Vogtle Unit 4 reaches first criticality
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Vogtle Unit 4 reaches first criticality

Operators have safely started the nuclear reaction at Vogtle Unit 4, according to an announcement from Georgia Power.

This step, known as initial criticality, happens when the nuclear fission reaction becomes self-sustaining and is necessary to generate enough heat to produce electricity. Operators will now continue increasing power through multiple steps, ultimately raising power to 100 percent.

Startup testing will continue at Unit 4. This includes demonstrating the integrated operation of the primary coolant system and steam supply system at design temperature and pressure with fuel inside the reactor. 

Georgia Power recently said because of vibrations in the reactor’s cooling system, Unit 4 would not start commercial operation until sometime in the second quarter of 2024, or between April 1 and June 30.

The company said its construction budget won’t be affected if Unit 4 starts by June 30 but it would have to pay $15 million a month in extra construction costs if the project extends into July.

The utility said in a filing to investors that the vibrations “were similar in nature” to those experienced during startup testing for Unit 3, which began commercial operations last summer.

Vogtle Units 3 and 4, two AP-1000 reactors each with a capacity of approximately 1,100 MW, are the first new units to be built in the U.S. in more than 30 years. Cost overruns and construction problems have long delayed the project.

The new Vogtle reactors are currently projected to cost Georgia Power and three other owners $31 billion, according to calculations by The Associated Press. Add in $3.7 billion that original contractor Westinghouse paid Vogtle owners to walk away from construction, and the total nears $35 billion.

The reactors were originally projected to cost $14 billion and be completed by 2017.

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