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JAEA Reports

Survey on research and development status of Japanese small modular reactors in OECD/NEA activities (2022-2023)

Takeda, Takeshi; Shibata, Taiju

JAEA-Review 2024-040, 29 Pages, 2024/09

JAEA-Review-2024-040.pdf:1.33MB

An important theme of Japan's 6th strategic energy plan is to indicate the energy policy path towards carbon neutrality by 2050. Policy responses for Japan's nuclear energy research and development (R&D) towards 2030 contain the demonstrations of technologies for small modular reactors (SMRs) through international cooperation by 2030. In light of this energy plan, basic policy initiatives over the next 10 years have been compiled to realize Green Transformation (GX), which simultaneously achieves decarbonization and economic growth. Looking overseas, activities of SMR R&D are active internationally, mainly in the US, Canada, Europe, China, and Russia. These activities are not only by heavy industry manufactures and R&D institutes, but also by venture companies. Under these circumstances, the NEA CSNI has gathered an Expert Group on SMRs (EGSMR) to help estimate the safety effects of SMRs. The EGSMR efforts required the submission of responses to several questionnaires whose main purpose was to collect the latest information on the efforts of SMR deployment and research. The first author of this report responded to this based on information from Hitachi-GE Nuclear Energy, Ltd. and Mitsubishi Heavy Industries, Ltd. as well as JAEA. Most of the responses from Japan to the questionnaires are the information that serves as the basis of CSNI Technical Opinion Paper No. 21 (TOP-21). In this report, the Japan's publicly available responses to the questionnaires arranged and additional information are explained, which complements some of the content of the TOP-21. In this manner, the investigation results of R&D related to SMR in Japan, focusing on the EGSMR activities (2022-2023), are summarized. The target of this report is to provide useful information for future discussions on international cooperation concerning SMR as well as nuclear power field human resources development internationally and domestically.

JAEA Reports

Opposing mixed convection heat transfer for turbulent single-phase flows (Contract research, Translated document)

Motegi, Kosuke; Shibamoto, Yasuteru; Hibiki, Takashi*; Tsukamoto, Naofumi*; Kaneko, Junichi*

JAEA-Review 2024-039, 45 Pages, 2024/09

JAEA-Review-2024-039.pdf:2.23MB

Several heat transfer correlations have been reported related to single-phase opposing flow; however, these correlations are based on experiments conducted in various channel geometries, working fluids, and thermal flow parameter ranges. Therefore, establishing a guideline for deciding which correlation should be selected based on its range of applicability and extrapolation performance is important. This study reviewed the existing heat transfer correlations for turbulent opposing-flow mixed convection. Furthermore, the authors evaluated the predictive performance of each correlation by comparing them with the experimental data obtained under various experimental conditions. The Jackson and Fewster, Churchill, and Swanson and Catton correlations can accurately predict all the experimental data. The authors confirmed that heat transfer correlations using the hydraulic-equivalent diameter as a characteristic length can be used for predictions regardless of channel-geometry differences. Furthermore, correlations described based on nondimensional dominant parameters can be used for predictions regardless of the differences in working fluids.

JAEA Reports

Investigation on partitioning and utilization of valuable elements and radio isotopes from spent nuclear fuel

Saga, Kaname

JAEA-Review 2024-038, 9 Pages, 2024/09

JAEA-Review-2024-038.pdf:0.88MB

The purpose of this report is understanding the elements and radio isotopes with highly useful based on the current trends in the industrial field. The survey was conducted from the viewpoint of the abundance of elements and radio isotopes contained and the demand in the industrial field, and the following survey results were obtained. The economic scale of radio isotopes in the industrial field (including radiation use) has been increasing in recent years in the manufacturing, medical, and agricultural sectors. On the other hand, the domestic production of the utilized radio isotope is still small, and some radio isotopes are entirely imported. Radio isotopes such as Sr-90, Mo-100, Cs-137, and Am-241 from spent fuel are suitable for industrial use because of their abundance in spent fuel and half-lives. As for the utilization of elements, the industrial use of platinum group elements and rare earth elements were explored because these elements are high industrial value and low domestic self-sufficiency. The platinum group elements were evaluated to have the potential to be supplied in a certain amount as a new domestic production source based on their abundance in spent fuel. On the other hand, for rare earth elements, which have also low self-sufficiency rate, the ratio of the amount that could be supplied from spent fuel compared to the current annual supply was evaluated to be less than 1%, and therefore, no effect could be expected. The domestic recycling rate of rare earth elements is low, and the provision of numerical simulation technology, which improves the recycling rate, could highly contribute to the industries. This technology makes it possible to calculate the optimal operating conditions for the separation process, such as the number of processing stages and processing speed, in accordance with the elements to be separated and used.

