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Collaborative Laboratories for Advanced Decommissioning Science; Hokkaido University*
JAEA-Review 2023-027, 126 Pages, 2024/03
JAEA-Review-2023-027.pdf:5.51MB
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 "Study on rational treatment/disposal of contaminated concrete waste considering leaching alteration" conducted from FY2020 to FY2022. The present study aims to understand migration behaviors of radionuclides in relation to the properties of concrete altered by leaching, to develop migration model of radionuclides, and to evaluate waste management scenarios, focusing on underground concrete structures in contact with contaminated water.
Kato, Tomoaki; Yamagishi, Isao
JAEA-Technology 2023-018, 53 Pages, 2023/11
JAEA-Technology-2023-018.pdf:2.6MB
In the decommissioning of Fukushima Daiichi Nuclear Power Station, radioactive carbonate slurry waste was generated using the Advanced Liquid Processing System (ALPS) pretreatment and temporarily stored in a high integrity container (HIC). In 2015, overflow of supernatant from HIC estimate as bubble retention in the carbonate slurry was discovered, increasing the need for a safety assessment of the carbonate slurry stored the HIC (HIC slurry). In this study, a carbonate slurry (simulated slurry) was prepared according to the Mg/Ca mass ratio in the ALPS inlet water of the HIC slurry which overflew the HIC. The effects of reaction time during the pretreatment process, suspended solids concentration (SS concentration), and settling time on the particle composition, morphology and rheological properties of the slurry were investigated. Evaluating the effect of reaction time and concentration process on chemical properties in slurry production, the effect of the reaction time was not confirmed in the simulated slurry that had undergone the concentration process, and slurry prepared at SS concentration of 150 g/L was composed of formless particles have a particle diameter of 0.4 
m or less. We also investigate the effect of SS concentration on sedimentability, decrease in SS concentration by dilution with processing solution contributed to an increase in the initial slurry settling velocity. Furthermore, two different flow characteristics were observed depending on the settling time, suggesting that the slurry at the initial settling time has non-Bingham flow properties, whereas it changes to Bingham flow properties as the settling time becomes longer. In addition, yield stress was increased with settling time, and this yield stress was found to be exponentially proportional to the density of the slurry. These results provide knowledge to estimate the current state of HIC slurry and are expected to contribute to the safety assessment.
Takeda, Takeshi
JAEA-Data/Code 2023-012, 75 Pages, 2023/10
JAEA-Data-Code-2023-012.pdf:4.45MB
An experiment denoted as TR-LF-15 was conducted on June 11, 2014 using the Large Scale Test Facility (LSTF) in the Rig of Safety Assessment-V (ROSA-V) Program. The ROSA/LSTF experiment TR-LF-15 simulated accident management (AM) actions during a station blackout transient with TMLB' scenario with pump seal loss-of-coolant accident (LOCA) in a pressurized water reactor (PWR). This scenario is featured by loss of auxiliary feedwater functions. The pump seal LOCA was simulated by a 0.1% cold leg break. The test assumptions included total failure of both high pressure injection system and low pressure injection system of emergency core cooling system (ECCS). Also, it was presumed non-condensable gas (nitrogen gas) inflow to the primary system from accumulator (ACC) tanks of ECCS. When steam generator (SG) secondary-side collapsed liquid level dropped to a certain low liquid level, the primary pressure turned to rise. After the SG secondary-side became voided, the safety valve of a pressurizer cyclically opened which led to loss of primary coolant. Core uncovery thus took place owing to core boil-off at high pressure. When an increase of 10 K was confirmed in cladding surface temperature of simulated fuel rods, SG secondary-side depressurization was started as the first AM action. At that time, the safety valves in both SGs were fully opened. Primary depressurization was initiated by completely opening the pressurizer safety valve as the second AM action with some delay after the first AM action onset. When the SG secondary-side pressure lowered to 1.0 MPa following the first AM action, water was injected into the secondary-side of both SGs via feedwater lines with low-head pumps as the third AM action. A reduction in the primary pressure was accelerated because the heat removal from the SG secondary-side system resumed shortly after the third AM action initiation.
