Improved cellular automata modeling of corrosion/oxidation mechanism of stainless steel in LBE

Abstract

In recent years, small modular reactors (SMRs) have garnered significant attention, and small modular natural circulation lead or lead-alloy-cooled fast reactors (LFRs) are among the potential choices for SMR development. However, the issue of metal corrosion in a high-temperature environment by liquid lead–bismuth eutectic (LBE) persists in small modular natural circulation LFRs. The primary current method for addressing this problem involves dissolving a certain amount of oxygen in LBE to form an oxide layer on the inner surface of the piping as a corrosion inhibitor. The structural evolution of the oxide layer on stainless steel surfaces under the influence of LBE is a complex nonlinear process. Existing experiments and research have indicated that the oxide layer is a biphasic oxide layer. However, due to the limited and scattered results from current experimental studies, predicting the long-term corrosion of steel in liquid lead–bismuth alloys remains a challenge. To further understand the formation principles of the biphasic oxide layer and the factors influencing its formation process, this study established a cellular automata model that combines surface growth and internal corrosion oxidation to simulate the corrosion of stainless steel, the diffusion of iron/oxygen elements on the oxide layer, and the precipitation of iron on the oxide layer using the cellular automata method. The diffusion process was simulated using a random walk model. The approximate characteristics of the evolution of the involved processes were explored based on the simulation results. The simulation results showed that the cellular automata method can accurately simulate the formation of the biphase oxide film in this complex process from a mesoscopic scale.