Study on rational treatment/disposal of contaminated concrete waste considering leaching alteration (Contract research); FY2022 Nuclear Energy Science & Technology and Human Resource Development Project

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.

Estimation of the in-depth debris status of Fukushima Unit-2 and Unit-3 with Multi-physics modeling (Contract research); FY2021 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Waseda University*

JAEA-Review 2022-054, 150 Pages, 2023/02

JAEA-Review-2022-054.pdf:7.26MB

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. (hereafter referred to "1F"). 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 "Estimation of the in-depth debris status of Fukushima Unit-2 and Unit-3 with multi-physics modeling" conducted from FY2019 to FY2021. Since the final year of this proposal was FY2021, the results for three fiscal years were summarized. Continuous update on understanding of the damaged 1F reactors is important for safe and efficient decommissioning of the reactors. This study aimed to estimate the in-depth debris status of the damaged 1F Unit-2 and Unit-3 through multi-physics modeling, which comprises of MPS method, simulated molten debris relocation experiment and high-temperature melt property data acquisition in the three-year project from FY2019.

Third international challenge to model the medium- to long-range transport of radioxenon to four Comprehensive Nuclear-Test-Ban Treaty monitoring stations

Maurer, C.*; Galmarini, S.*; Solazzo, E.*; Kumierczyk-Michulec, J.*; Bar, J.*; Kalinowski, M.*; Schoeppner, M.*; Bourgouin, P.*; Crawford, A.*; Stein, A.*; et al.

Journal of Environmental Radioactivity, 255, p.106968_1 - 106968_27, 2022/12

https://doi.org/10.1016/j.jenvrad.2022.106968

After performing multi-model exercises in 2015 and 2016, a comprehensive Xe-133 atmospheric transport modeling challenge was organized in 2019. For evaluation measured samples for the same time frame were gathered from four International Monitoring System stations located in Europe and North America with overall considerable influence of IRE and/or CNL emissions. As a lesion learnt from the 2nd ATM-Challenge participants were prompted to work with controlled and harmonized model set ups to make runs more comparable, but also to increase diversity. Effects of transport errors, not properly characterized remaining emitters and long IMS sampling times (12 to 24 hours) undoubtedly interfere with the effect of high-quality IRE and CNL stack data. An ensemble based on a few arbitrary submissions is good enough to forecast the Xe-133 background at the stations investigated. The effective ensemble size is below five.

Assessment report of research on development activities in FY 2021 Activity; "Computational Science and Technology Research" (Result and in-advance evaluation)

Center for Computational Science & e-Systems

JAEA-Evaluation 2022-003, 61 Pages, 2022/11

JAEA-Evaluation-2022-003.pdf:1.42MB
JAEA-Evaluation-2022-003-appendix(CD-ROM).zip:6.16MB

Japan Atomic Energy Agency (hereinafter referred to as "JAEA") consults an assessment committee, "Evaluation Committee of Research Activities for Computational Science and Technology Research" (hereinafter referred to as "Committee") for result and in-advance evaluation of "Computational Science and Technology Research", in accordance with "General Guideline for the Evaluation of Government Research and Development (R&D) Activities" by Cabinet Office, Government of Japan, "Guideline for Evaluation of R&D in Ministry of Education, Culture, Sports, Science and Technology" and "Regulation on Conduct for Evaluation of R&D Activities" by the JAEA. In response to the JAEA's request, the Committee assessed the research program of the Center for Computational Science and e-Systems (hereinafter referred to as "CCSE"). The Committee evaluated the management and research activities of the CCSE based on explanatory documents prepared by the CCSE, and oral presentations with questions-and answers.

Development of the simplified boiling model applied to the large-scale detailed simulation

Ono, Ayako; Yamashita, Susumu; Sakashita, Hiroto*; Suzuki, Takayuki*; Yoshida, Hiroyuki

Proceedings of 13th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics, Operation and Safety (NUTHOS-13) (Internet), 12 Pages, 2022/09

Japan Atomic Energy Agency is developing the computational fluid dynamics code, JUPITER, based on the volume of fluid (VOF) method to analyze detailed thermal-hydraulics in a reactor. The detailed numerical simulation of boiling from a heating surface needs a substantial computational cost to resolve the microscale thermal-hydraulic phenomena such as the bubble generation from a cavity and evaporation of a micro-layer. This study developed the simplified boiling model from the heating surface to reduce the computational cost, which will apply to the detailed simulation code based on the surface tracking method such as JUPITER. We applied the simplified boiling model to JUPITER, and compared the simulation results with the experimental data of the vertical heating surface in the forced convection. We confirmed the degree of their reproducibility, and the issues to be modified were extracted.

