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Kato, Chiaki; Yamamoto, Masahiro; Tsukada, Takashi
Zairyo To Kankyo 2009 Koenshu, p.29 - 32, 2009/05
This research was performed through systematization of assessment techniques of SCC in austenitic stainless steel for in-vessel components and piping in BWR in order to develop a technical basis necessary to improve evaluation methods of the stress corrosion cracking (SCC). Recently, discrepancy between laboratory data and field experiences in crack initiation and crack growth rate was reported. JSME appendices for flaw evaluation can conservatively explain the crack growth rate in field experiences, while it is indicated the crack growth rate is slower in field experiences than in the crack growth rate reference curve of JSME. The crack growth rate reference curve would be more conservative in SCC assessment of field experiments. Therefore, a prediction model in crack initiation and propagation is expected in order to explain failure time reasonably and accurately in the crack propagation. On the other hand, it was reported that hydrogen peroxide under radiolysis water accelerated crack propagation. This accelerating factor has not been considered in SCC assessment techniques at present. The objective of this research is to summarize the present situation of SCC assessment techniques and to study issues of the technique from viewpoints of discrepancy between field experiences and laboratory data.
Sato, Tomonori; Miwa, Yukio; Tsukada, Takashi; Uchida, Shunsuke
Zairyo To Kankyo 2009 Koenshu, p.63 - 66, 2009/05
At the surface of a pure metal, a particular half cell reaction corresponding to an exposed water chemistry condition occurs. In principle, O
and HO concentrations in high temperature water can be determined by the comparison of the redox potential responses of some kind of pure metals corresponding to exposed condition. In order to confirm the concept of sensor, responses of the redox potentials of pure metals to the changes in O and HO concentrations were measured under non-irradiated condition and compared with the calculated potentials.
Motooka, Takafumi; Yamamoto, Masahiro; Ueno, Fumiyoshi; Kato, Chiaki
no journal, ,
The effect of chromium and vanadium ions on corrosion of stainless steels in boiling nitric acid solutions were investigated in terms of valence change with time. The corrosion behavior of type SUS304ULC stainless steel in boiling nitric acid solutions was investigated by corrosion test, measurement of corrosion potential and solution analysis. The formation rates of Cr(VI) and V(V) were also measured in boiling nitric acid solutions. Cr(VI) more severely attacked the stainless steel than V(V). The concentration of Cr(VI) reduced with progress of corrosion and the oxidation ability of test solution weakened. While the concentration of V(V) was constant with progress of corrosion and the oxidation ability of test solution was maintained constant. In boiling nitric acid solutions, the formation rate of V(V) from reducdant was faster than that of Cr(VI). In boiling nitric acid solution with V(V), the formation rate of V(V) was faster than the consumed rate of V(V) by corrosion of stainless steel. This caused the constancy of V(V) concentration and the steady corrosion of stainless steel. In boiling nitric acid solution with Cr(VI), the formation rate of Cr(VI) was slower than the consumed rate of Cr(VI) by corrosion of stainless steel. This caused the decreases of Cr(VI) concentration and corrosion rate of stainless steel.