JAEA Reports

Survey of asbestos in piping insulation in specified facilities of JMTR

Kuwabara, Ryota; Yanai, Tomohiro; Kagi, Takumi; Tanimoto, Masataka

JAEA-Review 2024-036, 43 Pages, 2024/09

JAEA-Review-2024-036.pdf:4.18MB

The Japan Materials Testing Reactor (JMTR) has a main facility and a specified facility, and construction began in 1967. Therefore, there is concern that asbestos was used in various parts of the facility since it was built before asbestos was regulated. Asbestos has very good properties such as durability, heat resistance, chemical resistance, and electrical insulation, and there is a high probability that asbestos was contained in components and building materials at that time. Therefore, the investigation was focused on specified facilities outside the controlled areas, and an investigation was conducted on heat insulators wrapped around piping installed in the facilities.Of the various systems of piping installed in the facilities, we investigated the presence or absence of asbestos in the heat insulators, especially in piping that had been installed for a long period of time. Inhalation of asbestos can cause diseases such as lung cancer and mesothelioma, so when buildings are demolished or renovated, there is a legal requirement to conduct a preliminary investigation to determine the presence of asbestos. Therefore, it is important to understand the status of asbestos usage within the facility in advance, and we believe that it can also be applied to the formulation of plans for the dismantling and removal of equipment and devices during future decommissioning. As a result of the investigations, asbestos was found in the thermal insulation, especially in the elbow where the piping is bent. The results of these investigations are presented in this report.

JAEA Reports

Horonobe Underground Research Laboratory Project; Investigation program for the fiscal year 2024

Nakayama, Masashi

JAEA-Review 2024-033, 64 Pages, 2024/09

JAEA-Review-2024-033.pdf:5.15MB

The Horonobe Underground Research Laboratory Project is being pursued by the Japan Atomic Energy Agency to enhance the reliability of relevant technologies for geological disposal of high-level radioactive waste through investigating the deep geological environment within the host sedimentary rocks at Horonobe Town in Hokkaido, north Japan. In the fiscal year 2024, we continue R&D on "Study on near-field system performance in geological environment", "Demonstration of repository design options", and "Understanding of buffering behaviour of sedimentary rocks to natural perturbations". These are identified as key R&D challenges to be tackled in the Horonobe underground research plan for the fiscal year 2020 onwards. In the "Study on near-field system performance in geological environment", we continue to obtain data from the full-scale engineered barrier system performance experiment, and work on the specifics of the full-scale engineered barrier system dismantling experiment. We summarise the solute transport experiments for the excavation damaged zone and the effects of organic matter, micro-organisms and colloids, and develop the assessment methodology. We summarise the evaluation methodology using the deep Wakkanai Formation as a case study for block-scale solute transport experiments. As for "Demonstration of repository design options", we summarise the results of investigations and experiments on changes in the geological environment after tunnel excavation and closure, and summarise the applicability and technical challenges of the closure technology for boreholes excavated from tunnels. The systematic integration of technologies towards EBS emplacement, including the organisation of investigation and evaluation methods and analysis, will be promoted. Experiments to confirm the performance of the engineered barrier system under critical conditions, such as high temperatures ($$>$$100$$^{circ}$$C), continue the in-situ tests started in 2023.

JAEA Reports

Update of conceptual design of Near Surface Disposal Facilities of Radioactive Wastes Generated from Research, Industrial and Medical Facilities

Iwamura, Toko; Nakata, Hisakazu; Maekawa, Keisuke; Sakai, Akihiro; Sakamoto, Yoshiaki

JAEA-Review 2024-032, 39 Pages, 2024/09

JAEA-Review-2024-032.pdf:6.5MB

Japan Atomic Energy Agency (JAEA) is responsible for the disposal of low-level radioactive waste generated by JAEA itself and research facilities under the revised JAEA Act of 2008 and subsequently developed a "Plan for the Implementation of Disposal Operations" (implementation plan) in 2009. Furthermore, based on the results of the survey on the amount of waste generated by research facilities, the quantity of wastes for the near surface disposal was set at 600,000 in terms of 200L drums, and the results of the consideration on the conceptual design of the disposal facility were summarized in 2012. In 2018 JAEA published its long-term outlook and policy regarding back-end measures in "Back-end Roadmap", and in this "Back-end Roadmap", the amount of waste generated by JAEA was also organized and published. Therefore, the amount of waste materials from waste generators outside JAEA was re-examined, and as a result, the size of the burial facility was changed from 600,000 to 750,000 in terms of 200L drums, and approval was obtained for a change in the implementation plan. In addition, the conceptual design of the disposal facility was revised to accommodate the increased size of the facility. This report summarizes the results of the updated assumptions and disposal facility design from the 2012 conceptual design.

