Study on degradation of fuel debris by combined effects of radiological, chemical, and biological functions (Contract research); FY2021 Nuclear Energy Science & Technology and Human Resource Development Project

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

JAEA-Review 2022-066, 91 Pages, 2023/03

JAEA-Review-2022-066.pdf:5.88MB

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 FY2019, this report summarizes the research results of the "Study on degradation of fuel debris by combined effects of radiological, chemical, and biological functions" conducted in FY2021. In the project, radiochemists, nuclear chemists, nuclear physicists, material scientists, and environmental biologists are teamed to elucidate the mechanism of the degradation of fuel debris by combined effects of radiological, chemical, and biological functions. In fiscal year 2021, the members of the project team have conducted on the microbial degradation of the simulated fuel debris under -ray irradiation, complex formation of pentavalent uranium, construction of microchannel system to detect micro-particles and the simulated fuel debris, sorption of tetravalent elements

Pore connectivity influences mass transport in natural rocks; Pore structure, gas diffusion and batch sorption studies

Yuan, X.*; Hu, Q.*; Lin, X.*; Zhao, C.*; Wang, Q.*; Tachi, Yukio; Fukatsu, Yuta; Hamamoto, Shoichiro*; Siitari-Kauppi, M.*; Li, X.*

Journal of Hydrology, 618, p.129172_1 - 129172_15, 2023/03

https://doi.org/10.1016/j.jhydrol.2023.129172

Horonobe Underground Research Laboratory Project; Investigation program for the 2022 fiscal year

Nakayama, Masashi

JAEA-Review 2022-026, 66 Pages, 2022/11

JAEA-Review-2022-026.pdf:12.31MB

The Horonobe Underground Research Laboratory (URL) Project is being pursued by the Japan Atomic Energy Agency (JAEA) to enhance the reliability of relevant disposal technologies for geological disposal of High-level Radioactive Waste through investigations of the deep geological environment within the host sedimentary rock at Horonobe Town in Hokkaido, north Japan. In fiscal year 2022, we continue to conduct research 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", which are the important issues shown in the Horonobe underground research plan from fiscal year 2020. The main studies to be conducted in fiscal year 2022 are as follows. As "Study on near-field system performance in geological environment", we will continue to the test under the simulated condition in which the heat generation by the high-level radioactive waste has subsides in the full-scale engineered barrier system (EBS) performance experiment. We will also conduct solute transport experiment with model testing that take into account the effects of organic matter, microbes, and colloids, and initiate borehole investigation to evaluate solute transport experiments on fractures distribute in Koetoi formation. As "Demonstration of repository design concept", we will continue experiment and analysis of concrete deterioration in the underground environment as a demonstration of remote technique for emplacement and retrievable. As a demonstration of the closure techniques, laboratory tests will be continued to investigate the mechanism of bentonite runoff behaviour, which could be a factor in changing the performance of backfill material, and to expand data on swelling and deformation behaviour. In addition, in-situ borehole closure tests will be conducted to evaluate the applicability of the closure method. As "Understanding of buffering behaviour of

Clogging properties of HEPA filter induced by loading of soot from burned glove-box panel materials

Tashiro, Shinsuke; Ono, Takuya; Amano, Yuki; Yoshida, Ryoichiro; Watanabe, Koji*; Abe, Hitoshi

Nuclear Technology, 208(10), p.1553 - 1561, 2022/10

https://doi.org/10.1080/00295450.2022.2045179

To contribute to the confinement safety evaluation of the radioactive materials in the Glove box (GB) fire accident, combustion tests with the Polymethyl methacrylate (PMMA) and the Polycarbonate (PC) as typical panel materials for the GB have been conducted with a relatively large scale apparatus. As the important data for evaluating confinement safety, the release ratio and the particle size distribution of the soot generated from the burned materials were obtained. Furthermore, the rise of the differential pressure (P) of the high efficiency particle air (HEPA) filter by the soot loading was also investigated. As results, the release ratio of the soot from the PC was about seven times as large as the PMMA. In addition, it was found that the behavior of the rise of the P with soot loading could be represented uniformly regardless of kinds of combustion materials by considering effect of the loading volume of the soot particle in the relatively low loading region.

Development of dynamic PRA methodology for external hazards (Application of CMMC method to severe accident analysis code)

Li, C.-Y.; Watanabe, Akira*; Uchibori, Akihiro; Okano, Yasushi

Dai-26-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu (Internet), 4 Pages, 2022/07

https://doi.org/10.1299/jsmepes.2022.26.A234

Identifying accident scenarios that could lead to severe accidents and evaluating their frequency of occurrence are essential issues. This study aims to establish the methodology of the dynamic Probabilistic Risk Assessment (PRA) for sodium-cooled fast reactors that can consider the time dependency and the interdependence of each event. Specifically, the Continuous Markov chain Monte Carlo (CMMC) method is newly applied to the SPECTRA code, which analyzes the severe accident conditions of nuclear reactors, to develop an evaluation methodology for typical external hazards. Currently, a fault-tree model of air coolers of decay heat removal system is implemented as the CMMC method, and a series of preliminary analysis of the plant's transient characteristics under the scenario of volcanic ashfall has been conducted.

