Advanced Reactors

The drive to Kairos Power’s reactor demonstration site in Oak Ridge, Tenn., is not only scenic—it’s historic. Nearly 85 years ago, roughly 30,000 construction workers transformed orchards and farmland into a key Manhattan Project site. Depending on your route, you may pass by one of the three gatehouses that were once military checkpoints controlling access to Atomic Energy Commission production facilities.

On Thursday, Oklo announced that the Department of Energy’s Idaho Operations Office had approved the preliminary documented safety analysis (PDSA) for the company’s first deployment of its Aurora Powerhouse, which is currently under construction at Idaho National Laboratory.

It is the most recent in a long series of announcements from the 10 companies participating in the Reactor Pilot Program, which has a fast-approaching criticality deadline of July 4.

Leveraging more than $140 million in private capital fundraising, over 322,000 square feet of operational manufacturing space, and multifaceted partnerships with the Departments of Energy and Defense, reactor start-up Antares has become the first company involved in the Reactor Pilot Program to achieve zero-power fueled criticality—a full month ahead of the July 4 deadline set by President Trump’s Executive Order 14301.

This milestone, announced yesterday, was achieved with the company’s Mark-0, a forerunner to the R1, which is the company’s flagship design. The R1 is a sodium heat-pipe-cooled, TRISO-fueled microreactor. The Mark 0 is distinct from the R1 in that it is configured for zero-power criticality testing and as such is equipped with neither power conversion nor heat removal systems.

For Antares, this development represents a key validation of its reactor physics, control systems, and supply chain.

Washington, D.C. — Mark Peters, President of the American Nuclear Society (ANS), issued the following statement:

At the end of April, TerraPower announced that it had officially begun construction on its Natrium power plant in Kemmerer, Wyo.—one of the two full-scale demonstration projects in the Department of Energy’s Advanced Reactor Demonstration Program.

Now, the second ARDP-backed demonstration project, which aims to see the deployment of X-energy’s Xe-100 at a Dow chemical facility, has reached a new milestone of its own. On May 18, X-energy announced that the Nuclear Regulatory Commission has completed its environmental assessment of the proposed Long Mott Generating Facility and issued a finding of no significant impact (FONSI).

Indianapolis-based reactor development start-up First American Nuclear (FANCO) announced on May 13 that it has entered into a strategic alliance with Montreal-based nuclear engineering company AtkinsRéalis.

Together, the companies now plan to jointly develop, test, and license FANCO’s EAGL-1 reactor design. For FANCO, the agreement comes as a chance to bring in a partner with decades of experience in nuclear project development. For AtkinsRéalis, the partnership provides the opportunity to establish a presence in Indiana.

Today, commercial microreactors are common in the marketplace of nuclear ideas. Dozens of companies are vying for their designs to reach scaled deployment to meet surging energy demand.

However, the term “microreactor” didn’t appear in Nuclear News until 2019, when the Department of Defense popularized it (in a nuclear context) in the early days of what would become Project Pele. Even before then, however, all the way back in 2005, Toshiba was developing the 4S (Super-Safe, Small, and Simple), a 30-MWt, pool-type reactor designed for remote locations with small grids. Once sealed and delivered, the reactor would run for 30 years with no refueling. If the word “microreactor” had been in use then, the 4S would certainly have been categorized as such.

GE Vernova has formed a strategic collaboration with nuclear project financing and manufacturing firm Blue Energy to “advance the world’s first gas-plus-nuclear power plant.” The companies say that they intend to design and develop a power plant using GE Vernova Hitachi Nuclear Energy BWRX-300 small modular reactors and GE Vernova gas turbines to meet electricity demands related to AI and advanced manufacturing. Subject to a final investment decision in 2027, the first plant is to be located at a Blue Energy site in Texas and will power a nearby data center campus.

Admiral William Houston

As U.S. Navy submarines surface through Arctic ice during Ice Camp 2026, they demonstrate more than operational proficiency in one of the harshest environments on Earth. They reaffirm a technological truth first proven in August 1958, when the USS Nautilus completed its submerged transit of the North Pole: nuclear power enables access anywhere, anytime.

The Arctic is unforgiving, with vast distances, extreme cold, shifting ice, and no logistical infrastructure. Conventional propulsion is constrained by fuel, air, and endurance. Nuclear propulsion removes those constraints. Only a nuclear-powered submarine can operate anywhere in the world’s oceans, including under the polar ice, undetected and at maximum capability for extended periods. Nuclear power provides sustained high speed and the endurance to reposition across the globe without refueling.

