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
Liquid metal embrittlement rate sensitive. Temperature also affects the kinetics of LME. An increase in strain rate increases the upper limit temperature as well as the crack propagation rate. In most metal couples LME does not occur below a threshold stress level. Testing typically involves tensile specimens but more sophisticated testing using fracture mechanics specimens is also performed. Many theories have been proposed for LME. The major ones are listed below; All of these models, with the exception of Robertson, utilize the concept of an adsorption-induced surface energy lowering of the solid metal as the central cause of LME. They have succeeded in