L.A.’s South Bay is emerging as a hub for the next generation of nuclear reactor development.
Three of the 11 projects in the U.S. Department of Energy’s reactor pilot program are from South Bay companies. Two of them, Radiant Industries Inc. and Valar Atomics Inc., are headquartered in El Segundo. The third, Antares Nuclear Inc., is just a dozen miles down the road in Torrance.
The DOE’s reactor pilot program was announced in June of last year as part of an initiative to speed the development of next-generation nuclear power in the United States by unlocking private funding and potentially fast-tracking future commercial licensing activities.
The first part has worked. Each of the three local companies has announced later-stage funding rounds exceeding $300 million since entering the program last summer, bringing the total raised by each company to $600 million or very close to it.
What’s more, Antares Nuclear and Valar Atomics achieved perhaps the most important milestone in the DOE reactor program: their reactors each achieved criticality before a July 4 deadline set by President Donald Trump’s administration. Criticality for a nuclear reactor is defined as the point at which a self-sustaining nuclear reaction is achieved. It does not mean that a nuclear reactor is generating net energy outflow. That’s generally the next step.
Antares Nuclear was the first in the program to achieve criticality on June 4, and Valar Atomics followed exactly two weeks later. Radiant Nuclear intends to achieve criticality later in its development process, likely by the end of this year.
Stephen Cheung, the chief executive of the Los Angeles County Economic Development Corp., hailed this development as a “promising early signal” of an advanced nuclear technology cluster in the South Bay.
“If these firms continue to scale, the opportunity for the broader L.A. economy is meaningful: high-skilled jobs, new supply-chain activity, private investment, and a stronger position for the region in next-generation energy and industrial innovation,” he said.
Going small
The other common theme among these three nuclear reactor developers is that they are all going small. Each nuclear reactor is packed into a container the size of a minibus and can be transported direct from the factory to the site. For more power, several of these microreactors can be assembled in a cluster.
Instead of massive nuclear fuel rods that can be up to 14 feet long, the nuclear fuel for this generation of reactors is contained in tiny kernels the size of poppy seeds wrapped in a protective ceramic and silicon carbide layer. Thousands of these covered nuclear pellets can then be put inside a larger heat-resistant graphite structure.
Antares Nuclear and Valar Atomics pack the pellets into something resembling a billiard ball, while Radiant Nuclear uses a solid graphite core block.
Each of the companies also say these smaller sizes make it easier to store nuclear waste in the short run, though none offered long-term solutions beyond a permanent repository that has yet to be implemented in the U.S. despite more than three decades of effort.
With these smaller sizes, the focus is on building in modular fashion, making hundreds and eventually thousands of these microreactors, to be used individually or as part of a cluster.
“This is aligned with the capital interest,” said Nana Menya Ayensu, a non-resident senior fellow and part of the nuclear energy policy initiative at the Washington D.C.-based Atlantic Council think tank. “Large reactors cost tens of billions of dollars, which is out of the realm of most venture capital. What’s more, this approach has the value of repetition, getting the cost cheaper with each batch of small reactors you make instead of a one-shot mega project.”
Ayensu added that there are niche markets that make sense for nuclear microreactors, such as in space, on military bases or in remote locatons.
Antares Nuclear: First to Criticality
The reactor developed by Redondo Beach-based Antares Nuclear Inc. was the first of the companies in the U.S. Department of Energy’s reactor pilot program to reach zero-power criticality, or the achievement of a self-sustaining nuclear reaction, though with no net electricity output. Valar Atomics reached a similar criticality milestone last November, but that was not through the Energy Department’s program.
Antares Nuclear reached that milestone on June 4 with its Mark-0 pilot reactor at the Idaho National Laboratory in Idaho Falls, Idaho.
Antares Nuclear was founded in 2023 by former Northrop Grumman Corp. engineering exec Jordan Bramble and former Space Exploration Technologies Corp. director Julia DeWahl.