Construction has officially begun on TerraPower’s first Natrium power plant, in Kemmerer, Wyo. The company expects this demonstration facility—featuring a 345-MWe sodium-cooled fast reactor with an integrated molten salt–based heat storage system, which can temporarily boost power output to 500 MWe—to become the first “utility-scale advanced nuclear power plant” in the United States.

On April 17, Kairos Power broke ground on its Hermes 2 demonstration plant in Oak Ridge, Tenn., for which it received test reactor construction permits from the Nuclear Regulatory Commission in November 2024. Kairos expects Hermes 2 to begin operations by 2030, when the fluoride salt–cooled high temperature reactor could become the first NRC-licensed non–light water reactor to produce power.

Indiana Gov. Mike Braun has signed a nonbinding letter of intent that will see the state’s Office of Energy Development (OED) and Indiana-based pharmaceutical company Eli Lilly collaborate to explore potential nuclear projects.

The focus of these projects—perhaps surprisingly—is not connected to medical radioisotope production. Rather, it will focus on “small modular reactors and other advanced nuclear technologies” that could provide “baseload power for industrial, research, and community uses,” according to the LOI.

Prime Minister Narendra Modi proclaimed it “a proud moment for India” when on April 6 the 500-MWe, sodium-cooled Prototype Fast Breeder Reactor (PFBR) achieved initial criticality. This milestone, which comes some 22 years after the continually delayed PFBR project began, marks India’s entrance into the second stage of its three-stage nuclear program, which has the ultimate goal of supporting the country’s nuclear power program with its significant thorium reserves.

On Wednesday, Idaho National Laboratory announced that the National Reactor Innovation Center’s Demonstration of Microreactor Experiments (DOME) test bed is now “open for business.”

With DOME’s opening, microreactor developers will soon be able to test, demonstrate, and validate their reactor designs. Rian Bahran, the Department of Energy’s deputy assistant secretary for nuclear reactors, called this “essential infrastructure” a “testament to our commitment to a robust nuclear future” and a key tool for “accelerating the development and deployment” of new energy technologies.

Valar's Ward250 microreactor being loaded, without fuel, onto a C-17 aircraft. (Photo: Valar Atomics)

A public-private partnership between the Departments of Defense and Energy and Valar Atomics marked a milestone over the weekend when Valar’s Ward250 microreactor was transported (without fuel) from California to Utah using three C-17 aircraft. The reactor will now trek from Hill Air Force Base to the Utah San Rafael Energy Lab (URSEL) for testing and evaluation.

A formal press conference at Hill Air Force Base included Energy Secretary Chris Wright, Undersecretary of Defense Michael Duffey, Utah Gov. Spencer Cox, and Valar Atomics CEO Isaiah Taylor.

During his remarks, Wright discussed the significance of the day, and said “a 5‑megawatt Valar Atomics nuclear reactor was just flown from L.A. to this air force base here in Utah—an incredible 5‑megawatt reactor that powers 5,000 homes, flown in the back of a plane.” The ability to transport microreactors like the Ward250 bolsters claims that the technology could be deployed to remote locations, military installations, or to support natural disaster relief missions.

An opportunity to request an adjudicatory hearing for Duke Energy Carolinas’ early site permit (ESP) application for the Belews Creek site in Stokes County, N.C., has been announced by the Nuclear Regulatory Commission. The notice of the opportunity was published February 9 in the Federal Register. The deadline to file a request for a hearing or petition for leave to intervene is April 10, 2026.

French advanced reactor developer Stellaria has formally submitted an application with the French government for authorization to build a prototype of its fast breeder molten salt reactor concept, known as Stellarium.

The company, which spun out of the country’s Alternative Energies and Atomic Energy Commission (CEA) and Schneider Electric, filed an application for authorization to create (DAC) for the reactor with the government minister in charge of nuclear safety, making it the first French start-up to submit an application with the authorities for a fast-neutron reactor.

Two participants in the Department of Energy’s Reactor Pilot Program have recently announced significant milestones on their associated reactor projects. Aalo Atomics successfully completed its final design review (FDR), and Antares Nuclear has received DOE approval of its preliminary documented safety analysis (PDSA).

Nuclear power in space is back in the news for the second time this week as microreactor start-up Nano Nuclear has released a request for information to identify organizations that may support the company in the development of its Loki micro modular reactor. The company’s goal is eventual deployment of Loki on the lunar surface.

Tech giant Meta is making big bets on TerraPower and Oklo. With the former, the hyperscaler could support the deployment of up to eight new reactors. With the latter, it could be as many as sixteen.

For both start-ups, Meta hopes its demand bolsters supply chains, the workforce, and the nuclear industry generally. For itself, the company is aiming to secure more generation to cleanly power its AI ambitions.