Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
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.
Nemoto, Yoshiyuki; Kaji, Yoshiyuki; Onizawa, Takashi*; Kanazawa, Toru*; Nakashima, Kazuo*; Tojo, Masayuki*
Proceedings of Annual Congress of the European Federation of Corrosion (EUROCORR 2018) (USB Flash Drive), 8 Pages, 2018/09
The authors proposed oxidation models based on oxidation data which previously obtained in high temperature oxidation tests on small sample of Zircalloy-2 (Zry2) cladding in dry air and in air/steam mixture environment. The oxidation models were implemented in computational fluid dynamics (CFD) code to analyse oxidation behavior of long cladding sample in hypothetical spent fuel pool (SFP) accident conditions. The oxidation tests were conducted using Zry2 cladding sample 500 mm in length. The oxide layer growth in dry air was well reproduced in the calculation using the oxidation model, meanwhile which in air/steam mixture was overestimated atmosphere composition change anticipated in the spent fuel rack during the accident, and its influence on the oxidation behaviour of the cladding were discussed in consideration of the oxidation model improvement.
Aoki, So; Kondo, Keietsu; Kaji, Yoshiyuki; Yamamoto, Masahiro
no journal, ,
The objective of this study was to clarify stress corrosion cracking (SCC) initiation susceptibility and corrosion behavior of grain boundaries of long-term thermal aged low carbon austenitic stainless steels in simulated BWR condition. Crevice Bent Beam (CBB) test was carried out to estimate the SCC initiation susceptibility under BWR simulated water condition. Surface and grain boundaries analysis of specimens was also carried out after the CBB test. The present results of the CBB tests showed that the SCC initiation susceptibility of Type 316L increased clearly by the combination of the cold work and the long-term thermal aging. Grain boundaries of Type 316L specimen which exhibited the SCC initiation susceptibility corroded with formation of Cr oxide, and the oxide formed along depth direction of grain boundaries. Based on these results, the correlation among SCC initiation susceptibility, SCC crack initiation and corroded grain boundaries will be discussed.
-ray irradiationSato, Tomonori; Ueno, Fumiyoshi
no journal, ,
The structural materials used in Fukushima-Daiichi Nuclear Power Plant are exposed to the water containing some impurities, e.g., seawater components, under irradiation. The hydrogen peroxide and hydrogen generated by water radiolysis under irradiation condition. It was reported that -ray irradiation enhanced the corrosion of carbon steel by the weight loss measurements in the immersion test of carbon steel under irradiation. The in-situ measurement of the electrochemical parameter during irradiation is one of the most effective approaches to investigate the effects of irradiation on the corrosion. In this study, to investigate the effects of -ray irradiation on the corrosive condition and corrosion phenomena, the in-situ electrochemical measurement method during irradiation was constructed, and the cyclic voltammetry (CV) was performed in the diluted artificial seawater under -ray irradiation conditions. The dose rate of -ray was 3.3 kGy/h, and the temperature was fixed at 50 degrees centigrade. Obtained major results are in follows;(1) The in-situ electrochemical measurements were successfully performed in this study. (2) The diffusion limiting current in the cathodic region decreased just after the start of irradiation. And then the cathodic current increased. This tendency indicated that the dissolved oxygen was consumed rapidly by the irradiation. The consumed dissolved oxygen contributed to the generation of hydrogen peroxide. (3) The cathodic current under irradiation was 20 percents larger than that before irradiation. (4) The anodic current increased just after the start of irradiation by the generation of hydrogen and hydrogen peroxide.
Sakairi, Masatoshi*; Otani, Kyohei; Islam, M. S.*
no journal, ,
Previous studies showed that zinc ion shows higher corrosion resistant property on corrosion of metals in aqueous environment. It is, however, not fully elucidate role of zinc ions on corrosion inhibition of metals in aqueous environments. In this study, the effects of zinc ion on corrosion behavior of aluminum alloy and steels in aqueous environments. From electrochemical and surface analysis results, zinc ion may forms a very effective shielding film which can block the electrochemical reactions, consequently lowers the corrosion rate.