Magnetohydrodynamic Analyses of a Miniature, Dual-Stage Electromagnetic Pump for Lead and Sodium In-Pile Test Loops

To support the development of Generation IV nuclear reactors, in-pile and out-of-pile test loops with miniature, submersible direct-current electromagnetic pumps (DC-EMPs) are used to investigate compatibility and corrosion issues of nuclear fuel and structure materials with flowing molten lead and alkali liquid metals. Owing to the absence of detailed experimental measurements and because of its simplicity and low computational cost, the equivalent circuit model (ECM) is widely used to predict the pump characteristics. The simplifying assumptions in the ECM contribute to overpredicting the pump characteristics by >10%. To gain insight into the pump operation and assess the effect of various assumptions in ECM, not possible even experimentally, this work performed three-dimensional (3-D), magnetohydrodynamic (MHD) analyses of a 66.8-mm-diameter, submersible, dual-stage DC-EMP, recently developed by the authors, for circulating molten Pb and liquid Na at up to 500°C. The solution of the coupled electromagnetism equations and the momentum and energy balance equations calculates the pump characteristics and provides 3-D images of the flow, electric current, and magnetic field strength distributions in the flow duct. The grid convergence index (GCI) criterion confirmed the adequacy of the employed numerical mesh refinement and the results conversion. Results demonstrate strong dependence of the magnetic field strength distribution in the flow duct on the value and the distribution of the electric current but negligible effects of the fluid temperature on joule heating and pump characteristics. The Lorentz force highest densities occur at the entrance of the two pumping stages, and approximately 10.0% of the total force occurs in the fringe regions upstream and downstream of pumping stages. The MHD pump characteristics are in general agreement with, but consistently lower than, the ECM predictions. For molten lead and liquid sodium, the difference between the calculated characteristics increases with increased flow rate and input current, up to 12% and 14%, respectively.