Deadline vs. Deployment: Can U.S. Advanced Reactors Meet DOE’s 2026 Criticality Goal?

In a new pilot program, the U.S. Department of Energy (DOE) issued an ambitious challenge: bring at least three advanced nuclear test reactors to criticality by July 4, 2026. Announced in June, the program sidesteps traditional Nuclear Regulatory Commission (NRC) licensing, seeking instead to authorize full-scale reactors on private sites through DOE’s internal review process. While the initiative could serve as a proving ground for novel designs, it also raises questions. A crucial emerging concern is that the DOE’s pilot program deadline to achieve criticality—just 13 months away—represents an aggressive timeline.

As detailed in POWER’s June 25 story, “DOE Pilot Program Targets Three Nuclear Test Reactors for 2026 Criticality Under Department Authorization,” the pilot program is rooted in a Trump-era executive order and relies on DOE’s authority under the Atomic Energy Act. According to a Request for Applications (RFA) issued by the DOE, submitters must demonstrate a mature reactor design, a qualified fuel and waste disposition plan, full execution readiness, and sufficient financial and supply chain resources, with submissions for initial projects due by July 21, 2025.

And while the DOE said it will consider only “qualified test reactors capable of demonstrating the ability to achieve criticality safely by the target date of July 4, 2026, or as soon as possible thereafter,” the term “Qualified Test Reactor” refers to a nuclear fission reactor that offers substantial improvements over those operating as of Dec. 27, 2020—including enhanced safety, lower waste, improved fuel performance, greater efficiency, modularity, and the flexibility to support both electric and non-electric applications.

At least for now, according to the Nuclear Innovation Alliance’s latest update (June 2025) of its Advanced Reactor Timeline, a handful of projects could meet the 2026 timeframe, though even the most mature projects in the U.S. are tracking toward operations later in the decade.

So far, “Reactor developers are already engaging with customers, local and state governments, and the [NRC] to secure the regulatory approvals necessary for construction, commissioning, and operation,” the group notes. “These first-mover projects will provide the licensing, construction, and operational experience that enable rapid commercial deployment of advanced nuclear energy in the 2030s.” More rapid progress could come thereafter, it suggests. “Technology, business, and regulatory lessons learned from first-of-a-kind (FOAK) projects and demonstration reactors will facilitate lower costs and shorter construction timelines for subsequent nth-of-a-kind (NOAK) reactors due to wide-scale deployment and technological learning. Utilities and other customers that gain early experience with FOAK or early NOAK projects will be in competitive positions to become technology leaders.”

Explore the Global Nuclear RevivalFor a deeper dive into the policy breakthroughs, market drivers, and international competition shaping nuclear’s future, read POWER magazine’s special report published in November 2024: Can Nuclear’s Big Recent Wins Propel a True Global Revival? The feature examines how recent U.S. and global milestones—from new project announcements and financing models to regulatory reforms—are converging to accelerate nuclear deployment worldwide. But it also offers analysis on supply chain realities, technology innovation, and the challenges that must still be overcome for a true nuclear renaissance.

Demonstration Non-LWRs

Under the DOE’s Advanced Reactor Demonstration Program (ARDP), notable progress has been made by X-energy and TerraPower in advancing their non-light-water reactor projects. X-energy has secured a cost-share award to construct four Xe-100 high-temperature gas-cooled reactors at Dow Chemical’s Seadrift site in Texas, seeking to support industrial decarbonization efforts for the Long Mott Energy project. As of mid-2025, the project is in the pre-construction phase, with site preparations underway. In June, the NRC published an 18-month review timeline for the Texas project and indicated it would proceed with its environmental assessment. X-energy CEO Clay Sell recently suggested the project’s earliest commercial operation date will likely be “in the early 2030s.”

Meanwhile, TerraPower’s Natrium reactor—a sodium fast reactor paired with a molten salt energy storage system—is progressing at the former Naughton coal plant site in Kemmerer, Wyoming. The project has completed site characterization and received a state construction permit in January 2025. TerraPower submitted its construction permit application to the NRC in March 2024. COO Eric Williams told POWER in June 2025 that the NRC’s review is “ahead of schedule,” with potential approval expected before the end of 2026. While the company pushed its operational target to 2030 due to HALEU fuel supply delays, early construction work is already underway, including the Test and Fill Facility and the Kemmerer Training Center. “We’re basically under procurement now for the nuclear island,” Williams said, adding that long-lead materials for the reactor vessel head will be ordered “in a couple of weeks.” Detailed engineering is in its final stages, with more than 1,000 people actively working on the project alongside major partners Bechtel and GE Hitachi. Williams expressed optimism about the pace of progress:“So, that’s pretty exciting,” he said. “That construction permit application allows us to begin construction on the nuclear side of the plant, but we can really start construction on the non-nuclear side of the plant anytime.”

