Comparative Assessment of Liquid Sodium and Gallium as Emergency Coolants in Nuclear Energy Applications

Abstract

The influence of the thermophysical variable properties on the buoyancy-driven flows of liquid sodium and gallium established in a cylindrical cavity is numerically investigated, for the entire range of Rayleigh number corresponding to practical applications. Axisymmetric turbulent simulations (initially steady) are obtained, considering appropriate boundary and reference conditions for simulating the emergency cooling of a nuclear reactor. The results obtained for different heating intensities are analyzed and compared. In the case of sodium, the expected decay in the heat transfer coefficients is less relevant than that previously obtained for airflows. In turn, strong differences in the gallium thermal behavior are encountered. In fact, a trend opposite to that of sodium is detected for wide ranges of Rayleigh number and heating parameter. Additional transient simulations are carried out to complete a comparative assessment of the performance of both liquid sodium and gallium as cooling agents.