Sodium is used as a coolant in nuclear power reactors because it (1) is inexpensive and readily available since large quantities are produced for industrial use; (2) has good heat transfer properties at low pressure, permitting design of high-temperature, low pressure primary heat transfer systems; and (3) does not have a high neutron capture cross section for fast neutrons, facilitating the design of a breeder reactor core. Since 1957, approximately 15 sodium-cooled reactors have operated, for the most part successfully. The United States, Soviet Union, Britain, France, Germany, and Japan all have large test and/or demonstration facilities operating or scheduled for startup. A schematic of a sodium-cooled power reactor is shown in Figure 1.
