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Journal Articles

Japan Atomic Energy Agency; Contribution to the decommissioning of the Fukushima Daiichi Nuclear Power Station and the reconstruction of Fukushima Prefecture at the Naraha center for Remote Control technology development

Morimoto, Kyoichi; Ono, Takahiro; Kakutani, Satomi; Yoshida, Moeka; Suzuki, Soichiro

Journal of Robotics and Mechatronics, 36(1), p.125 - 133, 2024/02

The Naraha Center for Remote Control Technology Development was established for the purpose of developing and verifying remote control equipment for promoting the decommissioning of the Fukushima Daiichi Nuclear Power Station and the external use of this center was started in 2016. The mission of this center is to contribute to the decommissioning of the Fukushima Daiichi Nuclear Power Station and for the reconstruction of Fukushima Prefecture. In this review, we describe the equipment related to the full-scale mock-up test, the component test for a remote-control device and the virtual reality system in this center. In addition, the case examples for usage of these equipment are introduced.

JAEA Reports

Development of genetic and electrochemical diagnosis and inhibition technologies for invisible corrosion caused by microorganisms (Contract research); FY2022 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; National Institute for Materials Science*

JAEA-Review 2023-031, 101 Pages, 2024/01

JAEA-Review-2023-031.pdf:24.47MB

The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") in FY2022. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station (1F), Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2020, this report summarizes the research results of the "Development of genetic and electrochemical diagnosis and inhibition technologies for invisible corrosion caused by microorganisms" conducted from FY2020 to FY2022. The present study aims to develop innovative diagnostic techniques such as accelerated test specimens and on-site genetic testing for microbially induced and accelerated corrosion of metallic materials (microbially influenced corrosion, MIC), and to identify the conditions that promote MIC at 1F for proposing methods to prevent MIC through water quality and environmental control.

Journal Articles

Behavior of radiocesium ($$^{137}$$Cs) on the coastal seafloor near the Fukushima Daiichi Nuclear Power Plant inferred from radiocesium distributions in long cores

Nakanishi, Takahiro; Tsuruta, Tadahiko; Misono, Toshiharu; Shiribiki, Takehiko; Urabe, Yoshimi*; Sanada, Yukihisa

Journal of Coastal Research, 116(SI), p.161 - 165, 2024/01

Continuous data of Cs-137 concentration in surface seabed sediment around the Fukushima Daiichi Nuclear Power Plant (FDNPP) from 2012 to 2022 was compiled and its temporal change was fitted by exponential function. In general, Cs-137 concentrations were gradually declining with time. However, at some monitoring points in shallow region, long half-lives and/or large deviations of Cs-137 concentrations were noticed. To gain insight into cesium dynamics in shallow seafloor, long sediment cores were collected at shallow region near the FDNPP, and the vertical profiles of Cs-137 concentration and particle size distribution were determined. At the beach, Cs-137 concentration and particle size distribution were very homogenized from several tens of cm to more than 1 m deep, probably due to strong vertical mixing by wind waves and tides. Therefore, beach sediments have significant Cs-137 reserves in deeper layers at present. It was suggested that the Cs-137 supply from deep layers as well as the land area might suppress the decline of surface Cs-137 concentration in this area. At sampling points located at the bases of cliffs and depressions at the offshore zone, the vertical distributions of Cs-137 concentration were highly heterogeneous, showing the particle size dependency. Moreover, Cs-137 profiles obtained at the same point for several years were quite different. Therefore, it might cause the large fluctuation of Cs-137 concentration at surface sediment over time.

Journal Articles

Integration of multiple partial point clouds based on estimated parameters in photogrammetry with QR codes

Baba, Keita*; Watanobe, Yutaka*; Nakamura, Keita*; Matsumoto, Taku; Hanari, Toshihide; Kawabata, Kuniaki

Proceedings of 29th International Symposium on Artificial Life and Robotics (AROB 2024) (Internet), p.751 - 756, 2024/01

Journal Articles

Preliminary study of the criticality monitoring method based on the simulation for the activity ratio of short half-life noble-gas fission products from fuel debris

Riyana, E. S.; Okumura, Keisuke; Sakamoto, Masahiro; Matsumura, Taichi; Terashima, Kenichi; Kanno, Ikuo

Journal of Nuclear Science and Technology, 8 Pages, 2024/00

Journal Articles

Development of a radiation tolerant laser-induced breakdown spectroscopy system using a single crystal micro-chip laser for remote elemental analysis

