A study of the effects of minor additives to Pb-Bi eutectic: Designing novel Pb-Bi-X liquid alloys for heat transfer applications

Abstract

Lead-bismuth eutectic (LBE) is a promising heat transfer fluid candidate for fast-neutron nuclear reactors and for concentrating solar power systems, due to its low melting point and advantageous thermophysical properties, but suffers from causing liquid-metal corrosion in many solids used as structural materials. Adding a suitable element to LBE to form a ternary alloy, along with proper oxygen concentration in LBE at desired temperature, might provide a formation of the protective intermetallic layers besides the formation of protective oxides on the solid surface. In this study, novel Pb-Bi-X alloys, as improvement LBE, have been designed for a broad temperature range, with X additions selected based on thermodynamic considerations and modeling, and experimentally evaluated at 700 °C. Thermodynamic calculations indicated Pb-Bi-Sb and Pb-Bi-Ge as the best candidates, and experiments provided some evidence of possible intermetallic formation of Sb with Fe-Cr-Al alloy constituents. The work pointed to the need for further research into the compatibility with structural materials at high temperatures. Keywords: Solar energy, Heat transfer, Liquid metal, Oxygen control, Fe-Cr-Al alloy