US-based Aalo has completed its Final Design Review (FDR) for its experimental reactor, Aalo-X, with independent reviewers from the Department of Energy (DOE) and the Nuclear Regulatory Commission (NRC). This follows completion of a Preliminary Design Review in October 2025.
The Aalo-X is an experimental, extra-modular reactor (XMR) that uses sodium as a coolant and is fuelled by low-enriched uranium dioxide. The Aalo-X is a full-scale, 10 MWe experimental power plant that bridges the gap between smaller microreactors and traditional small modular reactors (SMRs). The reactor and all its plant components are factory-built in modules for rapid on-site assembly.
In September 2025, Aalo and DOE executed an Other Transactional Agreement (OTA) enabling faster deployment of the Aalo-X shortly after Aalo broke ground for the reactor at Idaho National Laboratory (INL). This came just two weeks after Aalo was selected by DOE as one of ten companies 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 in line with Trump’s May 2025 Executive Order (EO) 14301, Reforming Nuclear Reactor Testing at the Department of Energy.
The FDR was a two-day, 16-hour review session involving 40 reviewers. Led by Co-founder and CTO Yasir Arafat, Aalo engineers gave presentations on the subsystems of the critical facility. The company also shared its plans for plant operations, security, and other administrative considerations necessary to run a nuclear facility.
Principal Mechatronics Engineer Austin Anthis noted: “We got thorough, constructive feedback from our reviewers. The feedback helps us iterate fast: it sharpens our design, improves our regulatory submittals, and builds confidence as we ramp up fabrication.”
The next step is to incorporate the reviewers’ feedback and submit a final Documented Safety Analysis & Readiness Assessment. Once approved, Aalo said it will have cleared all the regulatory hurdles necessary to achieve criticality “on a system that we designed, permitted, manufactured, installed at a building we constructed, and operated with our own operators. 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.
In his blog, Arafat offers virtually no information about the reactor itself referencing only a “sodium-cooled reactor”. However, all the earlier examples of reactors cited by Arafat are fast neutron reactors, indicating that this may be the intended design. The website also has no details. Fast reactors are complex facilities and going from conceptual design to criticality in two years seems ambitious.
