In a patch of high desert outside Kemmerer, Wyoming, construction crews are pouring concrete for a nuclear reactor unlike anything the United States has operated before. In Oak Ridge, Tennessee, another novel design is rising on land adjacent to the birthplace of the Manhattan Project. And at Idaho National Laboratory, a small company most Americans have never heard of is assembling a compact reactor it says could achieve a sustained chain reaction by Independence Day.
These three projects, led by TerraPower, Kairos Power, and Aalo Atomics, sit at the center of a federal push to demonstrate advanced nuclear technology on an aggressive timeline. The Department of Energy’s Reactor Pilot Program set a goal of reaching first criticality for at least three advanced reactor concepts outside national laboratories by July 4, 2026. If even one or two of these machines lights up on schedule, it would mark the first time in decades that an entirely new reactor design has gone critical on American soil.
The stakes extend well beyond symbolism. U.S. electricity demand is climbing at its fastest pace in a generation, driven by the explosive growth of data centers powering artificial intelligence, a resurgence in domestic manufacturing, and the electrification of transportation. The Trump administration has set a goal of quadrupling the nation’s nuclear generating capacity, and two executive orders issued in May 2025 reinforced that ambition: one streamlining nuclear reactor testing procedures at DOE facilities, another directing the deployment of advanced reactors for national security purposes. Together, they frame nuclear energy not just as climate policy but as industrial and defense strategy.
TerraPower: the strongest paperwork, the longest road
TerraPower, the company Bill Gates founded in 2008, holds the most significant regulatory milestone of the three. The Nuclear Regulatory Commission issued construction permit CPAR-1 for Kemmerer Power Station Unit 1 under Commission Order CLI-26-5, as documented in the NRC’s permit record. It is the first NRC construction permit ever granted for a sodium-cooled fast reactor, a design that can extract far more energy from uranium fuel than conventional light-water plants and can consume certain forms of nuclear waste as fuel.
But a construction permit is not an operating license. Kemmerer Unit 1 is a full-scale, 345-megawatt-electric power plant whose buildout will take years of fabrication, component testing, fuel delivery, and additional NRC review before it produces a single watt of electricity. Nothing in the permit record suggests the project is being treated as a rapid-turnaround testbed. TerraPower’s timeline extends well past 2026, making Kemmerer a cornerstone of the long-term nuclear expansion rather than a candidate for the July 4 sprint.
Kairos Power: permitted and building, but a year behind the target
Kairos Power’s Hermes reactor occupies a different niche. At 35 megawatts thermal, Hermes is a non-power demonstration unit designed to prove out a molten-fluoride-salt cooling technology that the company believes can be manufactured more cheaply and deployed more quickly than conventional reactor designs. The NRC granted Kairos a construction permit on December 14, 2023, and the company has since broken ground in Oak Ridge with funding from DOE’s Advanced Reactor Demonstration Program.
Hermes is the most advanced permitted non-power reactor in the country by NRC milestones. Yet DOE projects it will become operational in 2027, not 2026, placing it outside the Reactor Pilot Program’s first-wave deadline. Kairos has also filed a construction permit application for a follow-on Hermes 2 unit, which the NRC accepted for docketing, but neither the agency nor the company has confirmed an operational timeline for the second reactor in any primary document.
The 2027 projection for Hermes is perhaps the most telling data point for calibrating expectations across the entire program. If the furthest-along permitted test reactor in the country is running a year behind the headline deadline, the July 4, 2026 goal may function more as an aspirational benchmark than a hard operational milestone.
Aalo Atomics: the dark horse with the tightest deadline
Aalo Atomics, a startup far smaller and less well-known than its competitors, has moved fastest toward the 2026 target. The company executed an Other Transaction Agreement with DOE, completed a Preliminary Design Review for its Aalo-X reactor, and began construction activities at Idaho National Laboratory. Aalo has publicly stated it is targeting Aalo-X criticality by July 4, 2026, aligning its schedule directly with the Reactor Pilot Program’s stated goal.
