Southern Company and the Department of Energy have announced an agreement to demonstrate the world’s first fast-spectrum salt reactor in collaboration with TerraPower and a host of other participants at Idaho National Laboratory. With this announcement, at least four of the DOE’s Advanced Reactor Demonstration Project awardees featuring four different coolants—helium (X-energy), sodium (TerraPower), fluoride salt (Kairos Power), and chloride salt (Southern, with TerraPower)—have announced a site and a commitment to build either a full-size demo reactor or a scaled-down experimental reactor.