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JAEA Reports

Countermeasure against Beyond Design Basis Accident of HTTR by using fire engine

Shimazaki, Yosuke; Jidaisho, Tatsuya; Ishii, Toshiaki; Inoi, Hiroyuki; Iigaki, Kazuhiko

JAEA-Technology 2024-005, 23 Pages, 2024/06

JAEA-Technology-2024-005.pdf:5.53MB

HTTR has newly assumed Beyond Design Basis Accident (BDBA) as part of conformity assessment with the new regulatory standards and has established measures to prevent the spread of BDBA. Among these measures, to prevent the spread of BDBA caused by cooling water leaks from spent fuel storage pool, the Oarai Research Institute's fire engine was selected as an equipment to prevent the spread of BDBA, and required performances such as pumping water performance were determined. After all required performances were confirmed by inspections, the fire engine passed the operator's pre-use inspection and contributed to the restart of the HTTR operations.

JAEA Reports

Differential pressure rise event for filters of HTTR primary helium gas circulators, 2; Investigation of filter deposits and recurrence prevention measures

Nemoto, Takahiro; Fujiwara, Yusuke; Arakawa, Ryoki; Choyama, Yuya; Nagasumi, Satoru; Hasegawa, Toshinari; Yokoyama, Keisuke; Watanabe, Masashi; Onishi, Takashi; Kawamoto, Taiki; et al.

JAEA-Technology 2024-003, 17 Pages, 2024/06

JAEA-Technology-2024-003.pdf:1.91MB

In order to investigate the cause of the increase in differential pressure in the primary helium circulator filter that occurred during the RS-14 cycle, a clogged filter was investigated. As a result of the investigation, deposits caused by silicone oil were confirmed on the surface of the filter element. These results revealed that the cause of filter clogging was silicone oil mixed into the primary system due to performance deterioration of the charcoal filter in the gas circulator of primary helium purification system. As a measure to prevent the recurrence of this event, in addition to the conventional management based on operating hours for replacing of charcoal filter in the gas circulator of primary helium purification system, we have established a new replacement plan for every three years.

JAEA Reports

Proposal of simple model for investigating irradiation behavior of nuclear-grade graphite

Saijo, Tomoaki; Mizuta, Naoki; Hasegawa, Toshinari; Suganuma, Takuro; Shimazaki, Yosuke; Ishihara, Masahiro; Iigaki, Kazuhiko

JAEA-Technology 2024-002, 96 Pages, 2024/06

JAEA-Technology-2024-002.pdf:22.18MB

Nuclear-grade graphite is used for core components of High Temperature Engineering Test Reactor (HTTR) due to excellent heat resistant properties. The physical properties of this graphite change with temperature and neutron irradiation, as well as exhibit complex behavior such as irradiation deformation and creep deformation. Then, stress analysis code has been developed for the graphite. In previous study, the code has been used to evaluate the shutdown stress by residual strain that accumulates with neutron irradiation. However, the effects of change in physical properties such as Young's modulus and thermal expansion-coefficient on shutdown stress have not been fully understood. Therefore, an evaluation model based on a simplified beam model was developed to clarify the effects of changes in physical properties and complex deformations on stresses occurring during operation and reactor shutdown, and to contribute to the development of graphite structures with longer lifetimes. As an application example, the effects of changes on various physical properties on operational and shutdown stresses were clarified for graphite components in the temperature range from 600 to 800$$^{circ}$$C.

JAEA Reports

Establishment of characterization method for small fuel debris using the world's first isotope micro imaging apparatus (Contract Research); FY2021 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Kogakuin University*

JAEA-Review 2024-005, 79 Pages, 2024/06

JAEA-Review-2024-005.pdf:5.72MB

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 FY2021. 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 FY2021, this report summarizes the research results of the "Establishment of characterization method for small fuel debris using the world's first isotope micro imaging apparatus" conducted in FY2021. The present study aims to obtain, for the first time in the world, the important data necessary for clarifying the retrieval of small amounts of fuel debris, and to evaluate and examine them. SEM-EDS and TEM-EDS cannot be used for isotopic identification and analysis of Pu and B. On the other hand, bulk analysis such as ICP-MS lacks the information in a micro region.

