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Journal Articles

Leaching behavior of prototypical Corium samples; A Step to understand the interactions between the fuel debris and water at the Fukushima Daiichi reactors

Nakayoshi, Akira; Jegou, C.*; De Windt, L.*; Perrin, S.*; Washiya, Tadahiro

Nuclear Engineering and Design, 360, p.110522_1 - 110522_18, 2020/04

 Times Cited Count:0

JAEA Reports

Post-processor coding for large-scale transient simulation computer codes

Yoshikawa, Shinji

JAEA-Technology 2019-024, 22 Pages, 2020/03

JAEA-Technology-2019-024.pdf:1.76MB
JAEA-Technology-2019-024-appendix(CD-ROM).zip:73.55MB

In various technical fields of nuclear energy, computer codes are often used for transient simulations of target phenomena. Some of the codes were developed many years ago and have been revised with newly acquired findings, rather than newly developed, because of many encompassed numerical models and complexity of algorithms. In many cases, available outputs for users are output text files and graphs showing temporal variations of parameters, despite diversified and huge number of output information items are posing difficulty to the users in grasping the whole picture of the reproduced phenomena. This report compiles a series of know-hows in building a post-processor software for large simulation codes which serves as an interactive tool for code users in understanding the reproduced consequence with visually understandable information items. These know-hows are acquired through post-processor developments for LWR severe accident simulation codes RELAP/SCDAPSIM and MELCOR.

JAEA Reports

Investigations on distribution of radioactive substances owing to the FDNPP accident in the fiscal year 2018 (Contract research)

Group for Fukushima Mapping Project

JAEA-Technology 2019-019, 135 Pages, 2020/03

JAEA-Technology-2019-019.pdf:22.01MB

After the accident at TEPCO Fukushima Daiichi Nuclear Power Station (FDNPS), distribution situation survey on radioactive materials have been conducted with financially supported by the Ministry of Education, Culture, Sports, Science and Technology (later the Nuclear Regulatory Agency) from June 2011 to FY2018. Results obtained in the project in FY2018 are presented in this report. Car-borne surveys, a flat ground measurement using survey meters, a walk survey and an unmanned helicopter survey were carried out to obtain air dose rate data. Air dose rate distribution maps were created and temporal changes of air dose rate were analyzed. Regarding radiocesium deposition in the soil, depth profile survey in the soil and in-situ measurement were performed. Based on these measurement results, effective half-life of the air dose rate and the deposition were evaluated. Considering radiation monitoring data obtained in previous surveys and the installation positions of existing monitoring posts, we tried to make the "score" of the importance of measurement points. Using the Bayesian hierarchical modeling approach, we obtained a map that integrated the air dose rate distribution data obtained from aircraft monitoring, car-borne surveys, and walk surveys for the entire region within 80 km from the FDNPS. The measurement results for FY2018 were published on the "Expansion Site of Distribution Map of Radiation Dose", and measurement data were stored as CSV format. Radiation monitoring and environmental sample analysis owing to the comprehensive radiation monitoring plan were carried out.

JAEA Reports

Influence factors on temperature behavior of robot test pool

Arakawa, Ryoki; Nosaki, Nobuhisa

JAEA-Technology 2019-018, 157 Pages, 2020/03

JAEA-Technology-2019-018.pdf:12.97MB

The Naraha Center for Remote Control Technology Development has various test facilities for the decommissioning work after the accident of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, and is now promoting external use. In the test facilities, the robot test pool for the underwater robot can be used in different temperature conditions from room temperature to 60$$^{circ}$$C, maximum setting temperature. In order to clarify the temperature behavior in heating condition, a heating test from room temperature to 60$$^{circ}$$C was performed. The data was obtained this way. From the data, a heat transfer model for evaluating the temperature behavior was investigated, and the temperature evaluation method for the robot test pool was developed. By using the developed evaluation method, the influence of various factors such as flow rate and humidity on the temperature behavior was investigated for the condition of temperature heating, holding (test condition) and cooling. From the investigation, the temperature behavior of the robot test pool was analytically clarified, and a reasonable operation method was proposed. This report summarizes the results of analytical study at the temperature heating, holding and cooling condition.

