Numerical simulation of oxygen mass transfer dynamics in liquid lead-bismuth eutectic alloy in solid-phase active control system

In lead-bismuth eutectic (LBE) cooled nuclear reactors, the solid-phase oxygen control technique enables rapid adjustment of oxygen concentration in liquid LBE by controlling the dissolution of solid lead oxide, thereby significantly reducing the excessive slag formation. A numerical particle-resolved mass transfer model was developed to investigate the oxygen concentration dynamics within an LBE solid-phase oxygen control loop. The results indicate that the Sherwood number increases greatly with the Peclet number and the predictions show good agreement with the previous correlations. The turbulent diffusion of oxygen in LBE is much greater than its laminar diffusion. At varying temperature, due to the combined effect of dissolution and diffusion, the oxygen mass transfer coefficient reaches the peak at approximately 500 °C. In the mass exchanger with binary particle packing, the dissolution rate of the bed with 8 mm and 10 mm spheres, in which the pressure drop is lower, is comparable to that of 6 mm spheres and higher than other sizes. In the cases involving the prolate and oblate ellipsoids, with higher mass transfer area, dissolution rate is higher at lower aspect ratios. The turbulence contribution of the bed with oblates is greater and the performance of the solid-phase oxygen control is improved.