Collaborative Laboratories for Advanced Decommissioning Science; Hitachi-GE Nuclear Energy*
JAEA-Review 2022-058, 191 Pages, 2023/02
JAEA-Review-2022-058.pdf:16.99MB
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 (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 FY2019, this report summarizes the research results of the "Fluorination method for classification of the waste generated by fuel debris removal" conducted from FY2019 to FY2021. Since the final year of this proposal was FY2021, the results for three fiscal years were summarized. The present study aims to develop a method for separating nuclear fuel material from waste by fluorination in order to contribute to the classification of waste generated by fuel debris removal at 1F. In order to comprehensively evaluate the fluorination behavior for the generated phase in various MCCI products, some simulated wastes were prepared by controlling redox conditions, and the fluorination experiment was carried out.
Collaborative Laboratories for Advanced Decommissioning Science; Hokkaido University*
JAEA-Review 2022-038, 102 Pages, 2023/01
JAEA-Review-2022-038.pdf:4.76MB
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 FY2020, this report summarizes the research results of the "Study on rational treatment/disposal of contaminated concrete waste considering leaching alteration" conducted in FY2021. The present study aims to understand migration behaviors of radionuclides in relation to the properties of concrete altered by leaching, to develop a model to predict concentration profiles, and to analyze waste management scenarios, with a focus on underground concrete structures in contact with contaminated water. Migration behaviors depend on radionuclides and their chemical species. Sorption of I
is less significant on C-S-H and C-A-S-H than on hardened cement paste with two orders of magnitude smaller distribution coefficient 
, while of U was the same …
Li, C.-Y.; Watanabe, Akira*; Uchibori, Akihiro; Okano, Yasushi
Journal of Nuclear Science and Technology, 23 Pages, 2023/00
Times Cited Count：1 Percentile：72.91(Nuclear Science & Technology)Collaborative Laboratories for Advanced Decommissioning Science; Hitachi-GE Nuclear Energy*
JAEA-Review 2022-003, 126 Pages, 2022/06
JAEA-Review-2022-003.pdf:8.01MB
JAEA/CLADS had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project. Among the adopted proposals in FY2019, this report summarizes the research results of the "Fluorination Method for Classification of the Waste Generated by Fuel Debris Removal" conducted in FY2020.
Collaborative Laboratories for Advanced Decommissioning Science; Hokkaido University*
JAEA-Review 2021-070, 98 Pages, 2022/03
JAEA-Review-2021-070.pdf:4.75MB
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 FY2020. 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 "Study on rational treatment/disposal of contaminated concrete waste considering leaching alteration" conducted in FY2020. The present study aims to understand migration behaviors of radionuclides in relation to the properties of concrete materials altered due to leaching, to develop a model to simulate the migration behaviors based on the experimental findings, and to analyze waste management scenarios for radioactive concrete. The focus of the study is the underground concrete structures of Fukushima Daiichi Nuclear Power Station, which is in contact with contaminated water.
Takeda, Takeshi
JAEA-Data/Code 2021-006, 61 Pages, 2021/04
JAEA-Data-Code-2021-006.pdf:2.78MB
An experiment denoted as SB-PV-09 was conducted on November 17, 2005 using the Large Scale Test Facility (LSTF) in the Rig of Safety Assessment-V (ROSA-V) Program. The ROSA/LSTF experiment SB-PV-09 simulated a 1.9% pressure vessel top small-break loss-of-coolant accident in a pressurized water reactor (PWR). The test assumptions included total failure of high pressure injection system and non-condensable gas (nitrogen gas) inflow to the primary system from accumulator (ACC) tanks of emergency core cooling system (ECCS). In the experiment, liquid level in the upper-head was found to control break flow rate. When maximum core exit temperature reached 623 K, steam generator (SG) secondary-side depressurization was initiated by fully opening the relief valves in both SGs as an accident management (AM) action. The AM action, however, was ineffective on the primary depressurization until the SG secondary-side pressure decreased to the primary pressure. Meanwhile, the core power was automatically reduced when maximum cladding surface temperature of simulated fuel rods exceeded the pre-determined value of 958 K to protect the LSTF core due to late and slow response of core exit temperature. After the automatic core power reduction, loop seal clearing (LSC) was induced in both loops by steam condensation on the ACC coolant injected into cold legs. The whole core was quenched because of core recovery after the LSC. After the ACC tanks started to discharge nitrogen gas, the pressure difference between the primary and SG secondary sides became larger. After the continuous core cooling was confirmed through the actuation of low pressure injection system of ECCS, the experiment was terminated. This report summarizes the test procedures, conditions, and major observations in the ROSA/LSTF experiment SB-PV-09.