JAEA Reports

Annual report for FY2018 on the activities of Naraha Center for Remote Control Technology Development (April 1, 2018 - March 31, 2019)

Hanari, Toshihide; Furukawahara, Ryo; Tsuchida, Yoshihiro; Kawabata, Kuniaki; Chiba, Yusuke

JAEA-Review 2019-047, 32 Pages, 2020/03

JAEA-Review-2019-047.pdf:2.45MB

Naraha Center for Remote Control Technology Development (Naraha Center) was established in Japan Atomic Energy Agency to promote a decommissioning work of Fukushima Daiichi Nuclear Power Station (Fukushima Daiichi NPS). Naraha Center consists of a Full-scale Mock-up Test Building and Research Management Building, and various test facilities are installed in them for the decommissioning work of Fukushima Daiichi NPS. The number of facility use in Naraha Center was 64 in FY2018. This report summarizes the activities of Naraha Center in FY2018, such as the utilization of facilities and equipment of Naraha Center, the development of remote control technologies for supporting the decommissioning work, maintenance of the remote control machines for emergency response, and training for operators by using the machines.

JAEA Reports

Development of thin SiC neutron detector with high radiation resistance (Contract research); FY2018 Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development

Collaborative Laboratories for Advanced Decommissioning Science; Kyoto University*

JAEA-Review 2019-042, 43 Pages, 2020/03

JAEA-Review-2019-042.pdf:25.64MB

JAEA/CLADS, had been conducting the Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development (hereafter referred to "the Project") in FY2018. The Project aims to contribute to solving problems in nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. 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. Among the adopted proposals in FY2018, this report summarizes the research results of the "Development of Thin SiC Neutron Detector with High Radiation Resistance". In the works for debris retrieval, it is required to install subcritical surveillance radiation monitors that can surely work for long time under extremely high gamma-ray radiation environment. However, there have been problems such as remote control of conventional radiation monitors is difficult because heavy radiation shields are needed. In the present study, we will develop a neutron detector using thin, light-weight and radiation-resistive silicon carbide (SiC) that has low sensitivity to gamma-rays as well as the data collection system in collaboration with the U.K. Using this system, the performance tests will be conducted supposing the real debris retrieval including the irradiation tests. Based on the results, we will conduct research and development aiming to make the system ready for use in real decommissioning works.

JAEA Reports

Contribution to risk reduction in decommissioning works by the elucidation of basic property of radioactive microparticles (Contract research); FY2018 Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development

Collaborative Laboratories for Advanced Decommissioning Science; Ibaraki University*

JAEA-Review 2019-041, 71 Pages, 2020/03

JAEA-Review-2019-041.pdf:3.38MB

JAEA/CLADS, has been conducting the Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development (hereafter referred to "the Project") since FY2018. The Project aims at solving problems in nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. For this purpose, intelligence has been collected from all over the world, and basic research and human resource development have been promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. Among the adopted proposals in FY2018, this report summarizes the research results of the "Contribution to Risk Reduction in Decommissioning Works by the Elucidation of Basic Property of Radioactive Microparticles". In order to establish the decommissioning procedures (recovery of the melted fuels, decontamination inside the reactors, ensuring the safety of the workers, etc.) of the Fukushima Daiichi Nuclear Power Station, radioactive microparticles released by the accident are an important information source for clarifying what had happened inside the reactors in the course of the accident. The purpose of the present study is to obtain detailed knowledge on the basic properties (particle size, composition, electrical/optical properties, etc.) of the radioactive microparticles, as well as to further elucidate the various properties of the radioactive microparticles including the quantitative evaluation of alpha-ray-emitters, through the Japan-UK synergetic research. Thus, we are conducting research and development that will contribute to the comprehensive works towards the risk reduction in the "decommissioning" plan.

JAEA Reports

Research and development of radiation-resistant sensor for fuel debris by integrating advanced measurement technologies (Contract research); FY2018 Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development

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

JAEA-Review 2019-040, 77 Pages, 2020/03

JAEA-Review-2019-040.pdf:4.61MB

JAEA/CLADS, had been conducting the Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development (hereafter referred to "the Project") in FY2018. The Project aims to contribute to solving problems in nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. 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 FY2018, this report summarizes the research results of the "Research and Development of Radiation-resistant Sensor for Fuel Debris by Integrating Advanced Measurement Technologies". The present study aims to in-situ measure and analyze the distribution status and criticality of flooded fuel debris. For this purpose, we construct a neutron measurement system by developing compact diamond neutron sensor (200 $$mu$$m $$times$$ 510 $$mu$$m thickness) and integrated circuit whose radiation resistance was improved by circuit design. Along with the multi-phased array sonar and the acoustic sub-bottom profiling (SBP) system, the neutron measurement system will be installed in the ROV (developed by Japan-UK collaboration) and its demonstration tests will be conducted in a PCV mock-up water tank.