JAEA Reports

Uniaxial compression tests on siliceous mudstone of the Wakkanai Formation under high temperature conditions

Mochizuki, Akihito; Sato, Toshinori; Wada, Junichi*

JAEA-Research 2024-003, 86 Pages, 2024/06

JAEA-Research-2024-003.pdf:8.13MB

For the geological disposal of high-level radioactive waste, research and studies are being conducted in Japan and abroad to contribute to the mitigation of the upper temperature limit (100$$^{circ}$$C) in the buffer material assumed in the current disposal system. In this study, uniaxial compression tests under several temperature conditions, some of which exceed 100$$^{circ}$$C, were conducted to understand changes in rock properties under high temperature conditions, using siliceous mudstone (Wakkanai formation) from Horonobe, Hokkaido, as a case study. The uniaxial compressive strength of the rock increased with heating temperature. The uniaxial compressive strength of specimens heated above 100$$^{circ}$$C was comparable to that of specimens desiccated before testing. Mineralogical observations by scanning electron microscopy showed no evidence of alteration of pore structure or minerals, as observed in other rocks in previous studies. In conclusion, the increase in strength of siliceous mudstone with heating temperature observed in this study is considered to be due to the drying of the specimens with heating.

JAEA Reports

Stabilization treatment of the sludge items containing nuclear materials at Plutonium Conversion Development Facility

Tanigawa, Masafumi; Nakamura, Daishi; Asakawa, Naoya*; Seya, Kazuhito*; Omori, Fumio*; Koiso, Katsuya*; Horigome, Kazushi; Shimizu, Yasuyuki

JAEA-Technology 2024-001, 37 Pages, 2024/05

JAEA-Technology-2024-001.pdf:2.32MB

At plutonium conversion development facility, the neutralization sedimentation and the coagulation sedimentation (sludge) items are stored in a polyethylene container packed in the plastic bag. The neutralization sedimentation items and the coagulation sedimentation items are stored in the globe box and storage room in the facility, respectively. Some sludge items generate gases, that swelled the plastic bag. We should ensure whether the bag swelling by visual confirmation. When the swelling is confirmed, those containers are transferred to the glove box to exchange the plastic bag for new one. By keeping the above procedure, those items were stored safely in the facility since its founding. The stabilization work for enhance the safe storage was planned to reduce the gas generation of the sludge items caused by the radiolysis of water. Those sludge items have the containing a sodium nitrate that has moisture-absorption characteristic. Therefore, the stabilization method aimed to remove the sodium nitrate from the items. The work was conducted from August 2018 to August 2022. The sodium concentration in items were reduced to 3 wt% or lower. Each stabilized sludge item packed in plastic bag were confirmed its swelling for over one year in the storage place. No gas generation from all item has been observed for more than the one year. And while both the neutralization and the coagulation sedimentation items were stored they were not the increasing of the moisture in the items. As a result, those items were evaluated that will not generate gases any more and confirmed to be stabilized after this treatment. Then, those neutralization sedimentation items were stored in powder cans and transferred to powder storage room as a retained waste. Based on the above results, risks of the gas generation from sludge items were decreased enough. Therefore, the safety of the stored sludge item was improved and confirmed.

JAEA Reports

Report of nuclear data roadmap 2023

Nakayama, Shinsuke

JAEA-Review 2024-009, 16 Pages, 2024/05

JAEA-Review-2024-009.pdf:1.17MB

Nuclear data is fundamental data for nuclear energy research and development, and its importance has been widely recognized. On the other hand, for future nuclear data research, it is necessary to sort out which types of data (target nuclides, energies, physical quantities, etc.) should be prioritized. Therefore, a "Task Force (TF) for Nuclear Data Roadmap" was established within Investigation Committee on Nuclear Data in the Atomic Energy Society of Japan to discuss a roadmap for future nuclear data research and development. This document reports the results of the discussion in the TF.

