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
Room temperature comfortable warmth is for normal, healthy adults who are appropriately dressed. For those with respiratory problems or allergies, they recommend no less than , and for the sick, disabled, very old or very young, a minimum of . Temperature ranges are defined as "room temperature" for certain products and processes in industry, science, and consumer goods. For instance, for the shipping and storage of pharmaceuticals, the United States Pharmacopeia-National Formulary (USP-NF) defines "controlled room temperature" as between , with excursions between allowed, provided the mean kinetic temperature does not exceed . The European Pharmacopoeia defines it as being simply ,