JAEA Reports

Research and development of transparent materials for radiation shield using nanoparticles (Contract research); FY2018 Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development

Collaborative Laboratories for Advanced Decommissioning Science; Kyushu University*

JAEA-Review 2019-039, 104 Pages, 2020/03

JAEA-Review-2019-039.pdf:5.57MB

The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development (hereafter referred to "the Project") in FY2018. The Project aims to contribute to solving problems in nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. 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 FY2018, this report summarizes the research results of the "Research and Development of Transparent Materials for Radiation Shield using Nanoparticles". The present study aims to reduce radiation exposure of workers in debris retrieval/analysis and reduce deterioration of optical and electronic systems in remote cameras. For these purposes, we develop transparent radiation shield by making the shield materials into nanoparticles, and dispersing/solidifying them in epoxy resin. By making B$$_{4}$$C and W into nanoparticles, we will also develop a radiation shield that shields both neutrons and gamma-rays, and also suppresses secondary gamma-rays produced from neutrons.

JAEA Reports

Development of imaging system with ultra-high spatial resolution aiming to detect alpha-dust (Contract research); FY2018 Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development

Collaborative Laboratories for Advanced Decommissioning Science; Tohoku University*

JAEA-Review 2019-038, 57 Pages, 2020/03

JAEA-Review-2019-038.pdf:4.6MB

JAEA/CLADS, had been conducting the Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development (hereafter referred to "the Project") in FY2018. The Project aims to contribute to solving problems in nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. 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. Among the adopted proposals in FY2018, this report summarizes the research results of the "Development of Imaging System with Ultra-high Spatial Resolution Aiming to Detect Alpha-dust". In the present study, we have developed a prototype of a system aiming to elucidate the behavior of alpha-dust generated at the time of debris retrieval. In this system, alpha-ray is first converted to visible light by novel scintillator. Then, imaging with ultra-high resolution will be possible using a lens and an Si-semiconductor camera (CMOS camera). Also, it will be possible to identify the species of alpha-ray emitting nuclides by unfolding of the spectra. The demonstration tests of the system will be conducted for dust samplers at the Plutonium Fuel Development Center, JAEA. In the development of the present system, it is important to use scintillator whose emission wavelength is sensitive to the CMOS camera as well as high emission scintillator. Considering these conditions, the key technology will be the improvement of the purity of crystals and optimization of the shapes of the materials including powers.

JAEA Reports

Development of technology to prevent scattering of radioactive materials in fuel debris retrieval (Contract research); FY2018 Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development

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

JAEA-Review 2019-037, 90 Pages, 2020/03

JAEA-Review-2019-037.pdf:7.0MB

JAEA/CLADS, had been conducting the Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development (hereafter referred to "the Project") in FY2018. The Project aims to contribute to solving problems in nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. 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 FY2018, this report summarizes the research results of the "Development of Technology to Prevent Scattering of Radioactive Materials in Fuel Debris Retrieval". The objective of the present study is to clarify the behavior of microparticles in gas and liquid phases in order to steadily confine radioactive microparticles at the time of debris retrieval in Fukushima Daiichi Nuclear Power Station. In addition, as measures to prevent scattering, we will evaluate and develop methods by experiments and simulation as to; (1) a method to suppress the scattering with minimum amount of water utilizing water spray etc., and (2) a method to suppress the scattering by solidifying fuel debris.

JAEA Reports

Quantitative analysis method for radiation distribution in high radiation environment by gamma-ray image spectroscopy (Contract research); FY2018 Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development

Collaborative Laboratories for Advanced Decommissioning Science; Kyoto University*

JAEA-Review 2019-036, 65 Pages, 2020/03

JAEA-Review-2019-036.pdf:4.46MB

JAEA/CLADS, had been conducting the Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development (hereafter referred to "the Project") in FY2018. The Project aims to contribute to solving problems in nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. 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 FY2018, this report summarizes the research results of the "Quantitative Analysis Method for Radiation Distribution in High Radiation Environment by Gamma-ray Image Spectroscopy". Electron-tracking Compton camera (ETCC) has been developed originally for nuclear gamma-ray astronomy, and also applied to medical use as a technology that greatly improves the resolution of conventional Compton camera by measuring three-dimensional tracking of electrons using a gaseous 3-dimensional position detector (so called Time Projection Chamber) in the first stage. In the present study, based on the ETCC that has been developed for medical use, we produce a prototype of light weight ETCC with the emphasis on the operability at the site, and evaluate its practicability by field tests.

