On 6 March Georgia Power announced that the 1117 MW Unit 3 of its Vogtle nuclear power plant has safely reached initial criticality during the start-up testing sequence, demonstrating that for the first time operators have safely started the nuclear reaction inside the reactor.

A reactor achieves criticality when the nuclear fission reaction becomes self-sustaining. Achieving initial criticality is necessary to continue the start-up of the Unit in order to generate sufficient heat for the production of electricity.

Chris Womack, chairman, president and CEO of Georgia Power commented: “When you consider the history of safe and reliable operations at Vogtle Units 1 and 2 for decades now, it puts today’s milestone in perspective that Plant Vogtle will be a four-unit site making it the largest of its kind in the US. This is a truly exciting time as we prepare to bring online a new nuclear unit that will serve our state … for the next 60 to 80 years.” 

Vogtle Unit 3 continues with start-up testing to demonstrate the integrated operation of the primary coolant system and steam supply system at design temperature and pressure with fuel inside the reactor. Now that the Unit 3 reactor has reached criticality, operators will continue to raise power to support synchronising the generator to the electric grid. Then operators will continue increasing power through multiple steps, ultimately raising power to 100 %. These tests are designed to ensure all systems are operating together and to validate operating procedures prior to declaration of Commercial Operation. The in-service date for Unit 3 is projected during May or June 2023. Southern Nuclear will operate the new units on behalf of the co-owners Georgia Power, Oglethorpe Power, MEAG Power and Dalton Utilities.

Vogtle units 3 and 4 will be the first new nuclear units built in the United States in more than three decades. They employ the Westinghouse AP1000 pressurised water reactor technology. Unit 4 is projected to be complete in either late Q4 2023 or Q1 2024.

Image: Vogtle Unit 3 (courtesy of Georgia Power)