Proposal and application of ROM-Lasso method for sensitivity coefficient evaluation

Katano, Ryota; Yamamoto, Akio*; Endo, Tomohiro*

Proceedings of International Conference on Physics of Reactors 2022 (PHYSOR 2022) (Internet), p.2032 - 2041, 2022/05

https://doi.org/10.13182/PHYSOR22-37557

We have proposed the ROM-Lasso method to perform an efficient evaluation of the sensitivity coefficients of ADS core parameters to cross sections without major modification of the core analysis system. In the ROM-Lasso method, the sensitivity coefficient vector is expanded via the subspace bases so-called Active Subspace (AS), and the effective number of unknowns is reduced. Then, the expansion coefficients are determined via the penalized linear regression with the core parameters obtained by the random sampling, and the sensitivity coefficient vector is estimated. Owing to the AS, the required number of the core calculations is dramatically reduced in the ROM-Lasso method. In this work, we take the sensitivity coefficient evaluation of the coolant void reactivity at the end of the cycle for example and demonstrate how estimation accuracy depends on the number of samples and the AS.

Review of research on Advanced Computational Science in FY2020

Center for Computational Science & e-Systems

JAEA-Evaluation 2021-001, 66 Pages, 2021/11

JAEA-Evaluation-2021-001.pdf:1.66MB

Research on advanced computational science for nuclear applications, based on "the plan to achieve the mid- and long-term goal of the Japan Atomic Energy Agency", has been performed by Center for Computational Science & e-Systems (CCSE), Japan Atomic Energy Agency. CCSE established a committee consisting of external experts and authorities which does research evaluation and advice for the assistance of the future research and development. This report summarizes the results of the R&D performed by CCSE in FY2020 (April 1st, 2020 - March 31st, 2021), the results expected at the end of the 3rd mid and long-term goal period, and the evaluation by the committee on them.

Estimation of the in-depth debris status of Fukushima Unit-2 and Unit-3 with Multi-physics modeling (Contract research); FY2019 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Waseda University*

JAEA-Review 2020-035, 102 Pages, 2021/01

JAEA-Review-2020-035.pdf:6.82MB

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 FY2019. 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 FY2019, this report summarizes the research results of the "Estimation of the In-Depth Debris Status of Fukushima Unit-2 and Unit-3 with Multi-Physics Modeling". Continuous update on understanding of the damaged Fukushima reactors is important for safe and efficient decommissioning of the reactors. This study aims to estimate the in-depth debris status of the damaged Fukushima Unit-2 and Unit-3 through multi-physics modeling, which comprises of MPS method, simulated molten debris relocation experiment and high-temperature melt property data acquision in the three-year project from FY2019.

Review of research on Advanced Computational Science in FY2019

Center for Computational Science & e-Systems

JAEA-Evaluation 2020-002, 37 Pages, 2020/12

JAEA-Evaluation-2020-002.pdf:1.59MB

Research on advanced computational science for nuclear applications, based on "the plan to achieve the mid and long term goal of the Japan Atomic Energy Agency", has been performed at Center for Computational Science & e-Systems (CCSE), Japan Atomic Energy Agency. CCSE established a committee consisting of outside experts and authorities which does research evaluation and advice for the assistance of the future research and development. This report summarizes the results of the R&D performed at CCSE in FY2019 (April 1st, 2019 - March 31st, 2020) and the evaluation by the committee on them.

Characterizing vertical migration of Cs in organic layer and mineral soil in Japanese forests; Four-year observation and model analysis

Muto, Kotomi; Atarashi-Andoh, Mariko; Matsunaga, Takeshi*; Koarashi, Jun

Journal of Environmental Radioactivity, 208-209, p.106040_1 - 106040_10, 2019/11

https://doi.org/10.1016/j.jenvrad.2019.106040

Vertical distributions of Cs in the soil profile were observed at five forest sites with different vegetation types for 4.4 years after the Fukushima Dai-ichi Nuclear Power Plant accident, and Cs migration in the organic layer and mineral soil was analyzed based on a comparison of models and observations. Cesium-137 migration from the organic layer was faster than that observed in European forests, suggesting that the mobility and bioavailability of Cs could be suppressed rapidly in Japanese forests. The diffusion coefficients of Cs in the mineral soil were estimated to be 0.042-0.55 cmy, which were roughly comparable with those of European forest soils affected by the Chernobyl Nuclear Power Plant accident. Model predictions indicated Cs mainly distributed in the surface mineral soil at 10 years after the accident. It suggest that the Cs deposited onto Japanese forest ecosystems will be retained in the surface layers of mineral soil for a long time.