JAEA Reports

Establishment of characterization method for small fuel debris using the world's first isotope micro imaging apparatus (Contract research); FY2022 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Kogakuin University*

JAEA-Review 2024-015, 99 Pages, 2024/09

JAEA-Review-2024-015.pdf:5.42MB

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 "Establishment of characterization method for small fuel debris using the world's first isotope micro imaging apparatus" conducted in FY2022. 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

Challenge of novel hybrid-waste-solidification of mobile nuclei generated in fukushima nuclear power station and establishment of rational disposal concept and its safety assessment (Contract research); FY2022 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Tokyo Institute of Technology*

JAEA-Review 2024-012, 122 Pages, 2024/09

JAEA-Review-2024-012.pdf:6.31MB

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 (hereafter referred to "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 "Challenge of novel hybrid-waste-solidification of mobile nuclei generated in Fukushima Nuclear Power Station and establishment of rational disposal concept and its safety assessment" conducted in FY2022. The present study aims to establish the rational waste disposal concept of a variety of wastes generated in 1F based on the hybrid-waste-solidification by the Hot Isostatic Press (HIP) method. The ceramics form with target elements, mainly iodine, which is difficult to immobilize, and Minor actinides such as Am, an alphaemitter and heat source, are HIPed with well-studied materials such as SUS and zircaloy, which make the long-term stability evaluation and safety assessment possible.

JAEA Reports

Quantitative evaluation of long-term state changes of contaminated reinforced concrete considering the actual environments for rational disposal (Contract research); FY2022 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; The University of Tokyo*

JAEA-Review 2024-011, 121 Pages, 2024/09

JAEA-Review-2024-011.pdf:5.42MB

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 "Quantitative evaluation of long-term state changes of contaminated reinforced concrete considering the actual environments for rational disposal" conducted from FY2020 to FY2022. Estimating waste volume and concentration is essential for decommissioning concrete structures at the Fukushima Daiichi Nuclear Power Station.

JAEA Reports

Nuclear fuel storage container opening inspection and metal inner container repacking

Licensing Application Group, Fuels and Materials Department

JAEA-Testing 2024-002, 20 Pages, 2024/08

JAEA-Testing-2024-002.pdf:1.46MB

The contamination accident occurred at Plutonium Fuel Research Facility (PFRF) in Japan Atomic Energy Agency (JAEA) Oarai Research and Development Institute on June 6, 2017. During the work of opening the fuel storage container and checking the properties of the contents, the plastic bag that double-packed the inner container burst. The scattering of the fuels contaminated the work room and exposed the worker. The cause of the plastic bag burst was that the enclosed epoxy resin was decomposed by $$alpha$$-rays and the internal pressure increased due to the generated hydrogen gas. The 54 storage containers containing plutonium held at PFRF also at risk of increasing internal pressure. Therefore, an opening inspection was conducted to confirm the contents of the storage container in the hot cell. In addition, the contents of storage containers that may generate gas were stabilized. We are planning to transport the fuel storage containers out to another facility for the decommission of PFRF. The other 9 storage containers include oxide raw material powder: Pu + $$^{235}$$U in excess of 220 g. In order to decrease to less than 220 g (the limit of transport cask), the metal inner containers in the storage container were taken out and repacked in another storage container. This report describes advance measures such as permit application and the details of about storage container opening inspection and metal inner container repacking.

