Steam rises from the cooling tower of the single operating reactor at the Watts Bar Nuclear Plant in Spring City, Tenn. in this 2007 photo. Photo by TVA

ATHENS, Tenn. - The leader of an environmental group Tuesday asked nuclear regulators how they could ensure that the Watts Bar Unit 2 reactor's concrete foundation - poured 40 years ago - is still sufficient to support the nation's newest reactor expected to go online in 2015.

"Roads and bridges don't last 40 years, and you're about to license this [to operate] for another 40 years. And if you give it another 20 after that, like you usually do, by the time the plant is retired that concrete will be 100 years old," said Don Safer, board chairman of the Tennessee Environmental Council.

Robert Haag, a U.S. Nuclear Regulatory Commission construction projects chief, told Safer and about a dozen others at a hearing in Athens near the Spring City plant on Tuesday that the plant has been completely inspected.

"Is it going to be brand new? No. But ... inspections show it is capable of performing its function," Haag said.

The Watts Bar nuclear plant, with two reactors, was started first in 1973, but construction on Unit 2 was suspended in 1985. Unit 1 eventually was completed and started in 1996. Work on Unit 2 resumed in 2008. Originally expected to be completed in 2012 at a cost of $2.5 billion, the work now has dragged out to an anticipated start-up date of December 2015 and the cost has escalated to $4 billion or $4.5 billion.

NRC officials said regulatory inspectors conducted 12,488 hours of inspections on Unit 2 and another 5,186 hours of inspection on Unit 1 - the operating reactor - during 2012 alone.

The regulators held two meetings in Athens Tuesday to tell residents living around Watts Bar Nuclear Plant near Spring City, Tenn., about the proposed licensing of the still-under-construction Unit 2 reactor and to review the safety and performance of the Unit 1 reactor.

They said Unit 1 was operating in the "green," a color-coded measure of safety that NRC defines as safe and normal.

TVA officials made no address during the meeting. But after it was over, Watts Bar site vice president Tim Cleary said the utility is happy that the finding for the plant's performance and construction is green.

"They have a very rigorous process for licensing plants and they'll ensure it's safe. And we'll ensure it's safe," Cleary said.

Jim Hopson, a Watts Bar spokesman said there are no exceptions or allowances for the new reactor construction "just because it was started back in the '70s. It's got to meet today's standards - whatever those standards are."