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Irisawa, Eriko; Kato, Chiaki
Journal of Nuclear Materials, 591, p.154914_1 - 154914_10, 2024/04
Times Cited Count:0 Percentile:0.08(Materials Science, Multidisciplinary)The amount of corrosion of austenitic stainless-steel R-SUS304ULC was evaluated considering the changes in solution composition and boiling during actual concentration operations. Austenitic stainless-steel R-SUS304ULC is the structural material of the highly radioactive liquid waste concentrator in Japanese spent fuel reprocessing plant, which treats highly corrosive nitric acid solutions during enrichment operations. The study results show that it is necessary to focus on nitric acid concentrations, oxidizing metal ion concentrations, and decompression boiling as factors that accelerate the corrosion rate of stainless steel because of cathodic reaction activation.
Koyama, Motomichi*; Yamashita, Takayuki*; Morooka, Satoshi; Sawaguchi, Takahiro*; Yang, Z.*; Hojo, Tomohiko*; Kawasaki, Takuro; Harjo, S.
Tetsu To Hagane, 110(3), p.197 - 204, 2024/02
Times Cited Count:0Koyama, Motomichi*; Yamashita, Takayuki*; Morooka, Satoshi; Yang, Z.*; Varanasi, R. S.*; Hojo, Tomohiko*; Kawasaki, Takuro; Harjo, S.
Tetsu To Hagane, 110(3), p.205 - 216, 2024/02
Times Cited Count:0Okitsu, Takayuki*; Hojo, Tomohiko*; Morooka, Satoshi; Miyamoto, Goro*
Tetsu To Hagane, 110(3), p.260 - 267, 2024/02
Times Cited Count:0Otani, Kyohei; Kato, Chiaki; Igarashi, Takahiro
Corrosion, 79(11), p.1277 - 1286, 2023/11
Suzuki, Seiya; Arai, Yoichi; Okamura, Nobuo; Watanabe, Masayuki
Journal of Nuclear Science and Technology, 60(7), p.839 - 848, 2023/07
Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)The fuel debris, consisting of nuclear fuel materials and reactor structural materials, generated in the accident of Fukushima Daiichi Nuclear Power Plant can become deteriorated like rocks under the changes of environmental temperature. Although the fuel debris have been cooled by water for 10 years, they are affected by seasonal and/or day-and-night temperature changes. Therefore, in evaluating the aging behavior of the fuel debris, it is essential to consider the changes in environmental temperature. Assuming that the fuel debris are deteriorated, radioactive substances that have recently undergone micronization could be eluted into the cooling water, and such condition may affect defueling methods. We focused on the effect of repeated changes in environmental temperature on the occurrence of cracks, and an accelerated test using simulated fuel debris was carried out. The length of the crack increases with increasing number of heat cycle; therefore, the fuel debris become brittle by stress caused by thermal expansion and contraction. In conclusion, it was confirmed that the mechanical deterioration of the fuel debris is similar to that of rocks or minerals, and it became possible to predict changes in the length of the crack in the simulated fuel debris and environmental model.
Li, S.; Yamaguchi, Yoshihito; Katsuyama, Jinya; Li, Y.; Deng, D.*
Proceedings of ASME 2023 Pressure Vessels and Piping Conference (PVP 2023) (Internet), 7 Pages, 2023/07
Suzuki, Kenji*; Miura, Yasufumi*; Shiro, Ayumi*; Toyokawa, Hidenori*; Saji, Choji*; Shobu, Takahisa; Morooka, Satoshi
Zairyo, 72(4), p.316 - 323, 2023/04
Collaborative Laboratories for Advanced Decommissioning Science; Tohoku University*
JAEA-Review 2022-069, 114 Pages, 2023/03
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 FY2020, this report summarizes the research results of the "Development of a new corrosion mitigation technology using nanobubbles toward corrosion mitigation in PCV system under the influence of //-rays radiolysis" conducted in FY2021. In this work, in order to ensure the long-term reliability of steel structures that ensure important confinement functions in the debris removal process, such as existing PCVs and newly constructed negative pressure maintenance systems and piping, corrosion phenomena in wet environments where - and -ray emitting nuclides come into contact with steel are clarified for the first time.
Mohamad, A. B.; Nakajima, Kunihisa; Miwa, Shuhei; Osaka, Masahiko
Journal of Nuclear Science and Technology, 60(3), p.215 - 222, 2023/03
Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)Wang, Y.*; Tomota, Yo*; Omura, Takahito*; Gong, W.; Harjo, S.
Materialia, 27, p.101685_1 - 101685_9, 2023/03
Aoyama, Takahito; Kato, Chiaki
Corrosion Science, 210(2), p.110850_1 - 110850_10, 2023/01
Times Cited Count:2 Percentile:15.81(Materials Science, Multidisciplinary)The chelated complex of Cu: [Cu(EDTA)] was used to introduce Cu from outside to the inside of crevice. The introduced Cu was expected to act as an inhibitor for the crevice corrosion on stainless steels. Crevice corrosion tests, confirmed the introduction of Cu to the inside of the crevice via electromigration of [Cu(EDTA)] was confirmed. Migrated [Cu(EDTA)] reacted with H and inhibited decrease in pH inside the crevice, where Cu was separated from [Cu(EDTA)] and suppressed active dissolution of the stainless steel.
