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How is the sodium-potassium alloy used in nuclear reactors?

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A periodic table element box for potassium shows atomic number 19, symbol K, atomic weight 39.0983, electron configuration [Ar]4s1, and name potassium. Icons indicate it is an alkali metal, solid at room temperature, body-centered cubic crystal structure, and has strongly basic higher-valence oxides. A key explains the symbols for alkali metals, solid state, body-centered cubic structure, and strong basicity. — potassium Properties of potassium.

Sodium-potassium alloy (NaK) is used to a limited extent as a heat-transfer coolant in certain fast-breeder nuclear reactors.1

As a coolant, the alloy serves to carry the thermal energy produced by fission away from the reactor fuel. It transports this heat through the system, ultimately moving it to the steam-generating equipment of the nuclear power plant. Because the alloy is a good conductor of heat, it is effective at managing the high temperatures generated during the fission process.21