Small modular reactors represent the most significant shift in nuclear power plant design since the industry's inception. Defined by the International Atomic Energy Agency (IAEA) as reactors producing less than 300 MWe of electrical output, SMRs are engineered for factory fabrication and modular on-site assembly, fundamentally altering the construction economics that have plagued conventional large-scale nuclear projects. Unlike traditional gigawatt-class plants that require decade-long, bespoke construction campaigns, SMR modules can be manufactured on assembly lines, transported by truck or rail, and installed incrementally to match demand growth.
The SMR landscape spans multiple coolant technologies and design philosophies. Light-water designs from NuScale Power (VOYGR, 77 MWe per module), GE-Hitachi (BWRX-300, 300 MWe), Rolls-Royce SMR (470 MWe), and Holtec International (SMR-300, 300 MWe) leverage decades of pressurized and boiling water reactor operating experience. Advanced designs push beyond water cooling: TerraPower's Natrium uses liquid sodium to achieve 345 MWe baseload with 500 MWe peak output via integrated molten salt energy storage, while X-energy's Xe-100 employs helium coolant and TRISO pebble fuel to reach outlet temperatures exceeding 750 degrees Celsius for industrial process heat applications. Kairos Power's KP-FHR uses fluoride salt coolant with TRISO fuel, and Oklo's Aurora is a compact sodium-cooled fast reactor targeting 15-75 MWe.
As of early 2026, China's Linglong One (ACP100) is poised to become the world's first land-based commercial SMR, with commercial operation confirmed for H1 2026. In North America, the GE-Hitachi BWRX-300 at OPG's Darlington site in Ontario began construction in May 2025 after receiving a CNSC License to Construct, making it the first SMR construction project on the continent. TerraPower's Natrium plant in Kemmerer, Wyoming received its NRC construction permit in 2025 and targets a 2030 completion. The commercial case for SMRs has been supercharged by data center power demand, with Google, Amazon, Meta, and Microsoft collectively signing agreements for over 10 GW of new nuclear capacity. NuScale remains the only SMR vendor to receive a full NRC design certification, achieved in January 2023 for its original 50 MWe design, with the uprated 77 MWe US460 receiving Standard Design Approval in May 2025.