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. At the same time, we will develop a new corrosion prevention technology that has excellent basic applicability to PCVs and has
Kakiuchi, Kazuo; Amaya, Masaki; Udagawa, Yutaka
Annals of Nuclear Energy, 171, p.109004_1 - 109004_9, 2022/06
JAEA-Research 2021-019, 24 Pages, 2022/05
In order to reduce the corrosion rate of materials in molten lead bismuth eutectic (LBE), it is important to adjust the oxygen concentration, and past reports show that the oxygen concentration is often adjusted to about 10 to 10wt%. However, it is not clearly stated what concentration is optimal, and there are some reports of severe corrosion even within this concentration range. In this study, a corrosion model considering diffusion in oxide and LBE was developed for 9Cr-1Mo steel, and the corrosion control method estimated from the corrosion model were investigated. We also tried to calculate the optimum oxygen concentration to prevent the flow blockage at the low temperature of loop environment while reducing the corrosion of 9Cr-1Mo steel in molten LBE. As a result, it was expected that the corrosion mode of 9Cr-1Mo steel in LBE could be classified into three types, dense film formation, precipitation film formation, and film dissolution, depending on the ratio of oxide film thickness to diffusion layer thickness, iron concentration in LBE, and temperature. In order to inhibit corrosion, it is important to adjust the oxygen concentration so that the conditions for dense film formation can be maintained. For this purpose, it was expected that a pre-oxidized film of more than 10m should be applied before immersion in LBE. The oxygen concentration of about 10 to 10wt% is the appropriate oxygen concentration when the oxide film has grown to some extent, and a higher oxygen concentration was expected to be required when the film is thin.
Purazuma, Kaku Yugo Gakkai-Shi, 98(5), p.211 - 215, 2022/05
Lead-bismuth eutectic (LBE) alloy is promising as a spallation target for next-generation reactor coolants and accelerator drive systems (ADS) due to its nuclear and chemical properties. LBE is a heavy metal, and it has good properties both as a spallation target and as a coolant for nuclear transmutation systems of long-lived radioactive nuclei. On the other hand, to improve compatibility with structural materials is one of the major issues in its utilization. The latest research results such as high-temperature operation of LBE and oxygen concentration control to ensure corrosion resistance with the aim of early commercialization of nuclear conversion technology by ADS is introduced.
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
) 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.
Collaborative Laboratories for Advanced Decommissioning Science; National Institute for Materials Science*
JAEA-Review 2021-059, 71 Pages, 2022/02
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 (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 genetic and electrochemical diagnosis and inhibition technologies for invisible corrosion caused by microorganisms" conducted in FY2020. The present study aims to develop innovative diagnostic techniques such as accelerated test specimens and on-site genetic testing for microbially induced and accelerated corrosion of metallic materials (microbially influenced corrosion, MIC), and to identify the conditions that promote MIC at 1F for proposing methods to prevent MIC through water quality and environmental control. We also aim to develop a research base based on materials, microorganisms, and electrochemistry, to develop technologies that can be used by engineers in the field, and to cultivate leade
Kitayama, Ayami; Taniguchi, Naoki; Mitsui, Seiichiro
Materials and Corrosion, 72(1-2), p.211 - 217, 2021/01
Umeda, Ryota; Shimoyama, Kazuhito; Kurihara, Akikazu
Nihon Genshiryoku Gakkai Wabun Rombunshi, 19(4), p.234 - 244, 2020/12
Sodium-water reaction caused by failure of the steam generator tube of sodium-cooled fast reactor induce the wastage phenomenon, which has erosive and corrosive feature. In this report, the authors have performed the self-wastage experiments under high sodium temperature condition to evaluate the effect of wastage form/geometry by using two types of initial defect such as the micro fine pinhole and fatigue crack, and water leak rate on self-wastage rate. Based on the consideration of crack type influence, it was confirmed that self-wastage rate did not strongly depend on the initial defect geometry. As a mechanism of the self-plug phenomenon, it is speculated that sodium oxide intervenes and inhibits the progress of self-wastage. The dependence of initial sodium temperature on self-wastage rate was clearly observed, and new self-wastage correlation was derived considering the initial sodium temperature.
Furusawa, Akinori; Takenaka, Yusuke; Nishimura, Akihiko
Applied Sciences (Internet), 9(17), p.3544_1 - 3544_12, 2019/09
Remote-controlled, non-destructive testing is necessary to detect corrosion of the reinforced concrete structures at the Fukushima Daiichi Nuclear Power Plant (NPP) de-commissioning site. This work aims to demonstrate that laser-induced ultrasonic guided wave technology can be applied to achieve this task. Hence, accelerated electrolytic corrosion is performed on a reinforced concrete specimen fabricated by embedding a steel rod into mortar. Waveforms of the laser-induced ultrasonic guided wave on the rod are measured with a previously employed piezoelectric transducer (PZT) probe, for each fixed corrosion time. Based on the results of Fourier and wavelet transforms of the waveforms, issues concerning the detection and extent of rebar corrosion are discussed. It is exhibited that the changes in bonding strength due to corrosion are distinguishable in the frequency domain of the ultrasonic signal.