Antares Nuclear has so far raised about $600 million, including $470 million in a series C funding round announced last week. That was led by Toronto-based Paradigm Capital Inc. and San Francisco-based Caffeinated Capital Management.
From the outset, the company targeted military and space applications for its microreactor. In an interview with the Business Journal in March, Bramble said that agencies such as the U.S. Department of Defense and NASA have long sought access to a reliable power source when few other options are available.
“The nuclear industry has spent decades optimizing for the commercial grid,” Bramble said in that interview. “Meanwhile, the customers who actually need and are willing to pay for nuclear power – the (Defense Department), NASA, remote industrial assets – were underprioritized. These customers, who need power that works for years in places where nothing else will, are who we founded the company to serve.”
In past decades, some of NASA’s unmanned probes destined for the outer planets – such as the Voyager and Galileo spacecraft – have had nuclear reactors on board. But that has been the extent of nuclear reactor deployment in space until now.
Like many of the other advanced microreactors now under development, Antares Nuclear’s reactor runs on tri-structural isotropic – or TRISO – fuel: uranium pellets covered by layers of carbon and ceramic that can contain nuclear fission byproducts at high temperatures. TRISO fuel does not require the massive domes to contain the heat that were common in Cold War-era nuclear reactors.
Because of a scarcity of uranium that meets the enrichment requirements for the reactor technology, Antares Nuclear earlier this year inked a supply deal with London-based uranium enrichment company Urenco Group.
For cooling, Antares Nuclear uses sodium-filled pipes to extract heat from the reactor core.
As for nuclear waste, Antares Nuclear said in an interview with the Business Journal that the used uranium pellets would remain inside the reactor for its entire operating life. “The volume is smaller than most people realize,” the statement said.
Deployment by 2028?
Next up for Antares Nuclear is the testing of the Mark 1, the company’s first full-power, electricity-generating microreactor. The company is aiming to test the Mark 1 sometime next year at the Idaho National Laboratory. The aim is to have a reactor life of at least six years without refueling.
After that, the company said it plans to ramp up production at its Torrance factory towards its goal of 10 microreactors per year. The first reactors could be deployed to customers in 2028.
The company noted that NASA has said it will need a fission reactor ready for deployment on the lunar surface as early as 2030. Furthermore, the Defense Department has set a target of 2031 for deployment of an in-space nuclear reactor.
“For 60 years, space nuclear was a research program,” the statement said. “It’s now a procurement pipeline and we’re building for it.”
Radiant Industries: Going the Full Prefab Route
El Segundo-based Radiant Industries Inc. was founded in 2020 by two former SpaceX engineers: Doug Bernauer and Bob Urberger.
It is the only one of the three companies that has yet to reach the criticality milestone. That’s because the company is taking a different tack, focusing on developing a fully functioning microreactor and running a series of tests to get the reactor ready for power generation.
Unlike some of the other companies, Radiant has put equal focus up front on building up its manufacturing plant in Oak Ridge, Tennessee, near the site of uranium enrichment facilities used for the Manhattan Project. Construction began last year on what the company touts as the first mass-production microreactor facility, capable of producing up to 50 microreactors per year. The aim is to have the first microreactor roll of the assembly line by 2028.
Once a reactor arrives at the customer site, it will simply be dropped into place, ready to produce electricity within 48 hours.
“It’s essentially energy in a box,” Bernauer, the company’s chief executive, said in comments provided to the Business Journal.
This two-track development process is possible because Radiant Nuclear has raised more than $575 million, including a series D round of “more than $300 million” announced last December.
Targeting commercial customers
Radiant Industries is targeting commercial markets, from data centers to industrial sites in remote locations. In many instances, the deployments are expected to be temporary, such as for contractors working in disaster response zones.
The microreactor, which Radiant Industries has named Kaleidos, will use the same type of uranium TRISO pellets that Antares and Valar use. But the cooling system will be different, using a combination of helium gas and air to whisk heat away from the core.
