TerraPower's $4 billion Natrium sodium-cooled fast reactor project in Kemmerer, Wyoming, depends on high-assay low-enriched uranium enriched to around 19 percent uranium-235. For years, the only commercial supplier of that material was Russia — and when trade fractured in 2022, TerraPower lost access to its fuel supply, pushing the Natrium timeline back at least two years.

Fuel as the critical path

Natrium is a case study in how HALEU availability, not reactor engineering, can set a project's schedule. The reactor design was ready to advance; the fuel was not. That dependency is now being addressed: Centrus Energy has restarted HALEU production at Piketon, Ohio, as part of a U.S. effort to rebuild a domestic HALEU fuel supply chain capable of serving advanced reactor designs.

TerraPower lost access to its Russian HALEU supply after trade fractured in 2022, delaying the Natrium project timeline by at least two years.

The reactor design

Natrium circulates liquid sodium, which melts at 208°F and boils at roughly 1,600°F. The core runs at about 900°F with no pressure, eliminating steam-burst risk and allowing a factory-style building rather than a large containment dome. The plant integrates molten salt heat storage, holding back 345 MW of thermal output and surging to 500 MW of electrical power for more than five hours — a configuration aimed at following load rather than running flat out.

Why Kemmerer

TerraPower chose Kemmerer, Wyoming, population 2,600, because the retiring Naughton coal plant left behind high-capacity transmission lines and a skilled steam-turbine workforce. The company broke ground on the non-nuclear portions of the site in June 2024, with power expected around the end of the decade.

What the Natrium timeline shows

Two lessons stand out for the wider advanced reactor sector. First, enrichment capacity is a gating item: a reactor project can be fully designed, sited and permitted and still wait on fuel. Second, supply concentration carries schedule risk — a single-source dependency converted a geopolitical rupture into a multi-year construction delay.

The restart of production at Piketon is a necessary first step, but scale remains the open question. Natrium's fuel needs must be met alongside those of other first-of-a-kind reactors and demonstration programs, all competing for early output from a supply chain that is only beginning to restart.

This article was assisted by AI analysis. Please refer to the original source for official information.