Why Aalo Chose Sodium

Aalo chose sodium as its reactor coolant because of its superior thermal performance, low operating pressure, and inherent passive safety characteristics. Sodium can transfer heat more efficiently than water or gas coolants, enabling compact reactor cores with high power densities. Unlike pressurized water reactors, sodium systems operate at atmospheric pressure, eliminating the need for expensive pressure vessels and reducing the risk of explosive failures. These attributes make sodium uniquely suited to Aalo’s goals of delivering modular, high-efficiency microreactors that can be factory-built and rapidly deployed to sites with limited space and infrastructure.

The Challenge of Sodium Reactors

Sodium is a highly promising coolant with unique advantages, but it has not yet been commercialized at scale due to a range of technical challenges. Despite more than 800 reactor-years of global sodium reactor experience across projects like FFTF, EBR-II, SRE, Hallam, Clinch River, and KNK I & II, there are still significant gaps in operational knowledge, especially in areas such as sodium purity management, leak detection, and materials behavior. To successfully commercialize Aalo-1, Aalo must demonstrate mastery over sodium reactor construction and operation—including thermal hydraulics, maintenance, refueling, and system reliability. Aalo-X gives us a unique opportunity to do this hands-on, taking direct lessons from historical sodium programs and applying them in a modern, manufacturable design context.

De-Risking Aalo-1

Aalo-X is the proving ground for all critical systems that will ultimately be licensed under the NRC for Aalo-1. Building and operating Aalo-X under DOE authorization allows Aalo to move from design to operation faster than any other advanced reactor company. This early operational experience allows us to fine-tune our systems, validate our manufacturing and construction approach, and optimize our reactor’s behavior under real-world conditions. As a result, Aalo is establishing itself as the global leader in sodium-cooled reactor deployment, positioned to deliver rapid, cost-effective, and scalable nuclear energy solutions, particularly for mission-critical applications like data centers.

Pursuing DOE authorization for Aalo-X gives Aalo a significant speed advantage over traditional NRC licensing. Under DOE-STD-1189’s in situ review process, first-of-a-kind (FOAK) experimental reactors can benefit from accelerated review timelines, enabling construction and testing to begin much earlier. The DOE does not charge private entities for licensing, making it a more cost-effective path. Aalo’s leadership team brings deep experience in this framework, successfully leading the MARVEL reactor project under DOE authorization. This familiarity with regulatory personnel and the process gives us a clear execution advantage. Furthermore, the DOE framework is inherently more flexible—it allows design evolution during construction, testing, and early startup without triggering long delays or formal public hearings that would typically occur under the NRC process. This flexibility is essential for innovation and rapid iteration as we develop the most advanced sodium reactor ever built in the United States.