Three reactors are leading the US small modular reactor race in 2026, each representing a fundamentally different technology pathway. TerraPower's Natrium is a 345 MWe sodium-cooled fast reactor with integrated molten salt energy storage, backed by Bill Gates and a $4B DOE cost-share. GE Hitachi's BWRX-300 is a 300 MWe simplified boiling water reactor already under construction at OPG Darlington in Ontario. X-energy's Xe-100 is an 80 MWe helium-cooled high-temperature gas reactor using TRISO pebble fuel, with Amazon backing up to 12 units. This page compares their specifications, NRC status, cost estimates, timelines, and commercial partnerships to answer the question: which SMR will define the next era of nuclear power?
| SPECIFICATION | NATRIUM | BWRX-300 | XE-100 |
|---|---|---|---|
| Developer | TerraPower | GE Hitachi / GE Vernova | X-energy |
| Electrical Output | 345 MWe | 300 MWe | 80 MWe |
| Thermal Output | 840 MWth | 870 MWth | 200 MWth |
| Reactor Type | SFR | BWR | HTGR |
| Coolant | Liquid sodium | Light water | Helium |
| Fuel Type | HALEU metallic | LEU UO2 | TRISO pebble |
| Enrichment | HALEU (5-20%) | <5% LEU | HALEU (5-20%) |
| Modules Per Plant | 1 | 1 | 4 |
| Construction Timeline | 60 months | 48 months | 48 months |
| NRC / Regulatory Status | NRC Construction Permit Received (March 2026) | CNSC Licence to Construct (April 2025) | NRC CP Application Under Review |
| Target First Operation | 2030 | 2029 | 2030 |
| Passive Safety | Yes | Yes | Yes |
| Load Following | Yes | Yes | Yes |
| Country | USA | USA | USA |
| Status | Under Construction | Under Construction | In Licensing |
Founded by Bill Gates. 345 MWe baseload with 500 MWe peak via molten salt energy storage. Lead project in Kemmerer, Wyoming — first utility-scale advanced nuclear plant in US. DOE cost-share up to $2B of $4B total. Meta deal for up to 8 plants (2.8 GW).
Simplified boiling water reactor with natural circulation. Lead project at OPG Darlington, Ontario — first SMR construction in North America. Construction began May 2025.
80 MWe per module, 4-pack configuration yields 320 MWe. TRISO-X fuel facility (TX-1) NRC licensed Feb 2026. Dow Seadrift project: 4 units. Amazon/Energy Northwest: up to 12 units at Cascade facility. DOE ARDP award up to $1.2B.
Each reactor serves a different market. The BWRX-300 is the lowest-risk path to deployment — it uses proven light water technology, conventional LEU fuel with no HALEU dependency, and is already under construction at Darlington. It will likely be the first operating SMR in North America. Natrium is the highest-ambition design — a Generation IV sodium-cooled fast reactor with integrated energy storage, backed by Meta's 2.8 GW commitment and a $4B first-of-a-kind plant in Wyoming. If it works, it redefines nuclear economics; but it faces HALEU fuel supply risk and first-of-a-kind construction risk. The Xe-100 occupies the middle ground — a modular, factory-fabricated HTGR using TRISO fuel that cannot melt, with Amazon and Dow as anchor customers. Its 80 MWe module size enables incremental deployment. For investors, BWRX-300 exposure comes via GE Vernova (GEV). TerraPower and X-energy are not publicly traded. The technology that wins will be the one that delivers on schedule and on budget — and right now, BWRX-300 leads that race.