Development of the sintering solidification method for spent zeolite to long-term stabilization (Contract research); FY2020 Nuclear Energy Science & Technology and Human Resource Development Project

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

JAEA-Review 2022-008, 116 Pages, 2022/06

JAEA-Review-2022-008.pdf:5.36MB

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 FY2018, this report summarizes the research results of the "Development of the sintering solidification method for spent zeolite to long-term stabilization" conducted from FY2018 to FY2021 (this contract was extended to FY2021). Since the final year of this proposal was FY2021, the results for four fiscal years were summarized. The present study aims to develop a new sintering solidification method in which glass is added as a binder to spent zeolite which is adsorbed radionuclides such as Cs and the nuclides are immobilized by sintering them. In this project, the optimum conditions for sintering solidification and the basic performance of the sintered solidified body will be evaluated by cold tests, and they will be demonstrated by hot tests. In FY2020, the cold tests

Current status of Geological disposal by "all-Japan" activities, 6; Post-closure safety assessment (2)

Tachi, Yukio; Saito, Takumi*; Kirishima, Akira*

Nihon Genshiryoku Gakkai-Shi ATOMO, 64(5), p.290 - 295, 2022/05

https://doi.org/10.3327/jaesjb.64.5_290

no abstracts in English

Development of JAEA sorption database (JAEA-SDB); Update of sorption/QA data in FY2021

Sugiura, Yuki; Suyama, Tadahiro*; Tachi, Yukio

JAEA-Data/Code 2021-017, 58 Pages, 2022/03

JAEA-Data-Code-2021-017.pdf:1.98MB

Sorption behavior of radionuclides (RNs) in buffer materials (bentonites), rocks and cementitious materials is one of the key processes in a safe geological disposal of radioactive waste because RNs migration in these materials is expected to be retarded by the sorption process. Therefore, it is necessary to understand the sorption process and develop a database compiling reliable data and mechanistic/predictive models so that reliable parameters can be set under a variety of geochemical conditions relevant to a performance assessment (PA). For this purpose, Japan Atomic Energy Agency (JAEA) has developed the database of sorption parameters in bentonites, rocks and cementitious materials. This sorption database (SDB) was firstly developed as an important basis for the H12 PA of a high-level radioactive waste disposal, and have been provided through the Web. JAEA has continued to improve and update the SDB in the view of potential future needs of data focusing on assuring the desired quality level and testing the usefulness of the databases for possible applications to the PA-related parameter setting. This report focuses on updating of the sorption database (JAEA-SDB) as a basis of integrated approach for the PA-related distribution coefficient (Kd) setting and development of mechanistic sorption models. This report also includes an overview of the database structure and contents. Kd data and their quality assurance (QA) results were updated from literature collected with wider ranges. As a result, 8,503 Kd data from 70 references related to the above-mentioned systems were added and the total number of Kd values in JAEA-SDB reached 79,072. The QA/classified Kd data reached about 75.4% for all Kd data in JAEA-SDB. The updated JAEA-SDB is expected to make it possible to give a basis for the next-step PA-related Kd setting.

Horonobe Underground Research Laboratory Project; Investigation report for the 2020 fiscal year

Nakayama, Masashi

JAEA-Review 2021-053, 133 Pages, 2022/02

JAEA-Review-2021-053.pdf:14.45MB

The Horonobe Underground Research Laboratory (URL) Project is being pursued by the Japan Atomic Energy Agency (JAEA). The main aim of this project is to enhance the reliability of relevant disposal technologies for geological disposal of high-level radioactive waste through a comprehensive research and development (R&D) program in the deep geological environment within the host sedimentary rock at Horonobe in Hokkaido, north Japan. In fiscal year 2020, JAEA continued R&D on three important issues specified in the "Horonobe Underground Research Plan from Fiscal Year 2020", which involve "Study on nearfield system performance in geological environment", "Demonstration of repository design options", and "Understanding of buffering behavior of sedimentary rock to natural perturbations". Specifically, 'full scale engineered barrier system (EBS) experiment' and 'solute transport experiment' were carried out as part of "Study on near-field system performance in geological environment". 'Development and testing of EBS emplacement / retrieval and tunnel closure technologies' and 'evaluation of EBS behavior over 100C' were addressed for "Demonstration of repository design options". A study on "Understanding of buffering behavior of sedimentary rock to natural perturbations" was also implemented in two areas, 'evaluation of hydromechanical responses of faults to water pressure changes' and 'development of techniques for evaluating self-sealing behavior of an excavation damaged zone after backfilling'. The results of the R&D, along with those obtained in other departments of JAEA, will reinforce the technical basis for both repository implementation and safety regulation. For the sake of this, JAEA will steadily proceed with this project in collaboration with relevant organizations and universities both domestically and internationally and also widely publish the plans and results of the R&D to ensure their transparency and technical reliability.

Impact of MOX fuel use in light-water reactors; Long-term radiological consequences of disposal of high-level waste in a geological repository

Minari, Eriko*; Kabasawa, Satsuki; Mihara, Morihiro; Makino, Hitoshi; Asano, Hidekazu*; Nakase, Masahiko*; Takeshita, Kenji*

Journal of Nuclear Science and Technology, 11 Pages, 2022/00

https://doi.org/10.1080/00223131.2022.2146016