JAEA Reports

Annual report of Engineering Services Department on JFY2022

Engineering Services Department

JAEA-Review 2024-001, 78 Pages, 2024/05

JAEA-Review-2024-001.pdf:4.08MB

The Engineering Services Department is in charge of operation and maintenance of utility facilities (water distribution systems, electricity supply systems, steam generation systems and drain water systems etc.) in whole of the institute. And also is in charge of operation and maintenance of specific systems (power receiving and transforming facilities, an emergency electric power supply system, an air/liquid waste treatment system, a compressed air supply system) in nuclear reactor facilities, nuclear fuel material usage facilities and usual facilities or buildings. In addition, the department is in charge of maintenance of buildings, design and repair of electrical/mechanical equipment. This annual report describes summary of activities, operation and maintenance data and technical developments of the department carried out in JFY 2022.We hope that this report may help to future work.

JAEA Reports

Development of environmental mitigation technology with novel water purification agents (Contract research); FY2022 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Shinshu University*

JAEA-Review 2023-053, 87 Pages, 2024/05

JAEA-Review-2023-053.pdf:4.67MB

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 environmental mitigation technology with novel water purification agents" conducted from FY2020 to FY2022. The present study aims to develop a reusable adsorbent for strontium ions with high adsorption property to contribute to the improvement of the treatment process of radioactive contaminated water generated by the Great East Japan Earthquake. As a result, reusable adsorbent materials showing excellent Sr adsorption performances were developed. The current adsorbent materials for strontium are extremely expensive and single use, so the storage and disposal of massive generation of waste have become a major problem.

JAEA Reports

Development of a hybrid method for evaluating the long-term structural soundness of nuclear reactor buildings using response monitoring and damage imaging technologies (Contract research); FY2022 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Tohoku University*

JAEA-Review 2023-048, 151 Pages, 2024/05

JAEA-Review-2023-048.pdf:8.48MB

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 FY2021, this report summarizes the research results of the "Development of a hybrid method for evaluating the long-term structural soundness of nuclear reactor buildings using response monitoring and damage imaging technologies" conducted in FY2022. The present study aims to develop an evaluation method necessary to obtain a perspective on the long term structural soundness of accident-damaged reactor buildings, where accessibility to work sites is extremely limited due to high radiation dose rate and high contamination. In FY2022, the second year of the three-year plan, some tests and other activities on the following research items were conducted following FY2021, based on the specific research methods and research directions clarified in FY2021.

JAEA Reports

Improvement of aerosol time-of-flight mass spectrometer for on-line measurement of tiny particles containing alpha emitters (Contract research); FY2022 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Osaka University*

JAEA-Review 2023-040, 104 Pages, 2024/05

JAEA-Review-2023-040.pdf:5.01MB

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 FY2021, this report summarizes the research results of the "Improvement of aerosol time-of-flight mass spectrometer for on-line measurement of tiny particles containing alpha emitters" conducted in FY2022. The present study aims to improve Aerosol Time-Of-Flight Mass Spectrometer (ATOFMS) in order to monitor tiny particles containing alpha emitters such as U and Pu generated in removing debris from the reactors of 1F. In FY2022, we newly fabricated a prototype of the improved ATOFMS and measured collection and detection efficiencies of the particle detection unit and carried out mass measurement using the TOF part.

JAEA Reports

Challenge to advancement of debris composition and direct isotope measurement by microwave-enhanced LIBS (Contract research); FY2022 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; i-Lab*

JAEA-Review 2023-029, 77 Pages, 2024/05

JAEA-Review-2023-029.pdf:3.98MB

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 "Challenge to advancement of debris composition and direct isotope measurement by microwave-enhanced LIBS" conducted from FY2020 to FY2022. The present study aims to increase the emission intensity of LIBS (laser-induced breakdown spectroscopy) by superimposing MW (microwave) and apply it to uranium isotope measurement. In FY2022, we improved the cooling method and reduce unnecessary functions in of the semiconductor microwave oscillator, and apply the optimized conditions obtained from simulations to the LIBS experiment for the microwave antenna gave better results.

