First Modular Nuclear Reactor Breaks Ground in Idaho

IDAHO FALLS, Idaho — U.S. startup Aalo Atomics has begun construction of the country’s first experimental extra modular nuclear reactor (XMR), a project that could redefine the role of advanced nuclear power in meeting America’s surging energy needs.

The new reactor, known as Aalo-X, is being built next to the Idaho National Laboratory’s Materials and Fuels Complex. Aalo expects the facility to be completed and reach operational criticality by July 4, 2026. Company leaders say the schedule underscores the rapid deployment potential of modular nuclear designs.

The project comes on the heels of the Department of Energy’s (DOE) decision to include Aalo in President Trump’s Nuclear Reactor Pilot Program, announced earlier this summer. The initiative is intended to accelerate testing and approval of next-generation nuclear technologies outside national labs, streamlining the path toward commercialization.

Founded in 2023 in Austin, Texas, Aalo Atomics has quickly risen to prominence in the nuclear startup space. Its leaders say the company’s progress is nothing short of groundbreaking.
“Our selection for the Nuclear Reactor Pilot Program is a significant catalyst for achieving our goal of going from ‘founding to fission’ in less than three years — a feat many deemed impossible just a year ago,” said Aalo Atomics cofounder and CEO Matt Loszak.

Backed by more than $136 million in private investment from Valor Equity Partners, NRG Energy, Hitachi Ventures, and others, Aalo is manufacturing the components for Aalo-X in a 40,000-square-foot pilot factory in Austin before transporting them to Idaho.

Once online, Aalo-X will mark the first sodium-cooled reactor to start in the U.S. in over four decades. Yasir Arafat, Aalo’s cofounder and CTO, emphasized its historic significance, noting his prior leadership on the DOE’s MARVEL reactor project.

Beyond its role as a demonstration plant, Aalo-X paves the way for the company’s Aalo Pod, a 50-megawatt modular power system designed for AI data centers. Each pod consists of five factory-built Aalo-1 reactors fueled by low-enriched uranium dioxide. Unlike traditional nuclear plants, Aalo’s modular systems do not require large external water supplies, making them scalable and adaptable for colocating at power-hungry data center sites.

John Wagner, director of the Idaho National Laboratory, called the construction a landmark for the nation’s energy landscape. “Today’s groundbreaking symbolizes the progress that can be achieved when innovation, vision and national purpose come together,” Wagner said.

With AI and data centers driving historic demand for electricity and policymakers under pressure to expand clean energy options, Aalo-X represents both a technological and regulatory breakthrough. If Aalo meets its timeline, the Idaho reactor could begin operations less than three years after the company’s founding — a pace virtually unprecedented in nuclear history.

Originally reported by Neetika Walter in Interesting Engineering.