Oxygen control technique in molten lead and lead-bismuth eutectic systems

The key aspects of oxygen control technique used for steel corrosion mitigation in lead-alloy systems include the thermodynamic stability of protective oxides, oxygen concentration range, measurement and control methods, and oxide layer structures and transport properties. Practical conditions for oxygen control and the proper oxygen concentration ranges for typical nonisothermal liquid lead and lead-bismuth eutectic (LBE) systems are presented based on the available thermodynamic and solubility data. Theoretical expressions for the widely used oxygen sensor signals are obtained. The sensors are calibrated by comparing the experimental results from a nonisothermal LBE loop and the theoretical calculations. Analyses show that the fully turbulent flow leads to a nearly uniform oxygen concentration over the entire loop, and there is no significant delay of sensor response to a change of the operating condition. Under conditions of actively controlled oxygen in lead and LBE, the possible behaviors for oxidation, corrosion, and corrosion product precipitation are analyzed, providing the means to optimize corrosion control through oxide protection.