The nation’s largest federally owned utility received permission on Tuesday to build a new type of small nuclear reactor in Tennessee, in the latest sign of growing momentum for U.S. nuclear power.
The Tennessee Valley Authority was granted a construction permit by the Nuclear Regulatory Commission for a small reactor at its Clinch River site, west of Knoxville. It’s only the second time that U.S. regulators have given approval to build a next-generation commercial reactor. The first was in March for a project in Wyoming backed by Bill Gates.
“This construction permit is more than a regulatory achievement — it’s foundational for America’s nuclear future,” said Mike Skaggs, the T.V.A.’s interim president, in a statement.
The T.V.A. is considering up to four new reactors at Clinch River that are designed to be much smaller than traditional nuclear power plants. The hope is these “small modular reactors” will be easier to build and finance, potentially avoiding the delays and cost overruns that have plagued U.S. nuclear projects in recent decades.
Still, there are big hurdles. The T.V.A. hasn’t announced a construction date yet. And the utility has previously estimated that the first small reactor could be very expensive — potentially six times the cost of building a comparably sized gas-fired plant — though it expects costs to fall as it builds more and learn from experience.
Interest in nuclear energy has rebounded across the United States, particularly as demand for electricity grows amid a surge of A.I. data centers. The Trump administration wants to quadruple U.S. nuclear power by 2050, and even many Democrats have embraced the technology because it can run at all hours without emitting planet-warming greenhouse gases.
One big obstacle, however, has been the time and enormous expense to build new plants. The only two U.S. reactors built from scratch in recent decades, at the Vogtle nuclear power plant in Georgia, cost $35 billion, double initial estimates, and arrived seven years late.
Today, dozens of companies are betting that a new wave of smaller reactors could prove easier to construct.
The T.V.A. wants to use the BWRX-300, a small reactor designed by GE Vernova Hitachi Nuclear Energy. It’s technologically similar to most existing reactors but essentially shrunk down to 300 megawatts, about one-fourth the size of the reactors in Georgia. (That’s roughly enough to power 240,000 homes.)
A government-owned utility in Canada, Ontario Power Generation, is also planning a fleet of BWRX-300 reactors, and just installed the foundation for the first.
By working together on multiple plants in succession, the two utilities hope to drive down costs.
Another company, Blue Energy, applied this month for a permit to build the first in a series of BWRX-300s in Victoria, Texas, to power data centers. Blue Energy aims to mass-produce reactor components in factories to speed construction.
That isn’t the only approach.
TerraPower, a start-up founded by Mr. Gates, has designed a different type of small reactor cooled by sodium instead of water. It can ramp up and down to complement varying wind and solar power. The company received a construction permit in March and is building its first reactor in Kemmerer, Wyo.
Not far from Clinch River, at Oak Ridge National Laboratory, another start-up named Kairos is building a small 50 megawatt test reactor and is planning to sell power to the T.V.A. That reactor is cooled by molten fluoride salt, allowing it to operate at low pressures. The company has an agreement with Google to build more reactors to power data centers.
Other companies are building even tinier reactors to power military bases, some just 5 megawatts, with support from the U.S. Army.
The Trump administration also hasn’t ruled out building more giant reactors similar to those in Georgia, known as AP1000s, which use proven technology and can supply vast amounts of power. This year, the Energy Department offered $17.5 billion in loans to finance components for up to 10 new AP1000s. So far, however, no utilities have signed up.
Before any new reactor can be built, however, it needs a safety review from the Nuclear Regulatory Commission. In the past, some nuclear proponents had criticized the agency for being overly cautious and slow to act. In 2024, Congress passed a law to speed up nuclear reviews, and the Trump administration has pressured the commission to further streamline regulations . Other critics now worry the move could compromise safety.
Those changes appear to have had an effect. The commission reviewed T.V.A.’s construction permit application in just 14 months — four months ahead of schedule.
“Today’s Clinch River decision demonstrates that the new N.R.C. can make rigorous and credible safety decisions that enable major American nuclear projects to move forward,” said Ho Nieh, the commission’s chairman.
If the reactor gets built, its owners will still need to apply for a separate operating license before turning it on.
The T.V.A., which was created in 1933 as part of the New Deal, owns three nuclear power plants in Tennessee and Alabama. The last reactor it completed, Watts Bar Unit 2, came online in 2015 after nearly four decades of delays.
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