US starts building first experimental modular nuclear reactor

Aalo Atomics, a U.S. startup founded in 2023 and based in Austin, Texas, has begun construction on Aalo-X, the nation’s first experimental extra modular nuclear reactor (XMR). Located near the Idaho National Laboratory’s Materials and Fuels Complex, Aalo-X is the first sodium-cooled reactor built in the U.S. in over 40 years. The company aims to complete construction and achieve criticality by July 4, 2026, demonstrating the rapid deployment potential of small modular reactors. This project is part of the Department of Energy’s Nuclear Reactor Pilot Program, launched in June 2025 to accelerate testing and approval of advanced nuclear designs outside national labs, facilitating faster commercial deployment. Aalo Atomics is positioning its technology to meet the surging energy demands driven by artificial intelligence and data centers. The Aalo-X reactor serves as a precursor to the Aalo Pod, a scalable 50-megawatt modular power plant designed specifically for data centers