JAEA Reports

Basic research on the stability of fuel debris including alloy phase (Contract research); FY2018 Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development

Collaborative Laboratories for Advanced Decommissioning Science; Tohoku University*

JAEA-Review 2019-035, 61 Pages, 2020/03

JAEA-Review-2019-035.pdf:2.9MB

JAEA/CLADS, had been conducting the Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development (hereafter referred to "the Project") in FY2018. The Project aims to contribute to solving problems in nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. 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 FY2018, this report summarizes the research results of the "Basic Research on the Stability of Fuel Debris Including Alloy Phase". In the present study, we focus on fuel debris consisting of oxide phase and alloy phase generated by the high-temperature chemical reaction between structure materials (SUS pipes, pressure vessels, etc.) and fuels (melted fuels, claddings components, etc.). We synthesize the simulated debris of UO$$_{2}$$-SUS system and UO$$_{2}$$-Zr(ZrO$$_{2}$$)-SUS system by high-temperature heat treatment, and measure their chemical property and dissolution behavior in water. Also, we will conduct research and development to spectroscopically analyze secular changes of oxide phase and alloy phase in the simulated debris.

JAEA Reports

Analysis of microparticles generated by laser processing and development of a methodology for their nuclear identification (Contract research); FY2018 Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development

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

JAEA-Review 2019-034, 59 Pages, 2020/03

JAEA-Review-2019-034.pdf:3.15MB

JAEA/CLADS, conducted the Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development (hereafter referred to "the Project") in FY2018. The Project aimed to contribute to solving problems in the field of nuclear energy represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. For this purpose, intelligence was collected from all over the world, and basic research and human resource development was promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barriers of conventional organizations and research fields. Among the adopted proposals in FY2018, this report summarizes the research results of the "Analysis of microparticles generated by laser processing and development of a methodology for their nuclear identification". Although laser processing has various advantages, one well-known disadvantage is that it generates a large amount of microparticles during the processing. Therefore, the application of laser processing to decommissioning waste contaminated with radioactive materials has been hesitant because the mechanism generating the microparticles has not been fully understood. In this study, the mechanism of microparticle production by laser processing is investigated from fundamentals. Also, we develop a laser on-line principle device to examine the nuclides present in the microparticles that are produced, based on the measurement of the particle size distribution by collecting the microparticles using aerodynamic lenses.

JAEA Reports

Development of dosimeter for severe radiation environment near reactor pressure vessel (Contract research) ;FY2018 Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development

Collaborative Laboratories for Advanced Decommissioning Science; National Institute of Technology, Kisarazu College*

JAEA-Review 2019-033, 57 Pages, 2020/03

JAEA-Review-2019-033.pdf:3.17MB

JAEA/CLADS, had been conducting the Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development (hereafter referred to "the Project") in FY2018. The Project aims to contribute to solving problems in nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. 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. Among the adopted proposals in FY2018, this report summarizes the research results of the "Development of Dosimeter for Severe Radiation Environment near Reactor Pressure Vessel". Since the radiation level in the reactors and buildings of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. (1F) is extremely high due to the accident, it is required to develop radiation measurement technology based on the needs at the 1F working site. In the previous studies, it has been verified that dosimeters using solar cell devices can be used for dose evaluation under high dose rate near the reactor pressure vessel because they have advantages such as unnecessity of a high-voltage source, ultra-compactness, lightweight, and high radiation resistance. Through this study, we will develop technologies towards practical application of revolutionary radiation measurement system based on the dose measurement technology utilizing solar cell devices.

JAEA Reports

Identification of altered phases of fuel debris by laser fluorescence spectroscopy (Contract research); FY2018 Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development

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

JAEA-Review 2019-030, 66 Pages, 2020/03

JAEA-Review-2019-030.pdf:7.11MB

JAEA/CLADS, had been conducting the Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development (hereafter referred to "the Project") in FY2018. The Project aims to contribute to solving problems in nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. 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. Among the adopted proposals in FY2018, this report summarizes the research results of the "Identification of Altered Phases of Fuel Debris by Laser Fluorescence Spectroscopy". In the present study, we focus on uranium that is the main component element in debris, and identify the altered phase produced on the debris surface under various conditions by time-resolved laser fluorescence spectroscopy (TRLFS) with high sensitivity to hexavalent uranium (U(VI)) that is stable in oxidation environment. In particular, further high-sensitive and high-resolution measurements are implemented by improving the fluorescence yields and suppressing the broadening of the peaks through the measurements at ultra-low temperature. In addition, with the supports by quantum chemical calculations, multivariate analysis, and machine learning, the method will lead to the identification of multicomponent and heterogeneous altered phase of fuel debris.

