactive materials released into the atmosphere due to these accidents was estimated to be a maximum of 0.019 mSv (due to a fire accident during storage of waste). This estimated value was found to be sufficiently smaller than the judging criteria (5 mSv), and not to pose a significant risk of radiation exposure to the general public.
Fuyushima, Takumi; Takabe, Yugo; Sayato, Natsuki; Kimura, Akihiro; Takemoto, Noriyuki
The IV International Scientific Forum "Nuclear Science and Technologies"; AIP Conference Proceedings 3020, p.040007_1 - 040007_6, 2024/01
We studied irradiation tests of structural materials simulating fast reactor conditions in JMTR. We fabricated capsules that can simulate fast reactor irradiation in JMTR by using He/dpa ratio as index. To simulate fast reactor, cadmium, which shield thermal neutrons, was placed inside the capsule to adjust the neutron spectrum. According to the result of irradiation tests by neutron spectrum adjusting capsule, we confirmed that it can simulate the He/dpa ratio of fast reactor. Currently, since it is impossible to conduct irradiation tests in Japan, a plan is underway to partly replace the irradiation function of JMTR with overseas reactors. The alternative irradiation will be carried out by succeeding and developing the irradiation technology accumulated in the JMTR, and as a part of this, a trial of such irradiation in which the neutron spectrum is adjusted is under consideration.
Machida, Masahiko; Yamada, Susumu; Kim, M.; Okumura, Masahiko; Miyamura, Hiroko; Shikaze, Yoshiaki; Sato, Tomoki*; Numata, Yoshiaki*; Tobita, Yasuhiro*; Yamaguchi, Takashi; et al.
RIST News, (69), p.2 - 18, 2023/09
The contamination of radioactive materials leaked from the reactor has resulted in numerous hot spots in the Fukushima Daiichi Nuclear Power Station (1F) building, posing obstacles to its decommissioning. In order to solve this problem, JAEA has conducted research and development of the digital technique for inverse estimation of radiation source distribution and countermeasures against the estimated source in virtual space for two years from 2021 based on the subsidy program "Project of Decommissioning and Contaminated Water Management" performed by the funds from the Ministry of Economy, Trade and Industry. In this article, we introduce the results of the project and the plan of the renewal project started in April 2023. For the former project, we report the derivative method for LASSO method considering the complex structure inside the building and the character of the source and show the result of the inverse estimation using the method in the real reactor building. Moreover, we explain the platform software "3D-ADRES-Indoor" which integrates these achievements. Finally, we introduce the plan of the latter project.
Tsuchiya, Kunihiko
Nihon Genshiryoku Gakkai-Shi ATOMO, 65(6), p.393 - 397, 2023/06
no abstracts in English
Takabe, Yugo; Otsuka, Noriaki; Fuyushima, Takumi; Sayato, Natsuki; Inoue, Shuichi; Morita, Hisashi; Jaroszewicz, J.*; Migdal, M.*; Onuma, Yuichi; Tobita, Masahiro*; et al.
JAEA-Technology 2022-040, 45 Pages, 2023/03
JAEA-Technology-2022-040.pdf:6.61MB
Because of the decommission of the Japan Materials Testing Reactor (JMTR), the domestic neutron irradiation facility, which had played a central role in the development of innovative nuclear reactors and the development of technologies to further improve the safety, reliability, and efficiency of light water reactors, was lost. Therefore, it has become difficult to pass on the operation techniques of the irradiation test reactors and irradiation technologies, and to train human resources. In order to cope with these issues, we conducted a study on the implementation of irradiation tests using overseas reactors as neutron irradiation sites as an alternative method. Based on the "Arrangement between the National Centre for Nuclear Research and the Japan Atomic Energy Agency for Cooperation in Research and Development on Testing Reactor," the feasibility of conducting an irradiation test at the MARIA reactor (30 MW) owned by the National Centre for Nuclear Research (NCBJ) using the temperature control system, which is one of the JMTR irradiation technologies, was examined. As a result, it was found that the irradiation test was possible by modifying the ready-made capsule manufactured in accordance with the design and manufacturing standards of the JMTR. After the modification, a penetration test, an insulation continuity test, and an operation test in the range of room temperature to 300
C, which is the operating temperature of the capsule, were conducted and favorable results were obtained. We have completed the preparations prior to transport to the MARIA reactor.
Machida, Masahiko; Shi, W.*; Yamada, Susumu; Miyamura, Hiroko; Yoshida, Toru*; Hasegawa, Yukihiro*; Okamoto, Koji; Aoki, Yuto; Ito, Rintaro; Yamaguchi, Takashi; et al.