Collaborative Laboratories for Advanced Decommissioning Science; Hitachi-GE Nuclear Energy*
JAEA-Review 2020-034, 155 Pages, 2021/01
JAEA-Review-2020-034.pdf:10.77MB
JAEA/CLADS had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project in FY2019. Among the adopted proposals in FY2019, this report summarizes the research results of the "Fluorination Method for Classification of the Waste Generated by Fuel Debris Removal" conducted in FY2019.
Task Force on Research Strategy for Debris of Fukushima Daiichi Nuclear Power Station
JAEA-Review 2020-055, 171 Pages, 2020/12
JAEA-Review-2020-055.pdf:5.66MB
Design, planning and control of debris-related processes, namely retrieval, storage management, processing and disposal of the debris, are required for the safe and steady decommissioning of Fukushima Daiichi Nuclear Power Station (1F). Status inside primary containment vessel of 1F must be known by the PCV investigation and fuel debris sample analysis. Continuous updating and improvement of the process design are important through ascertainment of the cause of the accident. The roadmap for the 1F decommissioning have shown the milestone of commencement of trial retrieval of fuels debris within 2021, which indicates the analysis of fuel debris sample begin in earnest. This report recommends required debris analysis in relation with issues for the retrieval, storage management, processing and disposal, and ascertainment of the cause of the 1F accident. Practical analysis plan is expected to be prepared based on this report.
Herranz, L. E.*; Jacquemain, D.*; Nitheanandan, T.*; Sandberg, N.*; Barr
, F.*; Bechta, S.*; Choi, K.-Y.*; D'Auria, F.*; Lee, R.*; Nakamura, Hideo
Progress in Nuclear Energy, 127, p.103432_1 - 103432_14, 2020/09
Times Cited Count：3 Percentile：11.26(Nuclear Science & Technology)Task Force on Research Strategy for Debris of Fukushima Daiichi Nuclear Power Station
JAEA-Review 2020-004, 140 Pages, 2020/05
JAEA-Review-2020-004.pdf:4.22MB
Design, planning and control of debris-related processes, namely retrieval, storage management, processing and disposal of the debris, are required for the safe and steady decommissioning of Fukushima Daiichi Nuclear Power Station (1F). Status inside primary containment vessel of 1F must be known by the PCV investigation and fuel debris sample analysis. Continuous updating and improvement of the process design are important through ascertainment of the cause of the accident. The roadmap for the 1F decommissioning have shown the milestone of commencement of trial retrieval of fuels debris within 2021, which indicates the analysis of fuel debris sample begin in earnest. This report recommends required debris analysis in relation with issues for the retrieval, storage management, processing and disposal, and ascertainment of the cause of the 1F accident. Practical analysis plan is expected to be prepared based on this report.
Oba, Takashi*; Ishikawa, Tetsuo*; Nagai, Haruyasu; Tokonami, Shinji*; Hasegawa, Arifumi*; Suzuki, Gen*
Scientific Reports (Internet), 10(1), p.3639_1 - 3639_11, 2020/02
Times Cited Count：18 Percentile：83.61(Multidisciplinary Sciences)Internal doses of residents after the Fukushima Daiichi Nuclear Power Station accident have been reconstructed. In total 896 behaviour records in the Fukushima Health Management Survey were analysed to estimate thyroid doses via inhalation, using a spatiotemporal radionuclides concentration database constructed by atmospheric dispersion simulations. After a decontamination factor for sheltering and a modifying factor for the dose coefficient were applied, estimated thyroid doses were close to those estimated on the basis of direct thyroid measurement. The median and 95th percentile of thyroid doses of 1-year-old children ranged from 1.2 to 15 mSv and from 7.5 to 30 mSv, respectively.
Yoshizawa, Atsufumi*; Oba, Kyoko; Kitamura, Masaharu*
Nihon Genshiryoku Gakkai Wabun Rombunshi, 18(2), p.55 - 68, 2019/06
This study aims to improve the potential of an emergency response by analyzing the workload management during the accident at the Emergency Response Center (ERC) of TEPCO's Fukushima Daiichi Nuclear Power Plant. Specifically, the research focused on the response of the ERC during the time between the discontinuation of Unit 3 core water injection and its recovery. It identified the different types of workload at the ERC had and how they had been managed based on the record of a TV conference. It also deduced the casual factors of the responses, supplementing the interview record of the director of ERC at the time by applying workload management analysis. On the basis of these findings, lessons to enhance the potential of the on-site emergency response have been obtained for ERC and outside organizations.
