Georgia Power said commercial operation of the new Unit 3 at Plant Vogtle has been delayed for at least another month. The utility on June 16 said there’s a problem in the hydrogen system used to cool the main electrical generator.

Unit 3, part of a two-reactor expansion at the plant near Waynesboro, Georgia, had been expected to start sending electricity to the power grid this month, but the start date has now been pushed back to July at the earliest.

The generator at issue is not part of the reactor, but is located in another building at the site. That building is where steam from the heat created by fission in the nuclear reactor is sent to spin the turbine that generates electricity. Officials said the problem was caused by a degraded hydrogen seal in the main generator, which was discovered during the start-up and pre-operational testing of the unit. Georgia Power reported the situation in a regulatory filing Friday and said repairs are ongoing.

Multiple Delays and Cost Overruns

The Vogtle expansion, which was originally expected to come online seven years ago, has endured multiple delays and significant cost overruns, pushing its total cost to about $35 billion. The expansion is adding two 1,117-MW Westinghouse AP1000 pressurized water reactors to two existing reactors at Plant Vogtle that have operated since 1987 and 1989, respectively.

Georgia Power on Friday said testing of Unit 3 is about 95% complete, and the unit already has operated at full power as part of the testing process prior to entering commercial operation.

“Once all startup testing is successfully completed and the unit is available for safe, reliable dispatch, Vogtle Unit 3 will enter commercial operation,” Georgia Power spokesperson Jacob Hawkins said in a statement.

Further delays would add to the expansion’s price tag. Southern Co., parent of Georgia Power, in April told its shareholders that a three-month delay for Unit 3 would add $45 million to construction costs for the utility, which owns 45.7% of the expansion project. Other owners include Oglethorpe Power, the Municipal Electric Authority of Georgia, and the city of Dalton in Georgia, which provide power for electric cooperatives and municipal utilities. Those groups also have contracts to sell electricity produced at Vogtle to off takers in Alabama and Florida.

Unit 4 at Vogtle also has been moving through the testing process, with fuel loading expected this summer. That reactor is expected to enter commercial operation between December 2023 and March 2024.

Units 3 and 4 at Plant Vogtle are the first new commercial nuclear reactors to be built in the U.S. in more than 30 years.

Darrell Proctor is a senior associate editor for POWER (@POWERmagazine).