JAEA Reports

Manuals for resonance analysis code for neutron IMaging "RAIM"

Hasemi, Hiroyuki; Kai, Tetsuya

JAEA-Testing 2024-001, 39 Pages, 2024/08

JAEA-Testing-2024-001.pdf:1.4MB

RAIM is an analysis code that analyzes resonance absorption spectra measured at pulsed neutron sources such as the Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex (J-PARC) to obtain information on nuclear densities and temperatures. By calculating the convolution of the pulse functions of neutron beam and the resonance capture function that is based on the nuclear cross section data, RAIM reproduces the resonance absorption spectrum measured by a pulsed neutron source. Then, RAIM determines the density and temperature of specific nuclides in a sample by performing spectral fitting on the resonance absorption spectrum data. In addition, RAIM is developed to facilitate the analysis of resonance imaging data by minimizing the number of parameters for calculation setup and by providing scripts for processing many resonance absorption spectra measured by a two-dimensional detector at once. This manual explains how to install RAIM on a computer and how to simulate resonance absorption spectra and fit them to measured data.

JAEA Reports

Research on radioactive aerosol control and decontamination at Fukushima Daiichi Nuclear Power Station Decommissioning (Contract research); FY2022 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; The University of Tokyo*

JAEA-Review 2024-031, 75 Pages, 2024/08

JAEA-Review-2024-031.pdf:3.74MB

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 "Research on radioactive aerosol control and decontamination at Fukushima Daiichi Nuclear Power Station decommissioning" conducted in FY2022. The present study aims to develop a safe laser decontamination system that can control aerosol diffusion during laser decontamination while simultaneously allowing advanced particle measurement and evaluation, in cooperation with a research group in the United Kingdom.

JAEA Reports

Investigation of asbestos at hot laboratory; Investigation of asbestos in heat insulation material

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 stat us 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.

JAEA Reports

Annual report of Department of Research Reactor and Tandem Accelerator, JFY2022 (Operation, Utilization and Technical Development of JRR-3, NSRR, Tandem Accelerator, Radio Isotope Production Facility and Tritium Process Laboratory, Decommissioning Activity for JRR-4)

Department of Research Reactor and Tandem Accelerator

JAEA-Review 2024-029, 107 Pages, 2024/08

JAEA-Review-2024-029.pdf:5.18MB

The Department of Research Reactor and Tandem Accelerator is in charge of the operation, utilization and technical development of JRR-3 (Japan Research Reactor No.3), NSRR (Nuclear Safety Research Reactor), Tandem Accelerator, Radio Isotope Production Facility, and TPL (Tritium Process Laboratory). Also decommissioned JRR-4 (Japan Research Reactor No.4) and maintains JRR-1 (Japan Research Reactor No.1) and the FEL (Free Electron Laser). This annual report describes the activities of our department in fiscal year of 2022. We carried out the operation and maintenance, utilization, upgrading of utilization techniques, decommissioned JRR-4, safety administration, international cooperation and human resources development. Also contained are lists of publications, meetings, granted permissions on laws and regulations concerning atomic energy, outcomes in service and technical developments and so on.

JAEA Reports

Clarification of debris formation conditions on the basis of the sampling data and experimental study using simulated fuel debris and reinforcement of the analytical results of severe accident scenario (Contract Research); FY2022 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; University of Fukui*

JAEA-Review 2024-014, 112 Pages, 2024/08

JAEA-Review-2024-014.pdf:8.22MB

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 "Clarification of debris formation conditions on the basis of the sampling data and experimental study using simulated fuel debris and reinforcement of the analytical results of severe accident scenario" conducted in FY2022. The present study aims to clarify the debris formation mechanism and utilize the results to refine the accident scenario. In the backward analysis of oxide debris formation, we succeeded in the formation of simulated fuel particle by the aerodynamic levitation method and ejection of melted oxides from tungsten pipe with a small hole. And we demonstrated the formation of simulated fuel debris of U1-No.15 obtained by the sampling in 1F.

JAEA Reports

Uncertainty reduction of the FPs transport mechanism and debris degradation behavior and evaluation of the reactor contamination of debris state on the basis of the accident progression scenario of fukushima daiichi nuclear power station unit 2 and 3 (Contract research); FY2022 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Tokyo Institute of Technology*

JAEA-Review 2024-010, 112 Pages, 2024/08

JAEA-Review-2024-010.pdf:6.49MB

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 "Uncertainty reduction of the FPs transport mechanism and debris degradation behavior and evaluation of the reactor contamination of debris state on the basis of the accident progression scenario of Fukushima Daiichi Nuclear Power Station Unit 2 and 3" conducted in FY2022. The present study aims to elucidate the cause of the high dosage under shield plug by clarification of to the cesium behavior of migration, adhesion to structure and deposition as well as evaluate the properties of metal-rich debris predeceasing melted through the materials science approach based on the most probable scenario of accident progression of Unit 2 and 3. In this fiscal year, the followings were achieved.