Tamura, Koji; Nakanishi, Ryuzo; Oba, Hironori; Karino, Takahiro; Shibata, Takuya; Taira, Takunori*; Wakaida, Ikuo

Journal of Nuclear Science and Technology, 8 Pages, 2024/00

Journal Articles

$$^{137}$$Cs contamination of Japanese mustard spinach by resuspended particles in areas with different contamination conditions

Tatsuno, Takahiro*; Yoshimura, Kazuya; Nihei, Naoto*

Journal of Radioanalytical and Nuclear Chemistry, 8 Pages, 2024/00

JAEA Reports

Annual report of Nuclear Emergency Assistance and Training Center (April 1, 2022 - March 31, 2023)

Nuclear Emergency Assistance and Training Center

JAEA-Review 2023-026, 54 Pages, 2023/12

JAEA-Review-2023-026.pdf:3.26MB

The Japan Atomic Energy Agency (JAEA) is one of the designated public corporations, which is the agency dealing with emergency situations in cooperation with the Japanese and local governments under the Disaster Countermeasures Basic Act and under the Armed Attack Situation Response Law. JAEA has, therefore, responsibilities of providing technical assistances to the Japanese and local governments in case of nuclear or radiological emergencies based on these acts. To fulfill the assistances, the JAEA has prepared the Nuclear Emergency Support Measures Regulation, Disaster Prevention Work Plan and Civil Protection Work Plan. The Nuclear Emergency Assistance and Training Center (NEAT) is the main center of the technical assistance in case of emergency, and dispatches experts of JAEA, supplies equipment and materials and gives technical advice and information, to the Japanese and local governments for emergency based on the regulation and plans. In normal time, the NEAT provides the technical assistances such as the exercises and training courses concerning the nuclear preparedness and response to the JAEA experts and to emergency responders including the Japanese and local government officers. This report introduces the results of activities in Japanese Fiscal Year 2022, conducted by the NEAT.

JAEA Reports

Development of rapid and sensitive radionuclide analysis method by simultaneous analysis of $$beta$$, $$gamma$$, and X-rays (Contract research); FY2022 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Japan Chemical Analysis Center*

JAEA-Review 2023-022, 93 Pages, 2023/12

JAEA-Review-2023-022.pdf:4.7MB

The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") in FY2022. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2020, this report summarizes the research results of the "Development of rapid and sensitive radionuclide analysis method by simultaneous analysis of $$beta$$, $$gamma$$, and X-rays" conducted from FY2020 to FY2022. The present study aims to enable rapid analysis of radionuclides in fuel debris and waste, we have established the latest measurement system, such as the multiple $$gamma$$-ray detection methods, and the Spectral Determination Method (hereinafter referred to as "SDM") was developed. In the research in 2022, we developed a code that handles measurement data of LSC, singles Ge, and 2D spectra (multiple $$gamma$$). In addition, to develop an integrated database, spectral data of 40 nuclides were obtained by actual measurements and simulation calculations.

JAEA Reports

Technology development of diamond-base neutron sensors and radiation-resistive integrated-circuits for shielding-free criticality approach monitoring system (Contract research); FY2022 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; High Energy Accelerator Research Organization*

JAEA-Review 2023-020, 90 Pages, 2023/12

JAEA-Review-2023-020.pdf:6.59MB

The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") in FY2022. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2020, this report summarizes the research results of the "Technology development of diamond-base neutron sensors and radiation-resistive integrated-circuits for shielding-free criticality approach monitoring system" conducted from FY2020 to FY2022. The present study aims to develop key components of neutron detection system without a radiation shield for a criticality approach monitoring system with high neutron detection efficiency (a few count/nv) under high gamma ray background (1kGy/h). Developed components are neutron detection devices based on diamond sensors and a high radiation resistive signal-processing data-transfer system based on radiation resistive integrated circuit technologies.

JAEA Reports

Analysis of deposits inside the reactor at Fukushima Daiichi Nuclear Power Station in JFY2021; The Subsidy program of "Project of Decommissioning and Contaminated Water Management (Development of Analysis and Estimation Technology for Characterization of Fuel Debris)" starting FY2021

Ikeuchi, Hirotomo; Sasaki, Shinji; Onishi, Takashi; Nakayoshi, Akira; Arai, Yoichi; Sato, Takumi; Ohgi, Hiroshi; Sekio, Yoshihiro; Yamaguchi, Yukako; Morishita, Kazuki; et al.

