Up to now, molten salts are often used for heat transport and heat storage at higher temperatures. As a drawback, they are limited to maximal operating temperature of ~600°C, are very aggressive at temperatures above about 550 °C and lead to heavy corrosion. However, higher temperatures are necessary to improve the efficiency of solar-thermal devices. In contrast, sodium is a good candidate for high temperature applications. Its physical material properties are well suited; among others, its melting point is at about 100 °C and its boiling point at nearly 900 °C at atmospheric pressure, giving a wide temperature range for single-phase applications without the need to design high-pressure systems. In addition, it is more appropriate for applications with cyclic transients. It is a proven coolant technology on industrial scale, and our institute worked to this aspect for many years. As a disadvantage of sodium, the interactions with water and with air in case of leakages have to be considered. However, several safety measures, passive and active components can be considered to ensure the safe operation of sodium facilities.