Okuno, Hiroshi; Okamoto, Akiko; Ebine, Noriya; Hayakawa, Tsuyoshi; Tanaka, Tadao
Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 15 Pages, 2019/05
In the event of a nuclear or radiological emergency, the Japan Atomic Energy Agency (JAEA) as a designated public corporation assigned in the Disaster Countermeasures Basic Act of Japan undertakes a role to support the national government and local governments. This paper (1) illuminates the roles of the JAEA as a designated public corporation for preparedness and response to a nuclear or radiological emergency of nuclear facilities; (2) summarizes emergency response activities of the JAEA in accordance with its Disaster Management Operation Plan against the off-site radiological emergencies attributed to a loss of control of the Tokyo Electric Power Company (TEPCO)'s Fukushima Daiichi Nuclear Power Station that occurred in 2011; and (3) reports its activities in normal times especially participation in the drills organized by the national government and local governments in the light of the Basic Disaster Management Plan of Japan and Local Disaster Management Plans of prefectural governments, respectively.
Suzuki, Minoru*; Sakai, Takaaki*; Takata, Takashi; Doda, Norihiro
Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 7 Pages, 2019/05
With an aim to establish a quantitative risk assessment of accident managements (AMs) for various external hazards, the plant dynamics analyses with Continuous Markov Chain Monte Carlo (CMMC) method were carried out to assess repeatedly occurred multi-failures by volcano ash in volcanic eruption event. AM repetition of the filter exchange to recover the cooling function of the air coolers were considered. The results showed that this method can evaluate the effectiveness of AM measures against volcanic ash fall events with respect to time progress.
Saegusa, Jun; Koma, Yoshikazu; Ashida, Takashi
JAEA-Review 2018-017, 259 Pages, 2018/12
JAEA-Review-2018-017.pdf:53.88MB
Collaborative Laboratories for Advanced Decommissioning Science (CLADS) is responsible to promote international cooperation in the R&D activities on the decommissioning of Fukushima Daiichi Nuclear Power Station and to develop the necessary human resources. CLADS held the Fukushima Research Conference on Development of Analytical Techniques in Waste Management (FRCWM 2018) on 19th and 20th June, 2018. This report compiles the abstracts and the presentation materials in the above conference.
Takeda, Takeshi
JAEA-Data/Code 2018-003, 60 Pages, 2018/03
JAEA-Data-Code-2018-003.pdf:3.68MB
Experiment SB-PV-07 was conducted on June 9, 2005 using LSTF. Experiment simulated 1% pressure vessel top small-break LOCA in PWR under total failure of HPI system and nitrogen gas inflow to primary system from ACC tanks. Liquid level in upper-head was found to control break flow rate. Coolant was started to manually inject from HPI system into cold legs as first accident management (AM) action when maximum core exit temperature reached 623 K. Fuel rod surface temperature largely increased because of late and slow response of core exit temperature. SG secondary-side depressurization was initiated by fully opening relief valves as second AM action when primary pressure decreased to 4 MPa. However, second AM action was not effective on primary depressurization until SG secondary-side pressure decreased to primary pressure. Pressure difference became larger between primary and SG secondary sides after ACC tanks started to discharge nitrogen gas.
Sugiyama, Daisuke*; Kimura, Hideo; Tachikawa, Hirokazu*; Iimoto, Takeshi*; Kawata, Yosuke*; Ogino, Haruyuki*; Okoshi, Minoru*
Journal of Radiological Protection, 38(1), p.456 - 462, 2018/03
Times Cited Count：0 Percentile：0.01(Environmental Sciences)Experience after the accident at the Fukushima Daiichi Nuclear Power Station has shown that there is a need to establish radiation protection criteria for radioactive waste management consistent with the criteria adopted for the remediation of existing exposure situations. A stepwise approach to setting such criteria is proposed. Initially, a reference level for annual effective dose from waste management activities in the range 1-10 mSv should be set, with the reference level being less than the reference level for ambient dose. Subsequently, the reference level for annual effective dose from waste management activities should be reduced in one or more steps to achieve a final target value of 1 mSv. The dose criteria at each stage should be determined with relevant stakeholder involvement. Illustrative case studies show how this stepwise approach might be applied in practice.
