Nuclear

Vogtle Unit 3 reaches first criticality

Operators will continue to raise power to support synchronizing the generator to the electric grid, ultimately raising power to 100%. 
Vogtle Unit 3 reaches first criticality
Vogtle Unit 4 (left) and Unit 3 (right). Credit: Georgia Power

Operators have safely started the nuclear reaction at Vogtle Unit 3, 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.

Startup testing will continue at the 1,100 MW Vogtle Unit 3. 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. 

Operators will continue to raise power to support synchronizing the generator to the electric grid, ultimately raising power to 100%. 

Vogtle Units 3 and 4 are the first nuclear units to be built in the U.S. in more than three decades. However, cost overruns and construction problems have delayed the project. Additionally, project partners have disputed over rising construction costs and their stake in the venture.

The in-service date for Unit 3 is now projected to be May or June. Southern Nuclear will operate the new units on behalf of the co-owners, Georgia Power, Oglethorpe Power, MEAG Power and Dalton Utilities.

In February, Georgia Power once again pushed back the in-service date. This came after Southern Nuclear identified and began working to repair equipment and component issues that led to vibrations in cooling system piping.

The utility said in a mid-February filing with U.S. securities regulators that the unit’s schedule primarily depended on the “progression of final component and pre-operational testing” and start-up. It warned that the in-service date could be delayed by further equipment, component, and other operational challenges. 

In January, the utility said that extending the in-service date beyond the first quarter could result in additional base capital costs of up to $15 million pre-tax per month, as well as related allowance for funds used during construction and any additional related construction, support resources, or testing costs.

In its filing with regulators, the utility said that after considering the timeframe and duration of hot functional and other testing and recent experience with Unit 3, the 1,100 MW Unit 4 facility is now projected to enter service during the late fourth quarter of 2023 or the first quarter of 2024. 

That unit’s schedule depends on potential impacts arising from Unit 4 testing activities that overlap with Unit 3 start-up and commissioning, the utility said. The schedule also hinges on maintaining overall construction productivity and production levels, particularly in subcontractor scopes of work, and maintaining appropriate levels of craft laborers. 

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