Proceedings of Waste Management Symposia 2023 (WM2023) (Internet), 11 Pages, 2023/02
Nakano, Hiroko; Nishikata, Kaori; Nagata, Hiroshi; Ide, Hiroshi; Hanakawa, Hiroki; Kusunoki, Tsuyoshi
JAEA-Review 2022-073, 23 Pages, 2023/01
JAEA-Review-2022-073.pdf:2.02MB
A practical training course using the JMTR (Japan Materials Testing Reactor) and other research infrastructures was held from July 24th to July 31st in 2019 for Asian young researchers and engineers. This course was adopted as Japan-Asia Youth Exchange Program in Science (SAKURA Exchange Program in Science) which is the project of the Japan Science and Technology Agency, and this course aims to enlarge the number of high-level nuclear researchers/engineers in Asian countries which are planning to introduce a nuclear power plant, and to promote the use of facilities in future. In this year, 12 young researchers and engineers joined the course from 6 countries. This course consists of lectures, which are related to irradiation test research, safety management of nuclear reactors, nuclear characteristics of the nuclear reactors, etc., practical training such as practice of research reactor operation using simulator and technical tour of nuclear facilities on nuclear energy. The content of this course in FY 2019 is reported in this paper.
Okada, Yuji; Magome, Hirokatsu; Matsui, Yoshinori
JAEA-Technology 2022-014, 113 Pages, 2022/09
JAEA-Technology-2022-014.pdf:15.79MB
Material irradiation test system had been newly installed in JMTR (Japan Materials Testing Reactor) with taking 5 years which was from 2008 through 2013. The aim of material irradiation test system is to conduct IASCC (Irradiation Assisted Stress Corrosion Cracking) evaluation study. This system is mainly consist of water control unit, which can simulate elevated temperature and pressure of the light water reactor environment in the reactor, and load control unit, which can perform the crack propagation examination under irradiation. This load control unit gives a load to CT (Compact Tension) specimen, and perform the crack propagation examination. The principle of loading to CT specimen is using pressure difference between pressure generated by high temperature and high pressure water by water control unit in capsule and pressure generated by load gas pressure supplied by helium gas cylinder in bellows installed in load control unit. In 2013, the commissioning of material irradiation test system was carried out for adjustment. During this commissioning, the correlation between the differential pressure in load control unit and the load was confirmed by using the test container connected to load control unit with load cell. From the results of commissioning, the problem, which the load change speeds at loading and unloading were different due to different pressure change speeds by the piping resistance performance in the periodic loading test in which load from minimum to maximum repeatedly applied, was confirmed. This report summarizes the problem of load change speed due to the piping resistance performance, which was confirmed in 2013, the improvement and performance test of load control unit for solving the problem described above, which were carried out from 2014 to 2015, and operating procedure.
Machida, Masahiko; Yamada, Susumu; Kim, M.; Okumura, Masahiko; Miyamura, Hiroko; Malins, A.; Shikaze, Yoshiaki; Sato, Tomoki*; Numata, Yoshiaki*; Tobita, Yasuhiro*; et al.
RIST News, (68), p.3 - 19, 2022/09
no abstracts in English
Morita, Hisashi; Daigo, Fumihisa; Sayato, Natsuki; Watahiki, Shunsuke; Kojima, Kazuki; Nakayama, Kazuhiko; Ide, Hiroshi
JAEA-Technology 2021-030, 166 Pages, 2022/05
JAEA-Technology-2021-030.pdf:3.65MB
When the roof of the JMTR Hot Laboratory (HL) building was repaired for rain leaks in January, 2015, thinning was found at one of the anchor bolts on base of the HL exhaust stack. Moreover, the thinning of some anchor bolts and gaps between the anchor bolt nuts and flange plate was found in the later investigation for the exhaust stack. Since the possibility of the exhaust stack collapsing cannot be denied, it was removed. Therefore, it became necessary to rebuild a new exhaust stack as soon as possible. The design of the new exhaust stack was based on the measures to prevent rainwater intrusion into the base, which was the cause of the thinning of the anchor bolts found in the investigation, and on the new regulatory standards established after the accident at the Fukushima Daiichi Nuclear Power Station. Furthermore, since the new exhaust stack corresponds to buildings and structures that must undergo building confirmation, the soundness of the new exhaust stack against seismic force and wind load was evaluated based on the Building Standards Law and the Stack Structure Design Guideline. This report described the basic design of the new exhaust stack.
Department of JMTR
JAEA-Review 2021-064, 201 Pages, 2022/03
JAEA-Review-2021-064.pdf:22.0MB
In the "The study committee on Post-JMTR" which aims at discussing for the construction of a new materials testing reactor as Post JMTR, it was proposed to hold a workshop to promote the public understanding and to hear the opinions of utilization needs. In addition, it was proposed that the workshop be held regularly as a place for exchanging opinions about ideal way of the new materials testing reactor, and that discussing be held with no limit to Japan. In response to these proposals, the workshop was held to discuss the construction of the new materials testing reactor. This workshop was held with the aim of clarifying the utilization needs of the new materials testing reactor. In the workshop, it was given lecture on safety improvement of light-water reactors, nuclear research and development of new and next-generation reactors, scientific and academic research of basic research on materials, and industrial applications for RI production by stakeholders in industry and academia. In addition, panel discussions were held to freely discuss the utilization needs required for the new materials testing reactor, the ideal situation of irradiation functions in Japan, and the operation and use of facilities. This proceeding is a compilation of these presentations and others.
