Advanced CFD analysis of impurity formation and transport in liquid Lead-Bismuth Eutectic (LBE) loop systems

The lead-cooled fast reactor is a promising fourth-generation advanced nuclear reactor, utilizing liquid Lead-Bismuth Eutectic (LBE) coolant with stable chemical properties, high density, and a high boiling point. However, LBE faces challenges like corrosion and oxidation, leading to insoluble iron and lead oxides forming particulate impurities. These impurities nucleation, migration, and accretion, affecting fluid dynamics, composition distribution, and reactor circulation capacity with implications for reactor safety and economic viability. To address these issues, this study employs Computational Fluid Dynamics (CFD) to simulate impurity behavior in a liquid LBE loop system. Mathematical and physical models are developed to describe impurity formation, migration, nucleation and accretion. The study also explores bidirectional coupling between impurity particles and oxygen concentration in LBE, offering insights into impurity properties and distribution over time. The developed numerical model effectively captures the key characteristics of impurity behavior in non-isothermal lead–bismuth eutectic (LBE) loops. Under saturated oxygen conditions, the model predicts the onset of nucleation at 1.9 s, stabilizing at a production rate of 1.82 × 10⁻¹⁰ kg/s. It accurately reproduces the spatial variation of particulate growth and dissolution driven by temperature gradients, with the maximum growth rate reaching 1.09 × 10⁻⁹ m/s. The simulation further reveals the tendency of impurities to preferentially accumulate at flow discontinuities, where the maximum accretion thickness of impurity particles grows to a thickness of 1.70 μm after 10,000 s of operation. Critically, the results indicate that in the absence of proper control measures, impurity accumulation may cause millimeter-scale flow blockages within 1600 h, posing significant operational risks to the reactor system. These findings will inform strategies for managing impurities in LBE systems, enhancing reactor performance and reliability.