JAEA Reports

Measurement of plutonium spectrum using laser induced breakdown spectroscopy; High resolution spectroscopy (350-670nm)

Akaoka, Katsuaki; Oba, Masaki; Miyabe, Masabumi; Otobe, Haruyoshi; Wakaida, Ikuo

JAEA-Research 2020-001, 142 Pages, 2020/03

JAEA-Research-2020-001.pdf:4.0MB

Laser Induced Breakdown Spectroscopy (LIBS) method is an attractive technique because real-time, in-situ and remote elemental analysis is possible without any sample preparation. The LIBS technique can be applied for analyzing elemental composition of samples under severe environments such as the estimation of impurities in the next generation nuclear fuel material containing minor actinide (MA) and the detection of fuel debris in the post-accident nuclear core reactor of TEPCO's Fukushima Daiichi Nuclear Power Station. For applying LIBS to the analysis of nuclear fuel materials, it is indispensable to identify the emission spectrum and its intensity on impurities intermingled within complex emission spectra of matrix elements such as uranium (U) and plutonium (Pu). In the present study, an echelle spectrometer with a resolving power of 50,000 was employed to identify spectra of plutonium of wavelength ranging from 350 to 670nm. The 465 atomic spectra and 341 ionic spectra can be identified. We have confirmed that the measured wavelength of spectra is consistent with published values.

JAEA Reports

Decontamination simulation and future prediction of air dose rate in difficult to return zone in Fukushima Prefecture

Yamashita, Takuya; Sawada, Noriyoshi*

JAEA-Research 2019-010, 227 Pages, 2020/03

JAEA-Research-2019-010.pdf:21.44MB

In order to support the decontamination activities proceeded by the national government and municipalities in terms of technology, we have developed a simulation system "RESET" which predicts the effect of decontamination. We also developed a "two-component model" for the purpose of predicting long-term changes in the air dose rate. We use these tools to perform decontamination simulation and predictive analysis of the air dose rate after decontamination, and provide information to the national government and municipalities aiming for reconstruction. In this report, the verification result of the prediction methods implemented using actual measurement data obtained in the "Decontamination model demonstration project in difficult-to-return zone" and "Survey result on transition of air dose rate after decontamination model demonstration project" conducted by Ministry of the Environment. In addition, the decontamination simulation conducted for the entire difficult-to-return area and the results of future prediction of the air dose rate after decontamination are shown.

JAEA Reports

Fission product chemistry database ECUME version 1.1

Development Group for LWR Advanced Technology

JAEA-Data/Code 2019-017, 59 Pages, 2020/03

JAEA-Data-Code-2019-017.pdf:3.26MB
JAEA-Data-Code-2019-017-appendix(CD-ROM).zip:0.09MB

ECUME ($$underline{E}$$ffective $$underline{C}$$hemistry database of fission products $$underline{U}$$nder $$underline{M}$$ultiphase r$$underline{E}$$action) is the database for the analyses of FP chemistry which strongly affects all the FP behaviors in a severe accident (SA) of nuclear facility like LWR. ECUME consists of three kinds of datasets: CRK (dataset for $$underline{C}$$hemical $$underline{R}$$eaction $$underline{K}$$inetics), EM ($$underline{E}$$lemental $$underline{M}$$odel set) and TD ($$underline{T}$$hermo$$underline{D}$$ynamic dataset). The present version of ECUME is prepared especially for the more accurate evaluation of cesium and iodine distribution in a reactor and release amount into an environment which should be of crucial importance towards the decommissioning of Fukushima Daiichi Nuclear Power Station of Tokyo Electric Power Company Holdings (1F) and the enhancement of LWR safety after the 1F SA.

Journal Articles

Refinement of source term and atmospheric dispersion simulations of radionuclides during the Fukushima Daiichi Nuclear Power Station accident

Terada, Hiroaki; Nagai, Haruyasu; Tsuzuki, Katsunori; Furuno, Akiko; Kadowaki, Masanao; Kakefuda, Toyokazu*

Journal of Environmental Radioactivity, 213, p.106104_1 - 106104_13, 2020/03

 Times Cited Count:0 Percentile:100(Environmental Sciences)

In order to assess the radiological dose to the public resulting from the Fukushima Daiichi Nuclear Power Station accident in Japan, the spatial and temporal distribution of radioactive materials in the environment is necessary to be reconstructed by computer simulations with the atmospheric transport, dispersion and deposition model (ATDM) and source term of radioactive materials discharged into the atmosphere is essential. In this study, we carried out refinement of the source term and improvement of ATDM simulation by using an optimization method based on Bayesian inference with various measurements (air concentration, surface deposition, and fallout). We also constructed the spatiotemporal distribution of some major radionuclides in the air and on the surface (optimized dispersion database) by using the optimized release rates and ATDM simulations which is used for the comprehensive dose assessment by coupling with the behavioral pattern of evacuees from the accident.

4109 (Records 1-20 displayed on this page)