Nuclear Notes is produced by the Breakthrough Institute, and covers the policy, regulation, technology, and business of advanced nuclear energy in the United States and beyond.
Every Thursday, we track what’s really going on in the field: the new rules moving through the Nuclear Regulatory Commission, the advanced reactors moving from design to deployment, the companies going public and the utilities merging, and the executive orders and acts of Congress reshaping how the country builds. We explain not just what happened, but why it matters and how the pieces fit together.
How Does Nuclear Caution Mesh with High-Tech Urgency?
Much of the impetus for new nuclear construction, and some of the money for advanced nuclear designs, comes from high-tech Silicon Valley firms that need electricity and want to bring their culture of fast innovation to an industry with big potential but a high degree of inertia.
In an insightful blogpost, José N. Reyes, the co-founder of NuScale Power, points out that this could be a helpful infusion of resources and skills, or it could be a collision.
There are big differences between the “move-fast-and-break-things” school of business management and the more cautious approach of the nuclear industry.
“Tech companies typically build simple versions of products, iterating and perfecting them over time,” Reyes wrote. “You simply cannot release a ‘beta version’ of a commercial nuclear reactor, hoping to fix bugs as they arise in real time.”
And he cited a recent comment by the Nuclear Regulatory Commission’s Advisory Committee on Reactor Safeguards, which reviews all license applications, stating that some reports submitted to the Commission by reactor developers lack the technical detail needed for evaluation. The Committee’s comments conveyed that rushed applications may seem to demonstrate progress toward licensing but they waste NRC resources.
Reyes pointed out that tech companies often use a “fail fast” strategy, trying out ideas promptly to see if they will work. “This approach may be suitable for a test reactor in a highly controlled laboratory environment, however the subsequent transition from test reactor to commercial nuclear plant still requires an in-depth NRC safety review and licensing process,” he wrote.
Which culture will prevail?
NuScale may have a different outlook on the licensing process since it has been through it and, after great effort and expense, has a licensed design. At the other end of the spectrum is Oklo, a Silicon Valley start-up, which applied for a license in March 2020 but saw the NRC reject it and cease its evaluation in January 2022 because, the regulator said, the application was not complete enough. Oklo is trying again.
And Last Energy, Deep Fission, and Valar Atomics are trying to get past the NRC licensing process and move forward fast by suing the NRC and challenging its jurisdiction.
Kairos Power is taking a different tack, adopting an approach similar to that of Space-X–building, testing, learning, and starting over with the lessons learned. But Kairos is doing that with components and small test reactors, not the finished product.
All these companies are a stark contrast to the ones that designed the power reactors now in use in the United States. All were long-standing pillars of the energy industry, with extensive experience in coal and natural gas, and were modifying the design of those plants to take advantage of a new heat source. They were using a familiar material, ordinary water, and already had experience with many of the pumps, valves and instruments that their plants would need. Today’s designers are starting with a clean sheet, using molten salt or metal in some cases, and have little background in manufacturing.
And in the first round of nuclear construction, the heavy equipment companies—Westinghouse, General Electric, Combustion Engineering, and Babcock & Wilcox—were selling to utilities, which are technologically conservative. Today the customers include tech companies, hyperscalers, a chemical company that wants steam rather than electricity, and, potentially, a variety of enterprises that want close-at-hand, reliable generators to power their operations.
The Electric Power Research Institute, a non-profit utility consortium, captured some of the culture clash in an article describing a meeting in London of the Global Forum for Nuclear Innovation. Rather than engineering presentations, the event began with a hip stage performance by Jon Chase, who defines his specialty as “rapscience.”
He sang, “so, on the one hand, there is safety. On the other is innovation. One relies on caution and the other inspiration, but the two must function hand in hand for any operation to succeed.”
Four for the Fourth
Aalo Atomics’ Critical Test Reactor reached initial criticality a few minutes after midnight on July 4 at the Idaho National Laboratory, and is the fourth advanced reactor to meet that deadline, set by an executive order fourteen months ago. The company said it demonstrated the nuclear components of a 10-MW reactor (although not other parts of the system).
“Criticality has validated our supply chain, reactor physics, control systems, and fueling procedures at commercial scale,” the company said in an announcement, noting that it had gone from groundbreaking to initial criticality in less than eight months.