Commercial Small Modular LWRs

In the realm of small modular light-water reactors (SMRs), GE-Hitachi has made significant strides with its BWRX-300 design, announcing partnerships with the Tennessee Valley Authority (TVA) and Ontario Power Generation (OPG). In May 2025, Ontario’s regulator approved construction at the Darlington site, and it indicated site preparation is already well underway, and the first concrete is expected later this year. OPG anticipates, pending regulatory approval, that the first unit could commence operations by the end of 2029. Projected in-service dates for the three additional SMRs are in the mid-2030s, between 2034 and 2036. TVA has submitted its construction permit application for the Clinch River site in Tennessee, with deployment anticipated in the latter half of the decade.

Holtec International has also advanced plans to deploy its SMR-300 reactor at the Palisades Nuclear Power Plant in Michigan, alongside the existing large LWR, with the company launching its “Mission 2030” initiative to accelerate licensing and deployment. The project is in early licensing stages, with the goal of achieving commercial operation by the early 2030s.

Demonstration and Test Microreactors

The DOE’s aggressive timeframe will more likely be met by the burgeoning nuclear microreactor sector, which has seen remarkable activity, with several projects nearing operational readiness. Oklo and Aalo Atomics have both announced plans to construct and operate commercial demonstration microreactors at INL in Idaho. Oklo’s Aurora microreactor is progressing toward a combined license application planned for late 2025, with NRC licensing and site characterization efforts underway, and it has said the reactor remains on track for operation in 2027. Aalo Atomics’s first reactor, Aalo-X, is set to begin construction at INL in 2026 and “go critical in 2027 under a DOE authorization pathway,” INL’s GAIN said in a June 2025–updated report. “In parallel, Aalo is pursuing NRC licensing for future commercial deployment.”

The BWXT-designed Project Pele, a transportable microreactor for the U.S. Department of Defense, is also reportedly on track for reactor fuel loading and demonstration at INL in 2026, following assembly that began in February 2025. Meanwhile, Kairos Power has already started construction of its Hermes Low-Power Demonstration Reactor, near Oak Ridge, Tennessee. Hermes is a 35-MWth iterative non-power demonstration molten salt nuclear reactor of Kairos Power’s fluoride salt-cooled high-temperature reactor technology and became the first advanced nuclear reactor to receive a construction permit from NRC. Its completion is anticipated in 2027.

In tandem, Shepherd Power, in partnership with BWXT, plans to deploy the BANR microreactor in West Texas to support oil and gas operations, with initial demonstrations expected later this decade. “While the first commercial units are expected to be available by the early 2030s, we are actively working to clear regulatory hurdles, develop deployment pathways, and align supply chains to make advanced reactors a turnkey energy solution when the technology is ready,” the company notes on its website.

University Research Microreactors

Academic and research microreactors are also making progress. As part of its state-backed “Energy Proving Ground” initiative, the Texas A&M University System is moving forward with siting and licensing multiple SMRs at its RELLIS Campus. The university selected Kairos Power, Terrestrial Energy, Natura Resources, and Aalo Atomics to assess and license advanced reactor technologies, including molten salt and microreactor designs. Texas A&M has initiated an Early Site Permit process with the NRC and seeks to support development of multiple units—totaling between 10 MW and 1 GW—for grid-connected commercial use as early as the 2030s.

Meanwhile, NANO Nuclear, partnering with the University of Illinois at Urbana-Champaign, signed a formal agreement in April 2025 to site and license the first KRONOS micro modular reactor (MMR) on the university’s campus. The stationary high-temperature gas microreactor—based on USNC-derived technology—will serve as a full-scale research and demonstration unit. The collaboration has entered the pre-application phase with the NRC, and subsurface site investigations are underway to support a construction permit application and accompanying safety and environmental reports.

Separately, NEXT Lab and Natura Resources are collaborating with Abilene Christian University on a molten salt research reactor, with construction of supporting facilities underway and licensing efforts ongoing. Natura aims to deploy its 100-MWe commercial Natura MSR-100 system by 2030.

Finally, Westinghouse in March 2025 revealed it has partnered with Penn State University to develop and deploy the eVinci microreactor, focusing on rapid prototyping, testing, and educational applications. Penn State submitted a letter of intent to the Nuclear Regulatory Commission in February 2025, initiating the application process for installing Westinghouse’s eVinci microreactor at University Park as part of the FRONTIER (Forging a Renaissance of Nuclear Through Innovation, Entrepreneurship, and Research) initiative. The collaboration builds on Penn State’s nuclear legacy, including operation of the Breazeale Reactor since 1955—the first licensed research reactor in the U.S.—which will continue operating alongside the potential eVinci deployment.

—Sonal Patel is a POWER senior editor (@sonalcpatel, @POWERmagazine).