As for nuclear waste, Bernauer said it would remain entirely within the portable container, never seen or touched by the customer. Because many of the deployments are expected to be temporary, he said that when the deployment concludes, Radiant Industries would simply pick up the portable container and return it to the factory.
He added for longer deployments, when the uranium fuel runs low, Radiant Industries would pick up the reactor container and truck or fly it back to the factory, where it can be refueled and returned to the customer site.
Bernauer said that over the next two years, Radiant Industries will put its Kaleidos microreactor through a series of four test phases. That includes the zero-power criticality, a thermal test where energy is generated, a point-in-time full-power and heat test and finally, a duration test where the unit is fully powered for at least 150 consecutive hours.
He stressed that all these tests will be conducted on a unit that is identical to what is expected to roll off the production line at Oak Ridge.
“Every phase of this test validates the commercial product directly,” he said.
Valar Atomics: Seeking to Build Reactor Clusters
El Segundo-based Valar Atomics Inc.’s microreactor was the second in the DOE advanced nuclear reactor program to reach criticality back on June 18. The milestone occurred at the Utah San Rafael Energy Lab in Emery County southeast of Salt Lake City.
But it was not the first time Valar Atomics achieved what’s called zero-power criticality. That occurred back in November. But that was at Los Alamos National Laboratory in New Mexico under a different federal agency: the National Nuclear Security Administration.
In February, Valar Atomics garnered national attention when its microreactor modules were airlifted from California to the Utah San Rafael Energy Lab aboard U.S. Air Force C-17 cargo planes.
On June 21, Valar Atomics notched another milestone: bringing its microreactor to thermal power status at a level of 10 kilowatts for several hours overnight. Valar Atomics says this marked the first nuclear power-generated output by a startup.
And on July 1, Valar Atomics achieved yet another milestone: using electricity generated from its microreactor to power a Nvidia Corp. graphics processing unit with Blackwell microarchitecture design. Valar claims this is the first instance of electricity from an advanced nuclear reactor used to power AI infrastructure.
Valar Atomics’ Ward 250 microreactor uses TRISO-coated uranium pellets and a helium gas-based coolant system similar to Radiant Industries’ reactor. The pilot unit that achieved the milestones in recent weeks is licensed for 100 kilowatts standard output of up to 250 kilowatts. Valar Atomics intends for its commercial stage microreactor to generate up to 5 megawatts.
Mega clusters
But it’s the intended deployment of Valar Atomics’ reactor that distinguishes it from the other two local companies. It is seeking to deploy giant clusters of its microreactors.
“Valar is building America’s first nuclear gigasites – large-scale energy campuses powered by fleets of advanced reactors designed to deliver abundant, reliable power at unprecedented scale,” the company wrote in emailed responses to questions.
Co-founder and Chief Executive Isaiah Taylor elaborated on this in company comments following the June 18 criticality milestone. “Our mission at Valar Atomics is to make abundant energy for all mankind,” he said. “The best way to make energy 10 times cheaper today is to mass-scale nuclear fission.”
The company is targeting energy-intensive markets, such as data centers and other artificial intelligence infrastructure and defense applications.
Looking ahead, Valar Atomics intends to focus on honing its mass production of its microreactors. Each unit, the company said in its written responses, “will get built faster, cheaper and better.”
But Nana Menya Ayensu of the Atlantic Council had a cautionary note for this approach. “When it comes to hundreds of megawatts or even more, the jury is still out on whether hundreds of these smaller microreactors will be cheaper than the newest generation large reactors,” Ayensu said.
However, if the experience the last few years in Georgia is any indication, Valar Atomics will have quite a bit of room to maneuver on the cost front. Atlanta-based Georgia Power Co. in 2024 completed two new reactors at its Vogtle Electric Generation Plant near Waynesboro, Georgia with a cumulative maximum output of about 2,100 megawatts. The price tag: a staggering $36.8 billion over 15 years of construction for both new reactors, more than $20 billion over the original $14 billion estimate.