JAEA Reports

Analysis of the relationship between operational quantity used for area monitoring and protection quantity for external exposure

Endo, Akira

JAEA-Research 2024-002, 90 Pages, 2024/05

JAEA-Research-2024-002.pdf:4.22MB

This report presents a comprehensive analysis of the relationship between three quantities used for area monitoring - ambient dose equivalent $$H^*(10)$$, maximum dose equivalent $$H^*_textrm{max}$$, and ambient dose $$H^*$$ - and effective dose for external irradiation by photons, neutrons, electrons, positrons, protons, muons, pions, and helium ions. For the analysis, calculations were performed using PHITS (Particle and Heavy Ion Transport code System) and the ICRU sphere. The analysis result shows that $$H^*(10)$$ and $$H^*_textrm{max}$$ can induce large differences in the estimation of effective dose over a wide energy range for various particle types covered by ICRP Publication 116 while $$H^*$$ can conservatively estimate effective dose within the acceptable range for area monitoring. In other words, $$H^*(10)$$ and $$H^*_textrm{max}$$ have limitations in estimating effective dose, and using $$H^*$$ is recommended as a more appropriate quantity for the purpose. This conclusion supports the proposal of ICRU Report 95 to use $$H^*$$ for estimating effective dose in various external exposure situations. The use of ambient dose $$H^*$$ is particularly important in situations where various types of radiation are encountered, such as the use of radiation in the medical and academic fields and exposure in aviation and can meet the evolving requirements of radiation monitoring for the expansion of the field of radiological protection.

JAEA Reports

Study of the applicability of SrI$$_{2}$$(Eu) scintillation detector to in-situ gamma-ray spectrometry

Takeyasu, Masanori; Mikami, Satoshi; Ando, Masaki; Hokama, Tomonori

JAEA-Testing 2023-005, 17 Pages, 2024/03

JAEA-Testing-2023-005.pdf:1.16MB

As part of the research aimed at developing a detector to easily perform in-situ gamma-ray spectrometry, the applicability of a SrI$$_{2}$$(Eu) scintillation detector to in-situ gamma-ray spectrometry was investigated. In this study, the characteristics of the SrI$$_{2}$$(Eu) detector were evaluated for in-situ gamma-ray spectrometry. Intercomparison measurements of in-situ gamma-ray spectrometry using the SrI$$_{2}$$(Eu) detector and Ge semiconductor detectors were conducted, and the applicability of the SrI$$_{2}$$(Eu) detector was examined. To characterize the SrI$$_{2}$$(Eu) detector, the peak efficiency of the SrI$$_{2}$$(Eu) detector was measured with respect to the change of incident gamma-ray energy. The angular dependence of the peak efficiency of the SrI$$_{2}$$(Eu) detector was also measured. As the result of the intercomparison measurement of in-situ gamma-ray spectrometry, the radionuclides quantified by Ge detectors were Cs-134, Cs-137, Pb-214, Bi-214, Tl-208, Ac-228 and K-40. On the other hand, those by SrI$$_{2}$$(Eu) detector were only Cs-137 and K-40 which had relatively high radioactive intensity. The deposition density of Cs-137 and the concentration of K-40 in soil measured by the SrI$$_{2}$$(Eu) detector showed relatively good agreements with those by Ge detectors. From these results, it was suggested that the in-situ measurement using a SrI$$_{2}$$(Eu) detector was available for radionuclides which had high radioactive intensity and whose gamma-ray peaks were not interfered by those of other radionuclides in gamma-ray spectrum. During an accident at nuclear power plant, various radionuclides are released into the environment, but radionuclides with short half-life decayed and radionuclides with long half-life only exist at mid-to-long term environmental monitoring situations, when in-situ gamma-ray spectrometry using a SrI$$_{2}$$(Eu) detector is applicable.

