TVA pulls Sequoyah nuclear reactors offline
Hours before the Tennessee Valley Authority asked customers of its local utilities to use less electricity, operators took the Sequoyah Nuclear Plant completely offline to address malfunctions, according to reports from the U.S. Nuclear Regulatory Commission.
Two nuclear reactors at the plant in Soddy-Daisy can generate enough electricity for up to 1.3 million homes at peak performance.
TVA needs that power as temperatures soar into the mid- to upper-90s across its seven-state service region, driving up demand for electricity and putting strain on its grid. The federal agency asked its local utilities to conserve energy Tuesday morning.
Neither reactor experienced an emergency, and the non-nuclear malfunctions had no impact on health or safety to plant personnel or the public, TVA reported to the regulatory agency.
But the manual trips extended a series of chronic nuclear outages plaguing the nation’s largest public power provider since last year.
(UPDATE: TVA gets Sequoyah nuclear reactor back online after outage)
Operators manually tripped Sequoyah’s Unit 1 reactor early Tuesday to address low water levels in a steam generator caused by a malfunction in a control system, the reports show.
They manually tripped the Unit 2 reactor around 4 a.m. to address a similar problem caused by a valve malfunction.
EPB, Chattanooga’s local utility that buys power wholesale from TVA, sent out a power advisory six hours later asking customers to reduce their power use at TVA’s request.
“I wouldn’t try to tie the two events together, because we have a diverse fleet,” TVA spokesperson Scott Fiedler said in a phone interview. “Those are things that we do take into account.”
As the utility’s nuclear output plunged overnight Tuesday from 8,213 megawatts to 5,910 megawatts by 5 a.m., TVA turned to natural gas and its pumped storage facility, according to data from the U.S. Energy Information Administration.
From 5 a.m. to noon, TVA ramped up generation at its natural gas plants from 6,418 megawatts to 10,401 megawatts, according to the administration’s data. That’s an increase in output enough to power more than 2 million homes, according to calculations used by TVA.
(READ MORE: TVA nuclear outages continue into summer, undoing plans)
The federal agency turned to the Raccoon Mountain Pumped Station Reservoir overlooking Chattanooga. That facility operates like a giant battery, storing water on a mountain and releasing it through turbines when it’s needed most.
TVA’s early data showed the highest demand on Tuesday was 30,813 megawatts, Fiedler said. The utility projected a peak demand of around 31,800 megawatts Wednesday as the average temperature across its region reached 95 degrees.
GAS FILLS IN
For a brief moment Monday, all seven nuclear reactors were generating electricity at or near full capacity, fulfilling on overdue projection from TVA that its fleet would be running like normal through the summer.
TVA has experienced a series of nuclear outages affecting all three of its nuclear plants since last summer. The electrical generator at Sequoyah Unit 2 tripped in July, prompting an expensive replacement.
TVA generated more electricity from its natural gas plants than from its nuclear plants between Jan. 1 and March 31, according to a quarterly financial report, an anomaly for a utility that prides itself on strong nuclear performance.
Under normal operations, TVA would get around 40% of its power from its three nuclear plants and 23% from its 17 natural gas plants. During the second quarter of its fiscal year, it sourced 28% of its power from natural gas plants and 27% from nuclear plants.
“This once again calls into question what resources we consider reliable and what have been dubbed unreliable,” Maggie Shober, research director at the Knoxville-based Southern Alliance for Clean Energy, said in a phone interview.
“If you have an 80-megawatt solar plant go down, that’s fairly replaceable,” Shober said. “If you have over 2 gigawatts go down in the course of a couple hours, that’s difficult to replace on a regular day, and this week, we are not seeing regular days.”
If TVA had more solar farms and battery storage, the nuclear outages could be more easily addressed, Shober said. The Southern Alliance for Clean Energy is one of many environmental groups in the region pushing TVA to expand its solar generation faster and slow its expansion of fossil fuel plants.
Solar and wind energy, mostly purchased from other utilities, make up around 4% of TVA’s grid. The utility says it plans to have 10,000 megawatts of solar power by 2035.
When TVA turns to natural gas, it passes the cost of the fuel to customers through local power companies. But that’s not the only cost that can rise during nuclear outages.
”TVA is purchasing power on the market,” Shober said. “This heat wave is not exclusive to TVA, so prices are pretty high, and those costs actually get passed on directly to customers.”
AGING PLANTS
The federal utility, based in Knoxville with an operations base in Chattanooga, had three of its seven nuclear reactors down during a TVA board of directors meeting in May.
The utility’s chief nuclear officer told the board the problem would be addressed quickly.
(READ MORE: Lost tax credits may mean canceled Tennessee energy projects)
“We expect all seven to be delivering safe and reliable power this month,” Tim Rausch said at the May 8 meeting. “We expect those within the next week, actually, to return those three units to service.”
Some of the outages were routine scheduled maintenance and refueling outages, but the plants are expected to run continuously for around 18 months between refuelings.
TVA managers have pointed to the age of the utility’s nuclear plants and the expiration of electrical equipment. Browns Ferry, the oldest nuclear plant and the highest output plant in TVA’s system, celebrated 50 years in 2024. The Sequoyah reactors came online in 1981 and 1982.
Two units at the Watts Bar Nuclear Plant in Rhea County came online in 1996 and 2016, the latter of which became the first new U.S. nuclear reactor to come online in the 21st century.
TVA plans to invest around $6 billion over the next decade to extend the life of its nuclear plants to 80 years or longer, a process that requires license extensions from the Nuclear Regulatory Commission.
Contact Daniel Dassow at ddassow@timesfreepress.com or 423-757-6318.