Advanced Reactors

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.

This week, the Department of Energy has finalized two new other transaction agreements (OTAs) with participating companies in its Reactor Pilot Program, which aims to get one or two fast-tracked reactors on line by July 4 of this year. Those companies are Terrestrial Energy and Oklo.

New York City–based Nano Nuclear Energy has signed a memorandum of understanding with the University of Illinois Board of Trustees, on behalf of the University of Illinois–Urbana-Champaign, to collaborate on the development, construction, and operation of the company’s Kronos MMR (micro modular reactor) as an on-campus research reactor. The new MOU represents the latest aspect of Nano Nuclear’s partnership on the Kronos MMR project with the university, which includes state funding for a manufacturing and research center, to be located in the Chicago suburb of Oak Brook.

Following up on an October announcement on plans to invest more heavily in nuclear power, Duke Energy closed out 2025 by submitting an early site permit application to the Nuclear Regulatory Commission. This ESP application is for a site near the Belews Creek Steam Station, a coal and natural gas plant in Stokes County, N.C., where Duke has been pursuing a new nuclear project for two years.

Progress in the Department of Energy’s Reactor Pilot Program continues as Natura Resources has executed an Other Transaction Agreement (OTA) with the DOE for the company’s Molten Salt Research Reactor being pursued in close collaboration with Abilene Christian University (ACU) in Texas. Reactor projects participating in the program would progress through DOE authorization and oversight rather than Nuclear Regulatory Commission licensing.

GE Vernova Hitachi Nuclear Energy’s BWRX-300 small modular reactor has completed the second step of the generic design assessment (GDA) process in the United Kingdom. In this step, the U.K. Office for Nuclear Regulation, the Environment Agency, and Natural Resources Wales did not identify “any fundamental safety, security safeguard or environmental protection shortfalls with the design of the BWRX-300.” Step 1 was completed in December 2024.

With about seven months left in the race to bring DOE-authorized test reactors on line by July 4, 2026, via the Reactor Pilot Program, Deep Fission has announced that it will break ground on its associated project on December 9 in Parsons, Kansas. It’s one of many companies in the program that has made significant headway in recent months.