Emura, Yuki; Takai, Toshihide; Kikuchi, Shin; Kamiyama, Kenji; Yamano, Hidemasa; Yokoyama, Hiroki*; Sakamoto, Kan*
Journal of Nuclear Science and Technology, 10 Pages, 2023/00
Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)Koyama, Motomichi*; Yamashita, Takayuki*; Morooka, Satoshi; Sawaguchi, Takahiro*; Yang, Z.*; Hojo, Tomohiko*; Kawasaki, Takuro; Harjo, S.
ISIJ International, 62(10), p.2036 - 2042, 2022/10
Times Cited Count:11 Percentile:61.61(Metallurgy & Metallurgical Engineering)Koyama, Motomichi*; Yamashita, Takayuki*; Morooka, Satoshi; Yang, Z.*; Varanasi, R. S.*; Hojo, Tomohiko*; Kawasaki, Takuro; Harjo, S.
ISIJ International, 62(10), p.2043 - 2053, 2022/10
Times Cited Count:7 Percentile:30.25(Metallurgy & Metallurgical Engineering)Collaborative Laboratories for Advanced Decommissioning Science; Tohoku University*
JAEA-Review 2022-002, 85 Pages, 2022/06
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 "Development of a new corrosion mitigation technology using nanobubbles toward corrosion mitigation in PCV system under the influence of //-rays radiolysis" conducted in FY2020. In this work, in order to ensure the long-term reliability of steel structures that ensure important confinement functions in the debris removal process, such as existing PCVs and newly constructed negative pressure maintenance systems and piping, corrosion phenomena in wet environments where - and -ray emitting nuclides come into contact with steel are clarified for the first time.
Ogawa, Fumio*; Nakayama, Yuta*; Hiyoshi, Noritake*; Hashidate, Ryuta; Wakai, Takashi; Ito, Takamoto*
Transactions of the Indian National Academy of Engineering (Internet), 7(2), p.549 - 564, 2022/06
The strain energy-based life evaluation method of Mod. 9Cr-1Mo steel under non-proportional multiaxial creep-fatigue loading is proposed. Inelastic strain energy densities were calculated as the areas inside the hysteresis loops. The effect of mean-stress has been experimentally considered and the relationship between inelastic strain energy densities and creep-fatigue lives was investigated. It was found from the investigation of hysteresis loops, the decrease in maximum stress leads to prolonged failure life, while stress relaxation during strain holding causes strength reduction. The correction method of inelastic strain energy density was proposed considering the effect of maximum stress in hysteresis loop and minimum stress during strain holding, and strain energy densities for uniaxial and non-proportional multiaxial loading were obtained. Based on these results, the mechanisms governing creep-fatigue lives under non-proportional multiaxial loading have been discussed.
Momma, Yuichiro*; Sakairi, Masatoshi*; Ueno, Fumiyoshi; Otani, Kyohei
Zairyo To Kankyo, 71(5), p.133 - 137, 2022/05
The effect of the corrosion inhibitor on the corrosion of steel under a thin solution layer was investigated. As a result of forming a thin solution layer with a thickness of 1.0-0.2 mm on the specimen, adding a mixed solution of sodium molybdate and aluminum lactate as a corrosion inhibitor, and performing electrochemical measurement, the corrosion inhibitor suppresses the anodic reaction. And in the thin solution layer, it was suggested that the morphology of the protective layer structure by the corrosion inhibitor changed according to the amount of liquid as compared with the bulk immersion.
Momma, Yuichiro*; Sakairi, Masatoshi*; Ueno, Fumiyoshi; Otani, Kyohei
Zairyo To Kankyo, 71(4), p.121 - 125, 2022/04
The effect of solution layer thickness on the atmospheric corrosion of carbon steel was investigated using novel devices fabricated by a 3D printer. These novel devices allowed us to control the solution layer thickness precisely. Potentiodynamic polarization measurements were performed under thickness-controlled solution layer, and oxygen diffusion limiting current density () and anodic current density () were measured. As the solution layer become thinner, increased and decreased. This result indicates that corrosion accelerates when the solution layer becomes thinner. The diffusion coefficient of oxygen was calculated as 3.2010 cm s from the relationship between and solution layer thickness, and the critical diffusion thickness was estimated to be 0.87 mm.
Irisawa, Eriko; Kato, Chiaki; Yamashita, Naoki; Sano, Naruto
Zairyo To Kankyo, 71(3), p.70 - 74, 2022/03
In order to evaluate the corrosion of stainless steels used in spent nuclear fuel reprocessing facilities, the immersion corrosion tests and polarization measurements were performed using R-SUS304ULC stainless steel in nitric acid solution containing a kind of radionuclides, Np. At temperatures above 328 K, the corrosion potential was higher than that in nitric acid solution and was near the transpassive region. From the comparison between the corrosion amount calculated by the immersion corrosion tests and the polarization resistance, the values of =0.018-0.025 V were obtained as a conversion factor, and the possibility of calculating the corrosion amount from the electrochemical measurement was examined.