JAEA-Data/Code 2023-005, 418 Pages, 2023/12

JAEA-Data-Code-2023-005-01.pdf:24.59MB
JAEA-Data-Code-2023-005-02.pdf:32.18MB

For safe and steady decommissioning of Tokyo Electric Power Company Holdings' Fukushima Daiichi Nuclear Power Station (1F), information concerning composition and physical/chemical properties of fuel debris generated in the reactors should be estimated and provided to other projects conducting the decommissioning work including the retrieval of fuel debris and the subsequent storage. For this purpose, in FY2021, samples of contaminants (the wiped smear samples and the deposits) obtained through the internal investigation of the 1F Unit 2 were analyzed to clarify the components and to characterize the micro-particles containing uranium originated from fuel (U-bearing particles) in detail. This report summarized the results of analyses performed in FY2021, including the microscopic analysis by SEM and TEM, radiation analysis, and elemental analysis by ICP-MS, as a database for evaluating the main features of each sample and the probable formation mechanism of the U-bearing particles.

Journal Articles

Arrangements for telephone consultation on radiation health effects in a nuclear emergency in Japan; Lessons learned from the nuclear accident in Fukushima, Japan, 2011

Okuno, Hiroshi; Kawakami, Takeshi; Watanabe, Fumitaka; Horikoshi, Hidehiko*

Journal of Disaster Research, 18(8), p.911 - 917, 2023/12

In response to residents' concerns about the radiation health effects following the nuclear accidents at the Fukushima Daiichi Nuclear Power Station of the Tokyo Electric Power Company in March 2011, the Japan Atomic Energy Agency (JAEA) established a telephone consultation system. Eight toll-free telephone lines were prepared, and employees with knowledge of radiation health effects were assigned for consultation. Approximately 35,000 consultations were conducted from March 17, 2011, to September 18, 2012. The results of the text mining analysis revealed that the greatest source of anxiety was the impact on children's health from radiation. The JAEA's system for telephone consultation was improved following this telephone consultation experience. The description of telephone hotlines in the International Atomic Energy Agency (IAEA) guide, GSG-14, was discussed for further improvements of the JAEA's telephone consultation system.

Journal Articles

Effect of fuel particle size on consequences of criticality accidents in water-moderated solid fuel particle dispersion system

Fukuda, Kodai; Yamane, Yuichi

Journal of Nuclear Science and Technology, 60(12), p.1514 - 1525, 2023/12

This study aims to clarify the effect of fuel particle radius on the criticality transient behavior and the total number of fissions in water-moderated solid fuel dispersion systems. Neutronics/thermal hydraulics-coupled kinetics analysis was performed in a hypothetical fuel debris system, where small fuel particles aggregate in water and become supercritical. Results showed that the number of fissions is 10 times larger when the fuel particle radius is reduced by one order of magnitude under conditions where heat transfer, i.e. from fuel to water, is emphasized. Moreover, there is a possibility that lower reactivity could give a larger number of fissions when the fuel particle size is very small. In addition, the number of fissions may be overestimated or underestimated to an unexpected extent unless appropriate fuel particle size is set on the analysis.

Journal Articles

Application of USV to marine monitoring after Fukushima Daiichi Nuclear Power Plant Accident and its applicability as a nuclear disaster prevention tool

Sanada, Yukihisa; Misono, Toshiharu; Shiribiki, Takehiko*

Kaiyo Riko Gakkai-Shi, 27(2), p.37 - 44, 2023/12

This paper summarizes the general situation of marine monitoring conducted after the Fukushima Daiichi Nuclear Power Plant accident, the experience of development and operation of USVs, and the possibility of applying unmanned vessels as a tool for nuclear disaster prevention in the future. 0.01 Bq/L or less for seawater and 10 Bq/L or less for seabed soil. Operational tests of three USVs have been continuously conducted for use in such environmental radiation monitoring. Development of these UAVs is underway with a view to utilizing them for seawater sampling, direct measurement of the seafloor soil surface layer, and seafloor soil sampling, depending on their performance. It is necessary to promote the development of USVs for future nuclear power plant accidents.

