Nuclear Power

07 Mar 2023

Vogtle 3 reaches initial criticality, marking pivotal nuclear startup milestone

07 Mar 2023  by powermag   

Plant Vogtle Units 3 and 4 are the first nuclear plants to be built in the United States in 30 years. This photo shows Vogtle 3 under construction in January 2023. Georgia Power has curated a photographic history of the project here. Courtesy: Georgia Power

Vogtle 3, one of two 1,117-MW Westinghouse AP1000 reactors Southern Nuclear Operating Co. is building in Georgia, has reached initial criticality. The event marks a pivotal milestone for the Generation III+ pressurized water reactor (PWR) American advanced nuclear reactor—the first of its kind built in the U.S.

“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 reactor,” Georgia Power, a Southern Co. subsidiary, on March 6. Georgia Power co-owns the Vogtle expansion, comprising Vogte 3 and 4 with Oglethorpe Power, MEAG Power, and Dalton Utilities. “This means atoms are being split and nuclear heat is being made, which will be used to produce steam.”

The reactor now continues startup 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 synchronizing the generator to the electric grid and begin producing electricity,” Georgia Power said. “Then, operators will continue increasing power through multiple steps, ultimately raising power to 100%.”

The tests will ensure all systems operate successfully together. They will also validate operating procedures. The unit will be declared commercially operational if the tests are successfully completed. According to Georgia Power, the in-service date for Unit 3 is projected “during May or June 2023.”

As POWER recently reported, Southern Co. anticipates the projected schedule for Unit 3 primarily depends on the progression of final component and pre-operational testing and startup, “which may be impacted by further equipment, component, and/or other operational challenges.” The delays could also affect the in-service date for Unit 4. According to Southern Co.’s Feb. 16–issued annual report, Unit 4 is slated to be placed in service during the late fourth quarter of 2023 or in the first quarter of 2024.

“We remain focused on safely bringing this unit online, fully addressing any issues and getting it right at every level,” said Chris Womack, chairman, president, and CEO of Georgia Power, on Monday. “Reaching initial criticality is one of the final steps in the startup process and has required tremendous diligence and attention to detail from our teams,” he added.

“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 U.S. This is a truly exciting time as we prepare to bring online a new nuclear unit that will serve our state with clean and emission-free energy for the next 60 to 80 years,” Womack said.

The Long Journey to the Major Milestone

The milestone is the latest of several achievements Southern Nuclear has accomplished over the massive project’s timeframe to develop and build Vogtle 3 and 4. Construction of the two reactors (Vogtle 3 and 4)— the first new nuclear units built in the U.S. in the last three decades—kicked off in 2009, with plans to put the reactors online by 2016 and 2017. Four utilities share the project’s ownership interests: Southern Co.’s Georgia Power subsidiary (45.7%); Oglethorpe Power Corp. (OPC, 30%), Municipal Electric Authority of Georgia (MEAG, 22.7%), and Dalton Utilities (1.6%).

Delays, however, have reportedly pushed project costs up to at least $30.3 billion. Costs reported by MEAG in May 2022 suggested total spending for the expansion was close to $34 billion. Southern Co., in its latest annual report, projected Georgia Power’s share of the full capital cost forecast to complete Plant Vogtle Units 3 and 4, including contingency, through the end of the second quarter of 2023 and the first quarter of 2024, respectively, will be $10.6 billion.


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