One of the major challenges for the Canadian Gen IV Super-Critical Water-cooled Reactor (SCWR) concept is the selection of fuel cladding materials. The Canadian SCWR concept will operate at a core outlet temperature of 625 °C and 25 MPa of pressure with peak cladding temperature reaching as high as 800 °C. Corrosion resistance is an important factor for material selection. Austenitic stainless steels that contain Cr contents greater than 18 wt.% are generally considered to provide adequate corrosion resistance. In this work, the pressure dependence of the corrosion of austenitic stainless steel 310 containing 24 wt% Cr is assessed at 625 °C for exposures of 1000 hours to evaluate the suitability of superheated steam as a surrogate for supercritical water at 25 MPa. Transmission Electron Microscopy (TEM) revealed that 310 exposed to different pressure conditions at 625 °C. (i.e., 0.1, 8 and 29 MPa) had generally the same type of the oxide structure, i.e., a Cr-rich oxide with the spinel structure on outer surface adjacent to the water phase. The material exposed at 8 and 29 MPa had a double layer oxide structure, with the outer oxide layer having a much larger grain size, while the samples exposed at 0.1 MPa showed only a single spinel-phase oxide layer. Cr-depleted recrystallized austenite grains were found underneath the spinel phase oxide. The adjacent large-grained austenite substrate had M23C6 carbides in the grain interior. The implications of these results are discussed.

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Keywords Austenitic stainless steel 310, Corrosion mechanism, Super-Critical Water-cooled Reactor
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Li, W. (W.), Woo, O.T. (O. T.), Guzonas, D. (D.), Li, J. (J.), Huang, X, Sanchez, R. (R.), & Bibby, C.D. (C. D.). (2016). Effect of pressure on the corrosion of materials in high temperature water. In Characterization of Minerals, Metals, and Materials 2015 (pp. 99–106). doi:10.1007/978-3-319-48191-3_12