Nuclear energy is usually the Tennessee Valley Authority’s largest source of electricity, but use plummeted this past year as outages plagued all seven reactors owned by the utility.
TVA reported 14 unplanned or maintenance outages over a 13-month period, according to a WPLN News review of data from the U.S. Nuclear Regulatory Commission. TVA did not respond to multiple requests for comment to verify the number of outages.
At least 12 of the outages were “forced,” meaning they were unplanned, while two were likely planned for maintenance purposes.
The longest outage happened at TVA’s Sequoyah Nuclear Plant in Soddy-Daisy, Tenn., which has two reactors. The main generator at the second reactor failed in July 2024. TVA undertook additional nuclear life extension projects during the extended, 11-month outage, and the new generator should last another 40 years, according to TVA spokesperson Scott Fiedler. On June 24, 2025, just one day after TVA brought this unit back online, the entire nuclear plant failed due to a water shortage during a heatwave.
Two weeks later — and on the same day as a forced outage at the Watts Bar Nuclear Plant — TVA’s top nuclear official Tim Rausch resigned. Rausch joined TVA in 2018 and managed the entire nuclear fleet, making $14 million between fall 2018 and fall 2024, according to the utility’s financial filings to the U.S. Securities and Exchange Commission. He plans to step down by March 2026, halfway into the next fiscal year.
Occasional nuclear outages are not inherently unsafe. None of the outages were directly related to the nuclear reactors.
“The fact that it’s a forced outage doesn’t mean danger,” Todd Allen, a professor of nuclear engineering at the University of Michigan, told WPLN News earlier this year. “Sometimes it can be as simple as a piece of critical equipment stops working as it normally would.”
But outages are a risk to reliability and costs.
Nuclear drops to lowest share of nuclear mix since 2007
TVA owns seven reactors across the Sequoyah, Watts Bar and Browns Ferry plants.
The plants collectively account for about a fifth of TVA’s total energy capacity. TVA generally keeps its nuclear plants running at all times, except when refueling uranium, so nuclear is usually about 40% of the utility’s total energy use in a normal year.
But nuclear use dropped by about 30 percent between Sept. 1, 2024 and June 30, 2025 compared to the same period the year before, according to TVA.
The utility replaced more than 90% of that lost power with fossil fuels.
“That generation was offset with natural gas, purchased power, which is primarily natural gas, and very strong performance by the coal fleet this year,” Tom Rice, TVA’s chief financial officer, said during a board meeting in August.
Nuclear power represented just 31% of TVA’s power mix in the first nine months of the fiscal year. TVA had not reported a share of nuclear power that low since 2007, when the utility was 64% coal, 30% nuclear, 6% hydroelectric and less than 1% gas or renewable during that fiscal year.
TVA’s power mix caused more air pollution and planet-warming emissions this past year due to increased fossil fuel burning. Mining or drilling for methane and coal releases methane into the atmosphere, pipelines transporting methane can leak, and burning coal and methane at power plants releases carbon dioxide, along with other toxic air pollutants. TVA’s fossil fuel plants are among the biggest single-source climate polluters in Tennessee, with the Cumberland and Gallatin plants consistently ranking as the top two, according to the U.S. Environmental Protection Agency.
The outages also likely increased monthly bills for residents across the valley.
‘Forced outages caused TVA to use more expensive sources’
TVA bought more fuel in the form of methane and coal, instead of uranium, and more gas-fired power from other companies this past year. This means that TVA was forced to buy more expensive power than it would have if the nuclear reactors were operational.
TVA initially denied that the outages impacted bills. Upon further questioning from WPLN News, the utility said that fuel costs went up because of the outages — and fuel costs affect how local power companies like the Nashville Electric Service charge monthly bills to customers. Unplanned outages can be particularly costly during extreme heat or cold events, such as when the entire Sequoyah plant failed during a heatwave in July.
“The forced outages caused TVA to use more expensive sources including natural gas and purchased power to maintain our industry-leading reliability. Fuel expenses are higher than projected for FY25 so far,” TVA spokesperson Scott Brooks said in an email.
While TVA was able to fill in the lost power, a high number of outages is a reliability concern, according to Allen, the professor.
During the Sequoyah outage in July, for example, TVA activated its “emergency load curtailment program” and asked residents to voluntarily lower their energy usage hours after the reactors failed — without disclosing the outages.
“If you take a reactor down, that’s a lot of capacity that you take down,” Allen said.
Over this past year, state officials and folks in the power industry have been watching the utility’s other nuclear developments, as TVA may play a big role in the next generation of nuclear reactors. In May, TVA became the first utility to ask the Nuclear Regulatory Commission for a construction permit for a small, modular reactor in Oak Ridge. Prominent state Republicans, including Gov. Bill Lee and Sens. Marsha Blackburn and Bill Hagerty, have all pushed for a fast expansion of new nuclear plants in editorials this year.
