Natural circulation transient thermal-hydraulic analysis and corrosion precipitation study in a LBE flow loop

The natural circulation of the lead-bismuth loop is crucial for the heat removal in both normal and accident conditions of reactor operation. Corrosion precipitation within the non-isothermal loop significantly impact the structural materials inside the reactor, making it essential to conduct an in-depth study of the transient thermal-hydraulic behavior and corrosion precipitation in the lead-bismuth loop. Mathematical modeling of our UPBEAT loop was performed, and thermal-hydraulic procedures and corrosion precipitation programs applicable to transient natural circulation were developed. Detailed investigations were carried out on the transient thermal-hydraulic behavior under typical conditions such as startup and power transients. Additionally, the distribution of corrosion precipitation in the loop under anaerobic and solid-phase oxygen control was explored. The research results indicate that during startup, there is significant temperature fluctuation in the lead-bismuth loop, and both power transients and an increase in inlet temperature lead to an enhancement in natural circulation flow. Severe corrosion was observed in the lead-bismuth loop during natural circulation operation under anaerobic control. By using a modified loop oxygen consumption predictive model to calculate the maximum corrosion rate under solid-phase oxygen control, it was found to be significantly lower than the corrosion rate under anaerobic conditions. Furthermore, an increase in heating power results in an elevated corrosion precipitation rate in the natural circulation loop. The distribution of loop corrosion precipitation is consistent under both anaerobic and solid-phase oxygen control conditions.