Liquid metal cooled reactor Clementine was the first liquid metal cooled nuclear reactor and used mercury coolant, thought to be the obvious choice since it is liquid at room temperature. However, because of disadvantages including high toxicity, high vapor pressure even at room temperature, low boiling point, producing noxious fumes when heated, relatively low thermal conductivity, and a high neutron cross-section, it has fallen out of favor. Sodium and NaK (a eutectic sodium-potassium alloy) do not corrode steel to any significant degree and are compatible with many nuclear fuels, allowing for a wide choice of structural materials. They do, however, ignite spontaneously on contact
Ionic liquid as formate, alkylsulfate, alkylphosphate or glycolate. The melting point of 1-butyl-3-methylimidazolium tetrafluoroborate is about and it is a colorless liquid with high viscosity at room temperature. If a highly asymmetric cation is combined with a highly asymmetric anion, formed ionic liquid may not freeze down to very low temperatures (down to −150 °C) and the glass transition temperature was detected below −100 °C in the case of ionic liquids with N-methyl-N-alkylpyrrolidinium cations and fluorosulfonyl-trifluoromethanesulfonylimide (FTFSI). Water is a common impurity in ionic liquids as it can be absorbed from the atmosphere and influences the transport properties of RTILs, even at