Austin-based Aalo Atomics has broken ground for its Aalo-X experimental extra modular nuclear reactor (XMR) at Idaho National Laboratory (INL), next to INL’s Materials & Fuels Complex. This came just two weeks after Aalo was selected by the US Department of Energy (DOE) to participate in President Trump’s Nuclear Reactor Pilot Program.
Aalo is intending to complete construction of Aalo-X and achieve criticality by July 2026. This is in line with Executive Order (EO) 14301, Reforming Nuclear Reactor Testing at the Department of Energy signed by President Trump in May to fast-track nuclear development. The EO stated that a Pilot Program will be established under DOE control outside the National Laboratories. “The Energy Secretary will approve at least three reactors for this programme with the goal of achieving criticality of each by 4 July 2026. The Secretary will assign a team to provide assistance to the applicant.”
“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 Matt Loszak, Aalo Co-founder & CEO. “This milestone groundbreaking event is a testament to the potential that can be unlocked when public entities and private companies partner together in the critical interest of the nation. This is a pivotal time for the U.S. nuclear energy industry, and we are incredibly proud to be at the forefront.”
DOE formally announced the Reactor Pilot Program in June 2025 to expedite the testing of advanced reactor designs as a step toward streamlining nuclear reactor testing providing a new pathway toward fast-tracking commercial licensing activities. Aalo was selected for the program following a competitive Request for Applications (RFA) process and aims to be the first recipient to begin construction on a test facility.
“At Idaho National Laboratory, we are proud to support the Department of Energy’s efforts to accelerate advanced nuclear technologies that strengthen America’s energy security, provide reliable power, and inspire the next generation of innovators,” said INL Director John Wagner. Projects like Aalo-X reflect the promise of nuclear energy to meet our nation’s historic demand growth and help enable a more prosperous future for our nation.”
Aalo-X will be manufactured at Aalo’s 40,000 square foot pilot factory in Austin, Texas, before being transported to and installed at INL. “When Aalo-X achieves criticality next year, it will become the first new sodium-cooled reactor to start operation in the US in over four decades,” said Yasir Arafat, Cofounder and CTO at Aalo Atomics, who previously led the MARVEL project at INL. “Aalo-X is just the beginning as we are poised to deploy nuclear power on a scale that far exceeds the first atomic age.”
In April, Aalo announced the Aalo Pod – a 50 MWe XMR, purpose-built to provide scalable on-site power for modern data centres. The Aalo Pod is built around 50 MW modular blocks, easily scalable up to gigawatt levels with a compact footprint – 100 MW on less than five acres. Each standard Pod comprises five Aalo-1 reactors paired with a single power-generating turbine. The Aalo Pod is expected to provide commercial power in 2029.
Aalo says: “The Aalo-X comprises the same reactor that goes in each of the Aalo-pods, except it is a single reactor, connected to a 10 MWe turbine. As we prove Aalo-X, we also prove the entire life cycle of the Aalo Pod, from design, safety basis, procurement, manufacturing, installation and interfacing, operation, refuelling, to decommissioning.”
Aalo‑X “looks like a commercial building because it is”, Arafat said in an update on the company website. “In legacy reactors, the containment and safety systems are huge concrete structures, costing $3,000–6,000 per square foot and taking years to build. Our team miniaturised every safety‑related civil structure (e.g. containment, shielding, etc) into equipment modules (including the containment and shielding) with a small volume that wraps around the reactor itself. The result is significantly less steel and concrete per MWe than most traditional designs. Therefore, the building superstructure is nothing but a frame and metal‑panel building that can be erected by the same crews that build warehouses and data centres.”
He added: “Because over 90 % of the plant is manufactured in factories, the on‑site work is limited to months, not years. This approach slashes capital costs, reduces risk, and allows us to replicate plants rapidly. By turning the “nuclear building” into ordinary infrastructure, we intend to make nuclear power competitive with natural gas.”
Arafat said breaking ground on Aalo‑X demonstrates that with the right design philosophy – being obsessed with modularity, factory manufacturability, and rapid iterative learning – we can compress timelines from decades to years. “Within months, we will have assembled the first XMR at our Idaho site; by July 4, 2026, we will reach criticality, and by July 2027, we will power a collocated data centre, with next-generation AI chips. Once operational, Aalo‑X will be a tangible proof‑of‑concept that nuclear energy can power the AI revolution rapidly and cost‑effectively.”
In a subsequent update, Arafat explains at length the work that has been done on the liquid sodium coolant, noting problems that had occurred as a result of sodium leaks in early Russian sodium-cooled fast reactors, France’s Phénix and Japan’s Monju. The secondary sodium leak at Monju in 1995 resulted in a 15-year shutdown.
“Our team recognised from the outset that solving these core issues, sodium purity, sodium-water isolation, and pumping, is fundamental to any viable sodium reactor. We could not simply assume off-the-shelf solutions existed. In fact, we found that no commercial vendors offered ready-made cold traps or double-walled steam generators for sodium, and that existing pump designs needed modernisation.”
He continued: We decided from day one to build and test our own high-performance cold traps, duplex steam generators, robust pumps, and, uniquely, an autonomous maintenance robot. These four systems, built in-house with trusted partners, form the backbone of a reliable plant. Developing these technologies… is only the beginning. The next crucial step is integrated testing. We have constructed a dedicated sodium test loop at our pilot facility to assemble and try out all these components working together. Learning from the sodium test loop will enable us to operate another integral test loop, the Aalo-0, which is a full-scale non-nuclear prototype of the reactor. We can circulate hot sodium, capture oxygen with our cold trap, and generate steam via a small section of double-wall heat exchanger, all while monitoring performance, control systems, and safety instrumentation.”
He added that “the data and lessons learned from our pilot technologies are being fed back into our reactor design”. However, there is virtually no information about the reactor itself, referencing only a “sodium-cooled reactor”. Given that all the earlier examples cited in the update are fast neutron reactors, it seems that may be the intended design. In May 2024, Aalo said it had completed the conceptual design of the Aalo-1, but gave no detail, and the Aalo website says nothing about the reactor technology. Fast reactors are complex facilities and going from conceptual design to criticality in two years seems unlikely.