Unlike Kemmerer or Hermes, Aalo-X is designed as a compact, non-power demonstration unit whose small scale and modular construction could, in principle, support a compressed timeline. But important caveats apply. An OTA is a real federal contracting mechanism, yet it is not equivalent to an NRC construction permit. A completed Preliminary Design Review does not guarantee that construction will finish on schedule or that the reactor will reach criticality by a specific date. And no corresponding DOE site-access documentation or independent safety review for Aalo-X construction at Idaho National Laboratory appears in publicly available federal records as of June 2026. Readers should treat the company’s deadline as a target, not a confirmed outcome. Slippage of months or even years is common in first-of-a-kind nuclear projects.
Oklo: ambition outpacing its regulatory position
Oklo, which drew public attention after its CEO served as an adviser to the Trump transition team, remains in pre-application interactions with the NRC for its Aurora Powerhouse design as of June 2026. No construction permit application has been submitted, and the NRC’s public materials list only pre-application white papers and topical reports under review. That phase is designed for early feedback on design choices and safety approaches, not for authorizing construction.
Notably, the NRC denied Oklo’s previous license application for a different version of its reactor in 2022, citing insufficient safety information. The company has since revised its approach, but the gap between public ambition and documented regulatory progress remains the widest of any company in this group. No published schedule from DOE or NRC suggests Aurora is being fast-tracked toward the 2026 window.
The bottlenecks no executive order can sign away
Political will is necessary but not sufficient. The May 2025 executive orders signal strong White House backing, but executive orders do not by themselves shorten NRC safety reviews, which operate under statutory mandates requiring detailed technical evaluations and public participation. No revised review timelines have been codified in available records, and regulators have not publicly stated how much practical speed the directives will add to licensing.
Fuel availability poses a quieter but equally serious constraint. Several advanced reactor designs, including TerraPower’s sodium-cooled fast reactor and multiple microreactor concepts, depend on high-assay low-enriched uranium, or HALEU, a fuel form that currently has extremely limited domestic production. The United States relied heavily on Russian-enriched HALEU until sanctions disrupted that supply chain. DOE has announced efforts to expand domestic HALEU capacity through contracts with Centrus Energy and other enrichers, but the timing and scale of that expansion relative to the 2026 criticality goal are not detailed in primary program documentation. A completed reactor structure without fuel cannot achieve first criticality.
Cost is another dimension largely absent from official timelines. TerraPower’s Kemmerer project alone carries an estimated price tag exceeding $4 billion, combining federal cost-share funding with private capital. Kairos and Aalo operate at smaller scales, but even demonstration reactors require hundreds of millions of dollars in sustained funding. Whether congressional appropriations and private investment will hold steady through potential political shifts remains an open question.
What a win actually looks like
No primary DOE or NRC record identifies which three specific projects among the 11 selected for the Reactor Pilot Program are on track to reach criticality by mid-2026 versus later dates. The program’s goal is stated in aggregate terms, and the gap between that goal and confirmed project schedules is significant.
But the significance of this moment does not hinge on whether the July 4 deadline is met to the day. The United States has not brought a genuinely new reactor concept from design to criticality outside a national laboratory in decades. China, by contrast, has already connected an advanced high-temperature gas-cooled reactor to its grid. Russia operates a sodium-cooled fast reactor commercially. The competitive pressure is real and growing.
Even reaching criticality with one or two smaller test reactors by the late 2020s would represent a major inflection point for the American nuclear industry. The NRC construction permits for Kemmerer and Hermes already carry binding legal weight, backed by completed safety and environmental reviews. These are not aspirational press releases; they are federal authorizations that clear the way for physical construction of reactor designs that existed only on paper a few years ago.
For now, the evidence supports a cautious but genuinely hopeful reading. The federal government has committed funding, executive attention, and early regulatory actions to an aggressive timeline. The documents with the greatest legal and technical weight, however, point to longer schedules and unresolved bottlenecks in fuel supply, licensing, and construction. The next year of permit filings, fuel contracts, and construction milestones will reveal whether this nuclear push can meet its own launch window or whether the real breakthrough arrives on a longer fuse. Either way, the concrete is being poured and the steel is going up. That alone separates this chapter from the decades of nuclear false starts that preceded it.
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*This article was researched with the help of AI, with human editors creating the final content.
