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Ikeuchi, Hirotomo; Koyama, Shinichi
Nihon Genshiryoku Gakkai-Shi ATOMO
, 66(2), p.74 - 78, 2024/02
For the steady removal of fuel debris from the TEPCO's Fukushima Daiichi Nuclear Power Station (1F), it is an urgent issue to establish analysis technology and systems for fuel debris samples with unknown properties (unknown samples). For this purpose, through analysis tests using samples with known properties (simulated fuel debris) and discussions among experts, the validity of analysis results and the factors that cause errors has been identified. In addition to knowing the current level of analysis accuracy, studies are being conducted to understand and improve the influencing factors. This paper introduces a part of the development of infrastructure for analysis and evaluation technology of "nuclides and element content."
Ikeuchi, Hirotomo; Sasaki, Shinji; Onishi, Takashi; Nakayoshi, Akira; Arai, Yoichi; Sato, Takumi; Ohgi, Hiroshi; Sekio, Yoshihiro; Yamaguchi, Yukako; Morishita, Kazuki; et al.
JAEA-Data/Code 2023-005, 418 Pages, 2023/12
JAEA-Data-Code-2023-005-01.pdf:24.59MBJAEA-Data-Code-2023-005-02.pdf:32.18MB
For safe and steady decommissioning of Tokyo Electric Power Company Holdings' Fukushima Daiichi Nuclear Power Station (1F), information concerning composition and physical/chemical properties of fuel debris generated in the reactors should be estimated and provided to other projects conducting the decommissioning work including the retrieval of fuel debris and the subsequent storage. For this purpose, in FY2021, samples of contaminants (the wiped smear samples and the deposits) obtained through the internal investigation of the 1F Unit 2 were analyzed to clarify the components and to characterize the micro-particles containing uranium originated from fuel (U-bearing particles) in detail. This report summarized the results of analyses performed in FY2021, including the microscopic analysis by SEM and TEM, radiation analysis, and elemental analysis by ICP-MS, as a database for evaluating the main features of each sample and the probable formation mechanism of the U-bearing particles.
Koyama, Shinichi; Ikeuchi, Hirotomo; Mitsugi, Takeshi; Maeda, Koji; Sasaki, Shinji; Onishi, Takashi; Tsai, T.-H.; Takano, Masahide; Fukaya, Hiroyuki; Nakamura, Satoshi; et al.
Hairo, Osensui, Shorisui Taisaku Jigyo Jimukyoku Homu Peji (Internet), 216 Pages, 2023/11
In FY 2021 and 2022, JAEA perfomed the subsidy program for "the Project of Decommissioning and Contaminated Water Management (Development of Analysis and Estimation Technology for Characterization of Fuel Debris (Development of Technologies for Enhanced Analysis Accuracy, Thermal Bahavior Estimation, and Simplified Analysis of Fuel Debris)" started in FY 2021. This presentation material summarized the results of the project, which will be available shortly on the website of Management Office for the Project of Decommissioning, Contaminated Water and Treated Water Management.
Ikeuchi, Hirotomo; Koyama, Shinichi; Osaka, Masahiko; Takano, Masahide; Nakamura, Satoshi; Onozawa, Atsushi; Sasaki, Shinji; Onishi, Takashi; Maeda, Koji; Kirishima, Akira*; et al.
JAEA-Technology 2022-021, 224 Pages, 2022/10
JAEA-Technology-2022-021.pdf:12.32MB
A set of technology, including acid dissolving, has to be established for the analysis of content of elements/nuclides in the fuel debris samples. In this project, a blind test was performed for the purpose of clarifying the current level of analytical accuracy and establishing the alternative methods in case that the insoluble residue remains. Overall composition of the simulated fuel debris (homogenized powder having a specific composition) were quantitatively determined in the four analytical institutions in Japan by using their own dissolving and analytical techniques. The merit and drawback for each technique were then evaluated, based on which a tentative flow of the analyses of fuel debris was constructed.
