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Vogtle Unit 4 reaches initial criticality

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 nuclear heat is being made, which will be used to produce steam. 

A reactor achieves criticality when the nuclear fission reaction becomes self-sustaining. Achieving initial criticality is necessary to continue the startup of the unit in order to generate sufficient heat for the production of electricity. Vogtle Unit 4 continues with startup testing, which demonstrates the integrated operation of the primary coolant system and steam supply system at design temperature and pressure with fuel inside the reactor. These tests are designed to ensure all systems are operating together and to validate operating procedures prior to declaration of commercial operation.

Now that the Unit 4 reactor has reached criticality, operators will continue to raise power to support synchronizing the generator to the electric grid and begin producing electricity. Then, operators will continue increasing power through multiple steps, ultimately raising power to 100 percent.

Vogtle Unit 3 entered commercial operation on July 31, 2023, and is providing safe, reliable, emission-free energy to Georgia today. The in-service date for Unit 4 is projected during the second quarter of 2024.

The new Vogtle units are an essential part of Georgia Power's commitment to delivering clean, safe, reliable and affordable energy to its 2.7 million customers. When operating, each of the new units can produce enough electricity to power an estimated 500,000 homes and businesses. Southern Nuclear will operate the new units on behalf of the co-owners: Georgia Power, Oglethorpe Power, MEAG Power and Dalton Utilities.

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