NASHVILLE (AP) - A nuclear plant first begun in 1973, then mothballed, is on schedule to open in December 2015.

During a conference call Thursday, Tennessee Valley Authority Senior Vice President of Nuclear Construction Mike Skaggs said the Watts Bar 2 plant is on schedule and on budget at a projected cost of between $4 billion and $4.5 billion.

When complete, the plant is expected to generate about 1,100 megawatts, enough electricity to supply about 650,000 homes in the seven-state TVA region.

"Nuclear plants make a lot of energy," Skaggs said. "They're very safe and reliable."

The challenge, he said, is the time it takes to build them and the cost.

The project in Spring City, 48 miles northeast of Chattanooga, was shut down in 1985 when it was about half finished at a cost of about $1.7 billion.

As TVA began looking at meeting its customers' increasing energy needs, the board decided that completing the long-idled reactor was a good option.

Work resumed in 2008 and was scheduled to be completed in late 2012. In April 2012, TVA announced the work would not be complete until 2015 and would take about $2 billion more than the $2.5 billion originally budgeted.

The utility said at the time that its initial budget underestimated how much work was needed to finish the plant and that it wasted money by not completing more design work before starting construction.

On Thursday, Skaggs said the revised estimates remain good.

"We're meeting the targets and milestones for safety, quality and schedule," Skaggs said.

Earlier this year, the Nuclear Regulatory Commission cited TVA for purchasing parts not documented as nuclear-grade quality for Watts Bar. On Thursday, Skaggs said about 70 percent of those parts have been tested and found to be satisfactory. He expects the remaining 30 percent to be satisfactory as well.

Skaggs said the safety performance at the plant is strong, with nearly 18 million hours worked without a lost-time incident. He also said the quality of the work continues to be good, with quality control inspectors approving 96 percent or more of the work.

Skaggs said one of the challenges is meeting new safety requirements implemented after the Fukushima, Japan, nuclear meltdowns in 2011. That includes reassessing the plant's ability to withstand earthquakes and flooding.

While all nuclear plants have to meet the new requirements, Watts Bar 2 has to do so before it can get a license to operate. Other plants have more time.

Skaggs said others in the industry are watching Watts Bar 2 with interest as they evaluate whether building more nuclear plants is a good option. It is one of three nuclear plants currently under construction.

"I think they're watching our progress and the lessons we're learning," he said.

TVA is the nation's largest public utility. It provides power to about 9 million pe ople in Alabama, Georgia, Kentucky, Mississippi, North Carolina, Tennessee and Virginia.