Kurata, Masaki; Okuzumi, Naoaki*; Nakayoshi, Akira; Ikeuchi, Hirotomo; Koyama, Shinichi
Journal of Nuclear Science and Technology, 59(7), p.807 - 834, 2022/07
Times Cited Count：14 Percentile：93.54(Nuclear Science & Technology)Immediately after the 1F-accident, various attempts have been made to evaluate the fuel debris characteristics toward the decommissioning of 1F. The present review outlines those attempts. In the years immediately following the 1F-accident, the knowledge obtained from the 1F-site (especially from the damaged reactors of Units 1, 2 and 3) was extremely limited. The approximate location of fuel debris was investigated by muon tomography, and its characteristics were roughly estimated based on the past findings such as the results of the Three Mile Island-II accident investigation in the United States, which gave us information of prototypical accident scenarios and debris characteristics for pressurized water reactor accident. After that, various internal investigation robots were developed, and from 2017, investigation of the inside of the reactor containment vessel was started using these robots. Consequently, these three units were found to have core damage status and debris distribution that were rather different from what had been expected based on the typical accident scenario of a pressurized water reactor. In parallel, a small amount of U-bearing particle was recovered from the smear samples of these robots. The analysis of these particles is ongoing to get information relevant to fuel debrsi body. Furthermore, international collaboration is ongoing mainly under OECD/NEA, including accident analysis and debris characterization. From now on, one need to further understand 1F-accident scenario and progress debris characterization based on these 1F-site information.
Ikeuchi, Hirotomo
Journal of Nuclear Science and Technology, 59(6), p.768 - 780, 2022/06
Times Cited Count：1 Percentile：18.18(Nuclear Science & Technology)Koyama, Shinichi; Nakagiri, Toshio; Osaka, Masahiko; Yoshida, Hiroyuki; Kurata, Masaki; Ikeuchi, Hirotomo; Maeda, Koji; Sasaki, Shinji; Onishi, Takashi; Takano, Masahide; et al.
Hairo, Osensui Taisaku jigyo jimukyoku Homu Peji (Internet), 144 Pages, 2021/08
JAEA performed the subsidy program for the "Project of Decommissioning and Contaminated Water Management (Development of Analysis and Estimation Technology for Characterization of Fuel Debris (Development of Technologies for Enhanced Analysis Accuracy and Thermal Behavior Estimation of Fuel Debris))" in 2020JFY. This presentation summarized briefly the results of the project, which will be available shortly on the website of Management Office for the Project of Decommissioning and Contaminated Water Management.
Ikeuchi, Hirotomo; Yano, Kimihiko; Washiya, Tadahiro
Journal of Nuclear Science and Technology, 57(6), p.704 - 718, 2020/06
Times Cited Count：6 Percentile：53.41(Nuclear Science & Technology)To suggest efficient process of the fuel debris treatment after the retrieval from the Fukushima Daiichi Nuclear Power Plant (1F), thorough investigation is indispensable on potential source of U in the fuel debris. Estimation on the fuel debris accumulated in the reactor pressure vessel is specifically important due to its limited accessibility. The present study aims to estimate the chemical forms of U in the in-vessel fuel debris, especially in the minor phases such as metallic phases, by performing the thermodynamic calculation considering the material relocation and changing environment during the accident progression in the 1F Unit 2. Input conditions for the thermodynamic calculation such as composition, temperature, and oxygen amount were assumed mainly based on the results of severe accident analysis. The chemical form of U varied depending on the local amount of Fe and O. In regions of low steel content, the U-containing metallic phase was dominated by 
-(Zr,U)(O), while regions of high steel content were dominated by Fe
(Zr,U) (Laves phase). A few percent of U was transferred to the metallic phases under reducing conditions, raising challenging issues on the chemical removal of nuclear material from fuel debris.
Brissonneau, L.*; Ikeuchi, Hirotomo; Piluso, P.*; Gousseau, J.*; David, C.*; Testud, V.*; Roger, J.*; Bouyer, V.*; Kitagaki, Toru; Nakayoshi, Akira; et al.
