ATLANTA – The nuclear expansion at Georgia Power’s Plant Vogtle has reached another milestone as it nears completion after years of cost overruns and scheduling delays.

Unit 4, the second of two new reactors being built at the plant south of Augusta, achieved 100% power on Monday night, the Atlanta-based utility announced.

“Achieving 100% power is the latest milestone as we work to complete Unit 4 as a reliable, emission-free new energy source for Georgia,” according to a statement released by Georgia Power.

“Our teams continue testing for the unit, including safely running at various power levels and operating through real-life conditions, just as it will over the next 60 to 80 years after the unit enters commercial operation.”

Unit 3 at Vogtle went into full commercial operation last summer. Unit 4 is expected to begin operations between this month and June.

The Georgia Public Service Commission (PSC) voted in December to let Georgia Power pass on to customers almost $7.6 billion of its costs in building the two additional nuclear reactors at Plant Vogtle, the first in the United States since the 1980s.

The project was originally expected to cost $14 billion when the PSC approved it in 2009 but has more than doubled due to a series of cost overruns and delays in the construction schedule. The project will increase the average monthly residential customer’s bill by $8.95.