NaK Liquid Metal Used for Reactor Coolant
When the EBR-I team first proposed the Uranium 235 pile, they had very specific requirements for the liquid to be used for cooling the reactor. They knew the device would be subject to high temperatures due to the heat released by the fission reaction. Owing to excellent heat transfer properties as well as its extremely low melting point which made it a liquid metal at room temperature, a sodium potassium alloy known as NaK was chosen. Used as a reactor coolant, the NaK then transferred the heat to water that then turned to steam. This steam powered a turbine that created electricity by turning a generator. Of course, NaK burns when exposed to air, and can explode when exposed to water. These volatile characteristics of the material required special pumps to circulate the hot NaK. Also, a unique NaK piping containment with an Argon-gas system was created so that if there was a leak the coolant would not come into contact with air.