ATLANTA — A new inspection of the nuclear expansion at Plant Vogtle the Nuclear Regulatory Commission (the NRC) announced this week could further postpone completion of the long-delayed project.

Donald Grace of Critical Technologies Construction, who serves as an independent monitor of the project, testified Thursday the NRC probe marks “an increased level of oversight” of the addition of two nuclear reactors at the plant south of Augusta.

“The fact the NRC is now getting involved … adds an additional degree of uncertainty over how long it’s going to take to get to the fuel load,” Grace told members of the Georgia Public Service Commission (PSC) during a hearing.

Prime contractor Southern Nuclear Operating Co. began hot functional testing of Unit 3, the first of two new reactors being built at Plant Vogtle, in April. The testing is conducted to make sure the reactor is ready for fuel loading, one of the final steps before the unit can go into commercial operation.

But fuel loading has been put on hold pending the outcome of the NRC inspection, which will focus on electrical cable systems needed to make sure safety-related equipment is powered to function properly.

William Jacobs of GDS Associates, another independent monitor, said the contractor found more than 600 cases of cable separation throughout the plant that need to be corrected.

“This is a big deal,” he said. “It reflects on … quality assurance, the quality control processes that were in place.”

Jacobs said hot functional testing of Unit 3 was delayed by a 60% failure rate of components needed to conduct the test.

The NRC inspection is just the latest of a series of delays that have plagued the nuclear expansion since the PSC approved the project 12 years ago. A major factor holding up the work was the bankruptcy of Westinghouse Electric, the project’s original prime contractor.

Georgia Power Co. and three utility partners underwriting the project originally expected the Unit 3 reactor to be completed in 2016, followed a year later by the second reactor, Unit 4.

The latest estimate is that Unit 3 won’t go into commercial operation until at least the first quarter of next year, followed by Unit 4 by the end of 2022.

The delays have run up the project’s price tag to nearly double the original $14 billion estimate.

On Thursday, Jacobs attributed much of the construction shortcomings the project has experienced to a rushed schedule. For example, the contractor committed to completing hot functional testing, a process that normally takes six months, in fewer than four.

“They have put production as a priority over quality,” Jacobs said. “They’ve got their production goals, and they’re intent on meeting them.”

Thursday’s hearing was part of a review of the project’s status the PSC undertakes every six months. As part of that, Georgia Power is requesting the commission to verify and approve $670 million in spending the project incurred during the last half of last year.

Despite their criticisms of the project, the independent monitors recommended that the PSC approve the spending.

Steven Hewitson, a lawyer representing Georgia Power, noted that recommendation in his cross-examination of the monitors.

Hewitson conceded the cable separation issue was a construction mistake, but he said errors are bound to occur in such a complex project.

“No one would expect on a project of this magnitude there would be 100% construction completion without some mistakes,” he said.

The NRC inspection is scheduled to take just two weeks.

But Steven Roetger, a member of the PSC’s Advocacy staff, said the probe could expand, depending on what the inspectors find.

The inspection team will release its findings and conclusions in a report to be issued within 45 days of completing its review.