Staff Photo / Both cooling towers are in operation at the Watts Bar Nuclear Plant in 2016.

The cost of replacing the steam generators at America's newest nuclear reactor swelled to nearly $600 million and took weeks longer than originally expected to install this spring when windy weather prolonged the outage at the Watts Bar Unit 2 reactor.

Despite the cost and delays, TVA officials said this week the new equipment should help ensure the long-term viability of TVA's newest nuclear unit as a source of carbon-free, reliable power for decades ahead. With the completion of the equipment repairs at Watts Bar on July 1, TVA has now replaced and upgraded all of the steam generators in its four pressurized water reactors and expects to save time and money during refueling outages in the future while getting extra power from the new generators.

TVA's analysis of the new generators indicates the utility will save an estimated $14 million per refueling outage compared to the old steam generators, TVA spokesman Jim Hopson said in a phone interview. In recognition of TVA's analysis of the steam generators and the performance of the new GE version of the generators, the Nuclear Energy Institute recently presented TVA its top industry award for innovation.

"A team of our engineers discovered that replacement steam generators made with improved material would have a much slower rate of wear than the original equipment, allowing less frequency of inspections, improving safety and reducing costs," TVA President Jeff Lyash said during a conference call with analysts this week. "Our employees have built a culture of continuous improvement, and this award shines a light on the powerful results that can be implemented across the nuclear industry."


Despite the industry praise, critics of nuclear power said the need to replace the steam generators at Watts Bar Unit 2 less than six years after its startup is another example of how the capital costs of nuclear power plants continue to be more than originally forecast.

In 2007, when TVA decided to resurrect work on finishing a second unit at Watts Bar that the utility had been building off and on since 1973, the cost of completing the reactor was projected to be $2.5 billion. But ultimately, the unit cost $4.7 billion to complete and start by 2016.

According to a financial report this week, TVA invested another $590 million to buy and install the four steam generators within the unit 2 reactor, bringing the plant's total capital cost to more than twice what TVA estimated it would cost a decade and a half ago.

Sandy Kurtz, a Chattanooga environmental leader active in the Sierra Club and the Blue Ridge Environmental Defense League, said in a phone interview Friday that nuclear plants continue to be more costly than projected and are not worth the risks and the long-term radioactive wastes they generate.

"Watts Bar and all the other nuclear plants are way too costly for what they deliver in way of the radiation and radioactive wastes," she said.

But even with the doubling in costs, Hopson said Watts Bar Unit 2 "is still a bargain" with a price tag of only about a third of the cost of the new reactors being built at Plant Vogtle in Georgia.

"When you think about the volume of carbon-free energy that Watts Bar is able to produce 24 hours a day, seven days a week with the highest rate of reliability in the industry with the highest capacity factor, we know that these investments are absolutely in the best interests of our consumers," Hopson said.


The nuclear units can operate continuously for 18 months, delivering electricity that is not dependent upon whether the sun shines, the wind blows or the rain falls to fill hydro storage reservoirs, Hopson said.

But Watts Bar Unit 2 operated only at about 90% of its capacity in 2021 because of the problems identified with the original steam generators for the plant, which were built decades ago when construction began on the twin-reactor facility. With the new units in place, both of the 1,150-megawatt reactors at Watts Bar are operating at 100% of capacity this summer.

Installing the new generators required TVA to cut a hole in the containment building at Watts Bar to remove the old steam generators and lift the new 425-ton generators into place using one of the world's biggest cranes. When there was too much wind like there was on several days in May, TVA had to delay the use of the crane, however, Hopson said.

According to the Nuclear Regulatory Commission, the outage that started in March was originally planned to be completed in mid-May but was delayed by windy weather and other storms.

"Removing the original steam generators and installing the upgraded models, which weigh more than 800,000 pounds each, was a significant engineering and operational feat," Lyash said. "The steam generator replacement project involved more than 4,000 welds and poured more than 850,000 pounds of concrete while performing more than 26,000 work activities, including replacing 88 of the unit 2's 193 fuel assemblies."

In addition to its power generation, TVA helps the U.S. military irradiate tritium-producing burnable absorber rods at Watts Bar. The National Nuclear Security Administration is scaling up tritium output at Watts Bar and other civilian nuclear plants, but such production was delayed this year by the steam generator replacement project at Watts Bar.

Tritium boosts the power of modern thermonuclear weapons but decays often enough that the National Nuclear Security Administration must regularly replace the tritium reservoirs of each active weapon in the U.S. arsenal. Tritium from the TVA reactors is harvested at the Savannah River Site in Aiken, South Carolina.

Contact Dave Flessner at or 423-757-6340. Follow on Twitter at @Dflessner1