Journal Articles

MAAP code analysis focusing on the fuel debris conditions in the lower head of the pressure vessel in Fukushima-Daiichi Nuclear Power Station Unit 3

Sato, Ikken; Yoshikawa, Shinji; Yamashita, Takuya; Shimomura, Kenta; Cibula, M.*; Mizokami, Shinya*

Nuclear Engineering and Design, 414, p.112574_1 - 112574_20, 2023/12

Journal Articles

Development of a large-area alpha imaging detector for hand and foot monitors

Morishita, Yuki; Higuchi, Mikio*; Kaneko, Junichi*; Kitagawa, Yuichi*; Akedo, Jun*; Soma, Mitsugu*; Matsui, Hiroaki*

Nuclear Instruments and Methods in Physics Research A, 1057, p.168702_1 - 168702_8, 2023/12

This paper describes the development of a large-area imaging detector capable of measuring the detailed distribution of alpha particles on hands and feet for use in entry/exit control monitors in decommissioning sites such as the Fukushima Daiichi Nuclear Power Plant. The detector was developed using a commercially available ZnS(Ag) scintillator and an electron multiplying CCD camera. The effectiveness of the detector was evaluated by measuring several types of radiation sources, and the results showed that it was possible to detect the position of alpha particles in a very short time, and contamination levels of up to 11 Bq/cm$$^{2}$$ could be visualized. As a result of the minimal detectable surface activity concentration evaluations, 2.0 minutes or more is required to achieve 4 Bq/cm$$^{2}$$, and 25.0 minutes or more is required to achieve 0.4 Bq/cm$$^{2}$$. The field of view of the detector was also checked, and it was confirmed that the setup had a field of view that could cover most of the hand and the sole of the shoe. This detector is expected to be useful for preventing internal uptake and decontamination.

Journal Articles

Effect of molybdenum release on UO$$_{2}$$/MOX fuel oxidation under severe light water reactor accident conditions

Liu, J.; Miwa, Shuhei; Karasawa, Hidetoshi; Osaka, Masahiko

Nuclear Materials and Energy (Internet), 37, p.101532_1 - 101532_5, 2023/12

Journal Articles

Automatic system for sequential reconstruction from image sequences acquired from a camera by SfM-MVS

Matsumoto, Taku; Hanari, Toshihide; Kawabata, Kuniaki; Yashiro, Hiroshi*; Nakamura, Keita*

Proceedings of 2023 IEEE International Conference on Robotics and Biomimetics (IEEE ROBIO 2023) (Internet), 7 Pages, 2023/12

JAEA Reports

Effect of preparation conditions and storage time on characteristic and rheological properties of carbonate slurries

Kato, Tomoaki; Yamagishi, Isao

JAEA-Technology 2023-018, 53 Pages, 2023/11

JAEA-Technology-2023-018.pdf:2.6MB

In the decommissioning of Fukushima Daiichi Nuclear Power Station, radioactive carbonate slurry waste was generated using the Advanced Liquid Processing System (ALPS) pretreatment and temporarily stored in a high integrity container (HIC). In 2015, overflow of supernatant from HIC estimate as bubble retention in the carbonate slurry was discovered, increasing the need for a safety assessment of the carbonate slurry stored the HIC (HIC slurry). In this study, a carbonate slurry (simulated slurry) was prepared according to the Mg/Ca mass ratio in the ALPS inlet water of the HIC slurry which overflew the HIC. The effects of reaction time during the pretreatment process, suspended solids concentration (SS concentration), and settling time on the particle composition, morphology and rheological properties of the slurry were investigated. Evaluating the effect of reaction time and concentration process on chemical properties in slurry production, the effect of the reaction time was not confirmed in the simulated slurry that had undergone the concentration process, and slurry prepared at SS concentration of 150 g/L was composed of formless particles have a particle diameter of 0.4 $$mu$$m or less. We also investigate the effect of SS concentration on sedimentability, decrease in SS concentration by dilution with processing solution contributed to an increase in the initial slurry settling velocity. Furthermore, two different flow characteristics were observed depending on the settling time, suggesting that the slurry at the initial settling time has non-Bingham flow properties, whereas it changes to Bingham flow properties as the settling time becomes longer. In addition, yield stress was increased with settling time, and this yield stress was found to be exponentially proportional to the density of the slurry. These results provide knowledge to estimate the current state of HIC slurry and are expected to contribute to the safety assessment.

5830 (Records 1-20 displayed on this page)