Historical Perspective on Reactor Coolants

* In the 1950s and 1960s, scientists and engineers considered (and in many cases built) nearly everything imaginable at the time:
– Water (light, heavy)
– Liquid-metal (NaK, sodium, lithium, mercury, rubidium, lead, bismuth, lead-bismuth, gallium, tin, etc. and numerous other alloys)
– Gas (air, argon, carbon dioxide, helium, hydrogen, nitrogen)
– Fluid Fuel (aqueous: UO2/phosphoric acid, U(SO4)2, UO2SO4/ThO2; molten salt: NaF-BeF2-UF4, LiF-BeF2-ZrF4-UF4/FLiBe; liquid metal: U-Bi)
– Organic (polyphenyls/terphenyls, kerosene, Santowax)

* Combinations of coolant and moderator were also studied:
– Sodium-cooled, graphite moderated (SRE, Hallam)
– Organic-cooled, heavy water moderated (Whiteshell 1, ESSOR)