President Trump’s Executive Order 14301, “Reforming Nuclear Reactor Testing at the Department of Energy,” signed in May of 2025, called for at least three initial criticalities by independence day of this year.
All four are micro-reactors, producing power at levels similar to a large diesel generator.
Antares Nuclear’s reactor, Mark-0, achieved criticality in June, under the Department of Energy’s Reactor Pilot Program. Antares credited support from the U.S. Army, and says it will deploy on military bases in 2028. It is meant to be delivered by truck, and can be shut down and moved to another location if needed.
Valar Atomic’s Ward 250 reactor also sustained a criticality in June, at a laboratory in Utah. It has a capacity of 5 megawatts and is intended to be transportable.
Valar reached the same milestone with a different core design last November.
A third company, Deployable Energy, announced on July 1 that its one-megawatt Unity reactor had achieved initial criticality. It was part of a separate Energy Department program, the Nuclear Energy Launch Pad initiative.
Initial criticality, sometimes referred to as zero-power criticality, means that a core has achieved a self-sustaining chain reaction, usually at a power level of a few hundred watts or a few kilowatts. It produces data that can help a company apply for a license from the Nuclear Regulatory Commission, which it will need for commercial deployment. All four got test authorization for initial criticality from the Department of Energy, which is easier than getting commercial permission from the NRC.
To be a commercial product, a reactor would also need a system for converting the heat to electricity. In the case of these small reactors, the developers would also need to be able to produce many copies. Microreactors are something of a niche product, intended for places that have a high need for reliability, or are located far from the grid, often in places where delivery of diesel fuel is difficult.
Vogtle 4 Becomes an Industry Standard
The Nuclear Regulatory Commission has agreed to review an application by Westinghouse to amend the design certification for the AP1000 to match Georgia Power’s Vogtle 4 reactor. This would essentially absorb Vogtle 4 specifications, amendments, and changes into the January 2006 AP1000 design approval, and ameliorate a problem with the Part 52 licensing procedure under which the plant was built: Every deviation from the pre-approved design required a license amendment. By making Vogtle 4 the standard, future AP1000s will presumably require very few amendments. The only foreseeable variations would be for local geology and other site-specific considerations.
Previous NRC regulations, conceived before this problem became obvious in Vogtle’s construction, would have frozen the certification until 2043. The NRC gave the company a one-time exemption to allow it to apply for the revision now. Westinghouse hopes that the regulators will approve the updated certified design later this year. That could slightly simplify the task envisioned by the Trump administration: getting five twin-unit AP1000 plants under construction.
Report: Global Nuclear Market Will Be Strong, and Russia Will Benefit
Globally, the prospects are good for a major expansion of nuclear energy, according to the Nuclear Energy Agency, but among planned and proposed projects around the world using imported technology, Russian VVER design dominates, comprising 40 percent of all internationally procured reactors. And more than half of Russia’s nuclear industry is manufacturing units for export.
The Nuclear Energy Agency, part of the Organisation for Economic Co-operation and Development, gives only passing mention to reactor technology beyond light water, the type that now dominates, and says that small modular reactors will not enter the market until the mid-2040s, and in only a modest way, even under the most optimistic scenario. And tripling nuclear capacity by mid-century would take a transformative effort, the report said.
Russia’s war against Ukraine, which made Europe’s largest nuclear plant, Zaporizhzhia, an intermittent target, has sharpened the appetite of governments for nuclear energy, the report said, because reactors substitute for fossil fuel imports.
Two More Nuclear Companies Head to Wall Street
The Canadian firm that owns the rights to that country’s pressurized heavy water reactor technology has notified the NRC that it will apply for a license in the U.S.
The CANDU reactor (for Canada Deuterium Uranium) runs on unenriched uranium and heavy water. Few have been built recently, but several have been refurbished. AtkinsRéalis, an engineering and project management company, will seek to market a 700-megawatt version in the U.S. The move comes as an American/Japanese design, the GE Vernova Hitachi BWRX-300, is under construction in Ontario.
In addition to Canada, CANDUs operate in South Korea, China, Argentina, Romania and India. Canada recently committed itself to developing a national nuclear energy strategy and expanding export markets.
Thanks for reading!