Hanawa, Satoshi; Hata, Kuniki; Chimi, Yasuhiro; Kasahara, Shigeki
Proceedings of 21st International Conference on Water Chemistry in Nuclear Reactor Systems (Internet), 12 Pages, 2019/09
Irisawa, Eriko; Yamamoto, Masahiro; Kato, Chiaki; Motooka, Takafumi; Ban, Yasutoshi
Journal of Nuclear Science and Technology, 56(4), p.337 - 344, 2019/04
Taniguchi, Naoki; Nakayama, Masashi
Zairyo To Kankyo, 67(12), p.487 - 494, 2018/12
This article describes the current status of corrosion monitoring methods and examples of the measurement under deep underground environments for carbon steel overpacks for high-level radioactive waste disposal. Based on the studies on corrosion monitoring using AC Impedance technique, some of the typical measurement systems such as the electrodes arrangement are introduced. In-situ corrosion monitoring in engineering scale test is also being attempted using a deep underground research facility, and the measurement method and results are presented in this article.
Takahatake, Yoko; Ambai, Hiromu; Sano, Yuichi; Takeuchi, Masayuki; Koizumi, Kenji; Sakamoto, Kan*; Yamashita, Shinichiro
Proceedings of Annual Topical Meeting on Reactor Fuel Performance (TopFuel 2018) (Internet), 9 Pages, 2018/10
The corrosion behaviour of FeCrAl-ODS steels for the accident tolerant fuel cladding of LWRs were investigated in nitric acid solutions for the reprocessing process of spent fuels. The corrosion tests were carried out at 60C, 80C and the boiling point of the solutions, and the specimens were then analysed by XPS. The corrosion remarkably progressed at the boiling point, and the highest corrosion rate was 0.22 mm/y. In the oxide film, the atomic concentration of Fe was lower, than that in the base material, and those of Cr and Al were higher. The results show that the corrosion of FeCrAl-ODS steels in hot nitric acid solution is not severe because of the high corrosion resistance of the oxide film formed on the material; hence, the corrosion resistance of the new cladding materials in the dissolution process of spent fuel is acceptable for reprocessing operations.
Yamamoto, Masahiro; Soma, Yasutaka; Igarashi, Takahiro; Ueno, Fumiyoshi
Proceedings of Annual Congress of the European Federation of corrosion (EUROCORR 2018) (USB Flash Drive), 7 Pages, 2018/09
In order to clarify the SCC behavior of SUS316L under BWR environment, mass transfer inside crevice of SUS316L in high temperature water using various crevice gap samples was investigated. The samples were prepared by put together two SUS316L sheets. Crevice gap differs from 0.005 mm to 0.1 mm. Corrosion tests were conducted in 8 ppm dissolved oxygen (DO) conditions. Surface oxide film was analysed by laser Raman spectroscopy (LRS) after immersion. Numerical simulations were also conducted by using COMSOL Maltiphysics. Diffusion process of DO and the other chemical species were calculated with connected to electrochemical process. Electrical conductivities inside the crevice were 100 times larger than these of outer water. The reason of high conductivity is existence of Fe ions at the DO depletion crevice.
Yamamoto, Masahiro; Sato, Tomonori; Igarashi, Takahiro; Ueno, Fumiyoshi; Soma, Yasutaka
Proceedings of European Corrosion Congress 2017 (EUROCORR 2017) and 20th ICC & Process Safety Congress 2017 (USB Flash Drive), 6 Pages, 2018/09
The authors have studied the differences between outer surface and the crevice-like portion of SUS316L in high pressurized and high temperature water containing dissolved oxygen. We have already introduced that changes in the characteristics of corrosion products along the crevice directions and gap width. It is suggested that the environmental conditions are different with the features of crevice from these results. In this report, we introduce the changes in oxide films with crevice gaps and comparison with the numerical simulation data utilizing of FEM calculation.
JAEA-Technology 2018-006, 43 Pages, 2018/08
The Horonobe URL Project has being pursued by JAEA to enhance the reliability of relevant disposal technologies through investigations of the deep geological environment within the host sedimentary formation at Horonobe, Hokkaido. The URL Project proceeds in 3 overlapping phases, "Phase I: Surface-based investigations", "Phase II: Investigations during tunnel excavation" and "Phase III: Investigations in the underground facilities", over a period of around 20 years. The OP corrosion test was prepared from 2013 FY at Niche No.3, and heating by electric heater in simulated overpack started in November, 2014. The objective of the test is acquiring data concerned with corrosion of carbon steel OP. These data will be used in order to confirm the performance of engineered barrier system. In the OP corrosion test, the diameter of simulated OP and buffer material are 100 mm and 300 mm, respectively. Concrete support using low alkaline cement was used in order to investigate the effect of cementitious materials to OP corrosion behavior. We will measure corrosion potential of carbon steel, natural potential, pH in buffer material for several years. In this report, we describe how to make simulated OP and buffer material blocks, and set sensors, and so on.
Wan, T.; Saito, Shigeru
Metals, 8(8), p.627_1 - 627_22, 2018/08
Uchida, Shunsuke*; Hanawa, Satoshi; Naito, Masanori*; Okada, Hidetoshi*; Lister, D. H.*
Corrosion Engineering, Science and Technology, 52(8), p.587 - 595, 2017/10
Based on the relationship among ECP, metal surface conditions, exposure time and other environmental conditions, a model to evaluate the ECP and corrosion rate of steel was developed by coupling a static electrochemical analysis and a dynamic oxide layer growth analysis. Major conclusion obtained on the model are as follows. The effect of HO and O concentrations on ECP were successfully explained as the effects of oxide layer growth. Hysteresis of ECP under changes in water chemistry conditions were successfully explained with the model. Decreases in ECP due to neutron exposure were explained well by radiation-induced diffusion in the oxide layers.