First nuclear reaction safely initiated marks latest step prior to generation of electricity ATLANTA, Feb. 14, 2024 /PRNewswire/ -- Georgia Power announced today that Unit 4 at the Vogtle nuclear expansion project near Waynesboro, Georgia, has safely reached initial criticality. Initial criticality is a key step during the startup testing sequence and demonstrates that -- for the first time -- operators have safely started the nuclear reaction inside the second reactor. This means atoms are being split and ...