Journal of Nuclear Materials, 528, p.151860_1 - 151860_18, 2020/01
Times Cited Count：17 Percentile：87.70(Materials Science, Multidisciplinary)Kitagaki, Toru; Ikeuchi, Hirotomo; Yano, Kimihiko; Brissonneau, L.*; Tormos, B.*; Domenger, R.*; Roger, J.*; Washiya, Tadahiro
Journal of Nuclear Science and Technology, 56(9-10), p.902 - 914, 2019/09
Times Cited Count：8 Percentile：61.40(Nuclear Science & Technology)Nakayoshi, Akira; Ikeuchi, Hirotomo; Kitagaki, Toru; Washiya, Tadahiro; Bouyer, V.*; Journeau, C.*; Piluso, P.*; Excoffier, E.*; David, C.*; Testud, V.*
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR 2019) (Internet), 4 Pages, 2019/05
Bouyer, V.*; Journeau, C.*; Haquet, J. F.*; Piluso, P.*; Nakayoshi, Akira; Ikeuchi, Hirotomo; Washiya, Tadahiro; Kitagaki, Toru
Proceedings of 9th Conference on Severe Accident Research (ERMSAR 2019) (Internet), 13 Pages, 2019/03
Kitagaki, Toru; Ikeuchi, Hirotomo; Yano, Kimihiko; Ogino, Hideki; Haquet, J.-F.*; Brissonneau, L.*; Tormos, B.*; Piluso, P.*; Washiya, Tadahiro
Progress in Nuclear Science and Technology (Internet), 5, p.217 - 220, 2018/11
Ikeuchi, Hirotomo; Piluso, P.*; Fouquart, P.*; Excoffier, E.*; David, C.*; Brackx, E.*
Proceedings of 8th European Review Meeting on Severe Accident Research (ERMSAR 2017) (Internet), 12 Pages, 2017/05
no abstracts in English
-based simulated fuel debris in nitric acidIkeuchi, Hirotomo; Ishihara, Miho; Yano, Kimihiko; Kaji, Naoya; Nakajima, Yasuo; Washiya, Tadahiro
Journal of Nuclear Science and Technology, 51(7-8), p.996 - 1005, 2014/07
Times Cited Count：11 Percentile：62.20(Nuclear Science & Technology)Ikeuchi, Hirotomo; Kondo, Yoshikazu*; Noguchi, Yoshihiro*; Yano, Kimihiko; Kaji, Naoya; Washiya, Tadahiro
Proceedings of International Nuclear Fuel Cycle Conference; Nuclear Energy at a Crossroads (GLOBAL 2013) (CD-ROM), p.1349 - 1356, 2013/09
Yano, Kimihiko; Kitagaki, Toru; Ikeuchi, Hirotomo; Wakui, Ryohei; Higuchi, Hidetoshi; Kaji, Naoya; Koizumi, Kenji; Washiya, Tadahiro
Proceedings of International Nuclear Fuel Cycle Conference; Nuclear Energy at a Crossroads (GLOBAL 2013) (CD-ROM), p.1554 - 1559, 2013/09
Ikeuchi, Hirotomo; Sano, Yuichi; Shibata, Atsuhiro; Koizumi, Tsutomu; Washiya, Tadahiro
Journal of Nuclear Science and Technology, 50(2), p.169 - 180, 2013/02
Times Cited Count：10 Percentile：59.45(Nuclear Science & Technology)An efficient dissolution process was established for future reprocessing in which MOX fuels with high plutonium contents and dissolver solution with high heavy-metal concentrations will be treated. This dissolution process involves short stroke shearing of fuels (10 mm in length). The dissolution kinetics of irradiated mixed-oxide fuels and the effects of the Pu content, heavy-metal concentration and fuel form on the dissolution rate were investigated. Irradiated fuel was decreased with increasing Pu content. Kinetic analysis based on the fragmentation model indicated that the dissolution rate of irradiated fuel was affected not only by the volume ratio of liquid to solid (
ratio), but also by the exposed surface area (
ratio). The penetration rate of nitric acid is expected to be decreased at high heavy-metal concentrations by a reduction in the ratio, but enhanced by shearing the fuel pieces with short strokes and thus enlarging the ratio.
Inoue, Masaki; Ikeuchi, Hirotomo; Takeuchi, Masayuki; Koyama, Shinichi; Suto, Mitsuo
JAEA-Research 2011-057, 100 Pages, 2012/03
JAEA-Research-2011-057.pdf:3.23MB
Corrosion resistance of fuel pin cladding tube materials is one of the most important properties to design aqueous reprocessing process. The martensitic oxide dispersion strengthened ferritic steel, names as "9Cr-ODS" steel, is the primary candidate of high burnup fuel pin cladding tube for fast reactor cycle. Because 9Cr-ODS steel contains lower chromium than stainless steels, oxidizing species in nitric acid medium needs to reduce its corrosion rate. In spent fuel dissolvers, although both nitric acid and metallic ions concentrations change, corrosion potential of 9Cr-ODS steel tends to increase gradually and stabilize protective passive layer effectively.
Ikeuchi, Hirotomo; Shibata, Atsuhiro; Sano, Yuichi; Koizumi, Tsutomu
Procedia Chemistry, 7, p.77 - 83, 2012/00
Times Cited Count：20 Percentile：97.37(Chemistry, Analytical)The effects of Pu content were studied on the dissolution rate of irradiated mixed oxide fuel and on the mass of insoluble residue. Kinetic analysis was conducted being based on the surface-reaction model to estimate the dissolution rate of irradiated fuels with Pu contents less than 30% and with burn-up ranging from 40.1 - 63.7 GWD/t. The dissolution rate of irradiated mixed-oxide fuels was found to decrease exponentially with an increase of the Pu content, but those were estimated to be up to 1000 times larger than those of non-irradiated fuels with the same Pu content. The amount of insoluble residue was found to increase with increase of the Pu content, possibly due to the promotion of fission product formation. Up to 1.3% of initial heavy metal was remained as the residue.
