Corrosion kinetics of T91 steel under low oxygen conditions (10−7 wt% O) in lead-bismuth eutectic at 500 °C

Abstract

Among the advanced reactor designs of the fourth generation, the Lead-cooled Fast Reactor (LFR) stands out as one of six distinct types. The corrosion caused by the liquid Lead-Bismuth Eutectic (LBE) on structural materials is recognized as a significant obstacle hindering the development of LFR. The corrosion kinetics of T91 steel in static LBE with 10−7 wt% oxygen at 500 ºC is analyzed in this study. The formed oxide scale consists of an outer (Fe, Cr)3O4 layer with a Fe-Cr spinel structure and an inner internal oxidation zone (IOZ). The thickness evolution of the oxide layers follows a parabolic rule, with rate constants determined for different layers. The dissolution rate of metals into the LBE decreases over time, indicating diminishing the concentration gradient of Fe across the oxide layer-LBE interface. The observed deviations from expected norms may be attributed to dynamic flow conditions and non-isothermal loop experiments, which accelerate Fe diffusion into LBE.