Why is molten sodium useful as a heat-transfer fluid?

Molten sodium is considered an excellent heat-transfer fluid primarily due to its physical properties, which allow it to efficiently extract and transport thermal energy in demanding environments such as liquid-metal fast breeder reactors.12

Its utility as a coolant stems from its ability to remain in a liquid state over a wide temperature range, combined with high thermal conductivity, which facilitates the rapid transfer of heat away from a reactor core. In these systems, primary sodium circulates through the core to extract heat, which is then transferred to a secondary, nonradioactive sodium loop that powers a steam generator.32

Additionally, because the solubility of certain impurities like oxides is low in molten sodium, the fluid can be effectively purified through continuous processes such as filtration or cold trapping, ensuring the system remains operational and stable. While sodium is highly reactive, its effectiveness as a heat-transfer medium has led to its extensive use in specialized industrial and nuclear applications.41