Georgia's Vogtle nuclear plant expansion is already years behind schedule and billions of dollars over budget, and it may get delayed once again.

The Georgia Public Service Commission Public Interest Advocacy staff this week published an evaluation of the most recent reassessment of project timeline and cost for Vogtle Units 3 and 4. The good news: the staff concluded that the latest analysis by Southern Nuclear Company, the Southern Company subsidiary overseeing plant construction, was "generally sound."

That's notable, seeing as the staff recommended canceling Vogtle when the commission voted on a revised budget and schedule in December 2017.

The bad news: The staff doesn't believe the baseline timeline to begin operations is "achievable." That target was May 2021 and 2022 for the two reactors. Even commercial operation by November 2021 and 2022 would be "a challenge to achieve," according to the staff.

As for the price tag, the staff believes "there is a chance" of hitting $17.1 billion in capital costs, not including financing costs. Further delays would increase the project cost, however.

Delay and cost overruns have dogged Vogtle, which started the permitting process in 2005. Utility Georgia Power, the major owner and offtaker for the plant, originally filed to use the new plant for capacity in the 2016 to 2017 timeframe.

Since then, the Vogtle 3 and 4 units have earned the dubious distinction of being the last-surviving nuclear power plant under construction in the U.S. They are also the first to use the new AP1000 reactor from Westinghouse, a company whose 2017 bankruptcy threw an additional delay into the mix. Until then, Westinghouse had also served as primary contractor for the project.

The ongoing struggle prompted Department of Energy Secretary Rick Perry to dedicate another $3.7 billion in loan support in March. The DOE had already committed $5 billion in loan guarantees as of 2017.

The perils of speed

The new report indicates that Southern Company has prioritized speed of execution to avoid paying for more delays.

That decision could cause unintended consequences of its own, the authors note. To accelerate the project, the company is beginning system completion and testing before finishing up the bulk of electrical, mechanical and civil engineering work. The strategy risks "stacking of craft," a term for the physical congestion that ensues as crews performing different types of work navigate the same space in the power block.

"Staff’s concern is that the approach of achieving a minimal schedule at all costs could result in additional costs to the project without achieving the commensurate reduction in schedule needed to offset these additional costs," the report observes.

Productivity in recent months has not met "achievable" expectations, the report notes, raising concerns about lower productivity and absenteeism getting in the way of meeting those goals in future months.

Already, the remaining work is expected to be 2.5 times more dollar-intensive than the construction finished thus far. Workers have completed 77 percent of the project at a cost of $9.86 billion. The remaining 23 percent is budgeted to cost $7.243 billion, assuming it does not run over.

The potential causes of delay at this point have less to do with nuclear technology itself than with the nuts and bolts of completing massive construction projects. It doesn't help that the U.S. workforce has exceedingly little experience with massive nuclear construction, as the most recent completion, Tennessee Valley Authority's Watts Bar Unit 2, began construction in the 1970s.

"Ultimately, we need to move away from nuclear power plants as these big infrastructure projects with lots of people doing artisanal craftsmanship and move toward factory fabrication," said Jessica Lovering, director of energy at The Breakthrough Institute and a researcher studying how innovation could make nuclear power cheaper.

Despite the bloated price tag, round-the-clock production over decades of project lifetime could yield a favorable levelized cost of energy, Lovering added. If completed, these units will also be the first to benefit from a federal Production Tax Credit for new nuclear generation.

Even if Vogtle does meet the challenging timelines, it is unlikely that similarly large plants will be built in the U.S. going forward, especially after South Carolina's V.C. Summer plant fell through and left ratepayers with billions of dollars of charges for a project that never generated a single kilowatt-hour.

Going forward, small modular reactors offer a lower-cost route for nuclear plant development, but they have not yet cleared the regulatory process.