Georgia Power, a subsidiary of Atlanta-based Southern Co, announced unit 4 at the Vogtle NPP has reached initial criticality, with the unit's in-service date now projected to be during the second quarter of 2024. Earlier in February, Georgia Power said vibrations found in a cooling system of Vogtle 4 meant further delays. Previously operation was set for 30 March.

Vogtle 3&4 are both 1,117 MWe Westinghouse AP1000 pressurised water reactors (PWRs). The two units were originally expected to cost about $14bn and to enter service in 2016 and 2017 but suffered a series of delays, including Westinghouse’s bankruptcy in 2017. The total cost of the project to build Vogtle 3&4 is now put at more than $30bn. Georgia Power owns 45.7% of the project; Oglethorpe Power Corp owns 30%; the Municipal Electric Authority of Georgia (MEAG) owns 22.7%; and the city of Dalton owns 1.6%. The units will be operated by Southern Nuclear.

The reactor's power output will now be raised to prepare it for synchronisation to the electric grid, and the start of electricity generation. Operators will take the unit through a gradual power increase until it reaches its full power output. Tests to ensure all systems are operating together and to validate operating procedures will be carried out throughout the start-up process before the unit is declared to be in commercial operation.

The Vogtle site already hosts to two operating pressurised water reactors. Unit 3 – the first new nuclear unit to be built in the USA for more than three decades – reached initial criticality in March 2023, and began commercial operation in July. Fuel loading at Vogtle 4 began in August 2023.

Image: Vogtle unit 4 (courtesy of Georgia Power)