JAEA Reports

FBR metallic materials test manual (2023 revised edition)

Imagawa, Yuya; Toyota, Kodai; Onizawa, Takashi; Kato, Shoichi

JAEA-Testing 2023-004, 76 Pages, 2024/03

JAEA-Testing-2023-004.pdf:2.08MB

This manual describes the methods for conducting material tests in air, argon gas, and sodium, and for organizing the data obtained, as a part of the development of high-temperature structural design technology for fast reactors. This manual reflects the revision of test methods in Japanese Industrial Standards (JIS) to the "FBR Metallic Materials Test Manual, PNC TN241 77-03" published in 1977 and the "FBR Metallic Materials Test Manual (Revised Edition), JNC TN9520 2001-001" published in 2001. Also, it was written with reference to the recommended room temperature / elevated temperature tensile test method by the Japan Society of Mechanical Engineers (JSME) and the test standard for the elevated-temperature low-cycle fatigue test method by the Society of Materials Science, Japan (JSMS), which are the standard for material test methods in the domestic academic society.

JAEA Reports

Assessment of probability of aircraft crashes for Nuclear Science Research Institute

Kamikawa, Yutaka; Suzuki, Makoto; Agake, Toshiki; Murakami, Takahiko; Morita, Yusuke; Shiina, Hidenori; Fukushima, Manabu; Hirane, Nobuhiko; Ouchi, Yasuhiro

JAEA-Technology 2023-030, 57 Pages, 2024/03

JAEA-Technology-2023-030.pdf:1.93MB

Owing to the publication of the latest data about aircraft crashes by Nuclear Regulation Authority (NRA), it was necessary to re-evaluate the probabilities of aircraft crashes for Nuclear Science Research Institute (NSRI). By using of the assessment method provided in "Regulatory Guide of the Assessment Standard for Probability of Airplane Crash on a Nuclear Power Reactor Facility", we re-evaluated the probabilities of aircraft crashes against the nuclear facilities in NSRI. As a result of the evaluations, the sum of the probabilities of aircraft crashes against Waste Treatment Facilities (maximum probability among all nuclear facilities in NSRI) is 5.68$$times$$10$$^{-8}$$ (times/(reactor $$cdot$$ year)) which is lower than 10$$^{-7}$$ (times/(reactor $$cdot$$ year)) that is the assessment criterion whether aircraft crashes is considered to be "anticipated external human induced events" in design basis or not.

JAEA Reports

Utilization of gamma ray irradiation at the WASTEF Facility

Sano, Naruto; Yamashita, Naoki; Watanabe, Masaya; Tsukada, Manabu*; Hoshino, Kazutoyo*; Hirai, Koki; Ikegami, Yuta*; Tashiro, Shinsuke; Yoshida, Ryoichiro; Hatakeyama, Yuichi; et al.

JAEA-Technology 2023-029, 36 Pages, 2024/03

JAEA-Technology-2023-029.pdf:2.47MB

At the Waste Safety Testing Facility (WASTEF), the gamma ray irradiation device "Gamma Cell 220" was relocated from the 4th Research Building of the Nuclear Science Research Institute in FY2019, and the use of gamma ray irradiation has begun. Initially, Fuel Cycle Safety Research Group, Fuel Cycle Safety Research Division, Nuclear Safety Research Center, Sector of Nuclear Safety Research and Emergency Preparedness, the owner of this device, conducted the tests as the main user, but since 2022, other users, including those outside the organization, have started using it. The gamma ray irradiation device "Gamma Cell 220" is manufactured by Nordion International Inc. in Canada. Since it was purchased in 1989, the built-in $$^{60}$$Co radiation source has been updated once, and safety research related to nuclear fuel cycles, etc. It is still used for this purpose to this day. This report summarizes the equipment overview of the gamma ray irradiation device "Gamma Cell 220", its permits and licenses at WASTEF, usage status, maintenance and inspection, and future prospects.

JAEA Reports

Development of an electrochemical measurement method for carbon steels in radiation source dissolved solution and a corroded specimen analysis method using an imaging plate