JAEA Reports

Trial analysis of chemical behavior in high-level radioactive liquid waste tank at accident of evaporation to dryness by boiling of reprocessing plant

Yoshida, Kazuo; Hiyama, Mina*; Tamaki, Hitoshi

JAEA-Research 2024-007, 24 Pages, 2024/08

JAEA-Research-2024-007.pdf:2.1MB

An accident of evaporation to dryness by boiling of high-level radioactive liquid waste (HLLW) is postulated as one of the severe accidents caused by the loss of cooling function at a fuel reprocessing plant. In this case, volatile radioactive materials, such as ruthenium (Ru) are released from the tanks with water and nitric-acid mixed vapor into the atmosphere. Accurate quantitative estimation of released Ru is one of the important issues for risk assessment of those facilities. It has been observed experimentally that volatility of RuO$$_{4}$$ is suppressed by HNO$$_{2}$$ generated by HNO$$_{3}$$ radiolysis. The analysis of chemical reactions of NO$$_{x}$$ including HNO$$_{3}$$ and HNO$$_{2}$$ in the waste tank is essential to simulate of these phenomena. To resolve this issue, an analytical approach has been attempted to couple dynamically two computer codes SHAWED and SCHERN. The simulation of boiling behavior in the tank is conducted with SHAWED. SCHERN simulates chemical behaviors of HNO$$_{3}$$, HNO$$_{2}$$ and NO$$_{x}$$ in the tank. A programmatic coupling algorithm and a trial simulation of the accident are presented in this report.

JAEA Reports

Extension of the ACE file perturbation tool in FRENDY; Implementation of the perturbation method for the elastic scattering angle distribution based on the maximum entropy method

Maruyama, Shuhei

JAEA-Data/Code 2024-009, 16 Pages, 2024/08

JAEA-Data-Code-2024-009.pdf:1.08MB

The Japanese nuclear data processing code FRENDY implements the ACE file perturbation tool based on the random sampling method, which can be used to quantify nuclear data-induced uncertainties. However, it has not been able to evaluate the uncertainty due to the scattering angle distribution, which is not ignored in the uncertainty quantification of fast reactor core analysis and shielding analysis. Recently, a method to quantify the uncertainty based on the maximum entropy method has been proposed by the authors. In this report, a perturbation function for the uncertainty of the elastic scattering angular distribution based on this proposed method has been added to the FRENDY/ACE file perturbation tool.

JAEA Reports

Dataset of nuclide production from nuclear capture reaction of negative muon based on Monte Carlo simulation

Yamaguchi, Yuji; Harada, Masahide; Haga, Katsuhiro

JAEA-Data/Code 2024-008, 91 Pages, 2024/08

JAEA-Data-Code-2024-008.pdf:1.24MB
JAEA-Data-Code-2024-008-appendix(CD-ROM).zip:0.09MB

We have produced a dataset of the yields of radionuclides produced by the nuclear capture of negative muons applying Monte Carlo calculation due to scarce experimental data for the sake of radiation safety of experimental facilities which can provide negative muons. The dataset covers all the stable targets of natural elements. The use of the dataset is described in an example of radioactive estimation for a negative-muon-irradiated sample. The dataset reported is fundamental data expected to be utilized in experiments with negative muons of various fields including radiation safety.

JAEA Reports

Report of summer holiday practical training on 2023

Ishitsuka, Etsuo; Nagasumi, Satoru; Hasegawa, Toshinari; Kawai, Hiromi*; Wakisaka, Shinji*; Nagase, Sota*; Nakamura, Kento*; Yaguchi, Hiroki*; Ishii, Toshiaki; Nakano, Yumi*; et al.

JAEA-Technology 2024-008, 23 Pages, 2024/07

JAEA-Technology-2024-008.pdf:1.69MB

Five people from three universities participated in the 2023 summer holiday practical training with the theme of "Technical development on HTTR". The participants practiced the analysis of HTTR core, the analysis of behavior on loss of forced cooling test, the analysis of Iodine deposition behavior in primary cooling system and the feasibility study of energy storage system for HTGRs. In the questionnaire after this training, there were impressions such as that it was useful as a work experience and some students found it useful for their own research. These impressions suggest that this training was generally evaluated as good.

23042 (Records 1-20 displayed on this page)