Yamashita, Naoki; Aoyama, Takahito; Kato, Chiaki; Sano, Naruto; Tagami, Susumu

JAEA-Technology 2023-028, 22 Pages, 2024/03

JAEA-Technology-2023-028.pdf:1.9MB

At the Fukushima Daiichi Nuclear Power Station (1F), which is currently undergoing decommissioning, there is growing interest in the effects of radiation-emitting radionuclides such as $$^{90}$$Sr and $$^{137}$$Cs on the structural integrity. In particular, the corrosion behavior of carbon steel, which is used in many parts of 1F, is known to change depending on metal cations in solution, but the effects of $$^{90}$$Sr and $$^{137}$$Cs on corrosion are not yet understood. In addition, it is important to investigate the distribution of $$^{90}$$Sr and $$^{137}$$Cs in the rust layer in order to understand the corrosion behavior, but the method has not yet been established. In this study, a glove box was prepared to conduct corrosion tests of carbon steel in NaCl containing $$^{90}$$Sr and $$^{137}$$Cs in the glove box. In addition, in order to clarify the influence of $$^{90}$$Sr and $$^{137}$$Cs, which exist as metal cations in the solution, on the corrosion behavior of carbon steel, we attempted to establish a detection method for radioactive materials in the rust layer using an imaging plate.

JAEA Reports

Radiation monitoring via manned helicopter around the nuclear power station in the fiscal year 2022 (Contract research)

Futemma, Akira; Sanada, Yukihisa; Nagakubo, Azusa; Kawasaki, Yoshiharu*; Iwai, Takeyuki*; Hiraga, Shogo*; Haginoya, Masashi*; Matsunaga, Yuki*; Akutsu, Yuichiro*; Arai, Yoshinori*; et al.

JAEA-Technology 2023-027, 146 Pages, 2024/03

JAEA-Technology-2023-027.pdf:18.12MB

By the accident at Tokyo Electric Power Company's (TEPCO's) Fukushima Daiichi Nuclear Power Station (FDNPS), caused by tsunami triggered by the 2011 off the Pacific coast of Tohoku Earthquake, a large amount of radioactive material was released into the surrounding environment. After the accident, Airborne Radiation Monitoring (ARM) via manned helicopter has been applied as a method to quickly and extensively measure the distribution of radiation. Japan Atomic Energy Agency (JAEA) has continuously conducted ARM via manned helicopter around FDNPS. In this report, we summarize the results of the ARM around FDNPS in the fiscal year 2022, evaluate the changes of ambient dose rates and other parameters based on the comparison to the past ARM results, and discuss the causes of such changes. In order to contribute to improve the accuracy of ambient dose rate conversion, we analyzed the ARM data taking into account undulating topography, and evaluated the effect of this method. Furthermore, the effect of radon progenies in the air on the ARM was evaluated by applying the discrimination method to the measurement results.

JAEA Reports

Background radiation monitoring via manned helicopter and development of technology for radiation monitoring via unmanned airplane for application of nuclear emergency response technique in the fiscal year 2022 (Contract research)

Futemma, Akira; Sanada, Yukihisa; Sasaki, Miyuki; Kawasaki, Yoshiharu*; Iwai, Takeyuki*; Hiraga, Shogo*; Haginoya, Masashi*; Matsunaga, Yuki*; Akutsu, Yuichiro*; Arai, Yoshinori*; et al.

JAEA-Technology 2023-026, 161 Pages, 2024/03

JAEA-Technology-2023-026.pdf:14.66MB

By the accident at Tokyo Electric Power Company's (TEPCO's) Fukushima Daiichi Nuclear Power Station (FDNPS), caused by tsunami triggered by the 2011 off the Pacific coast of Tohoku Earthquake, a large amount of radioactive material was released into the surrounding environment. After the accident, Airborne Radiation Monitoring (ARM) via manned helicopter has been utilized as a method to quickly and extensively measure radiation distribution surrounding FDNPS. In order to utilize ARM and to promptly provide the results during a nuclear emergency, information on background radiation levels, topographical features, and controlled airspace surrounding nationwide nuclear facilities have been prepared in advance. In the fiscal year 2022, we conducted ARM around the Mihama Nuclear Power Station of Kansai Electric Power Company (KEPCO), the Tsuruga Power Station of Japan Atomic Power Company (JAPC), and the Ikata Power Station of Shikoku Electric Power Company (YONDEN), and prepared information on background radiation doses and controlled airspace. In addition, we have developed an aerial radiation detection system via unmanned airplane, which is expected to be an alternative to ARM, during a nuclear emergency. This report summarizes the results and technical issues identified.

23002 (Records 1-20 displayed on this page)