TerraPower's Kemmerer 1 Enters Construction: Timeline of the Natrium Project's Road to First Power
POWER Magazine (Access Intelligence, LLC)Sonal C. Patel23 Apr 2026all-rights-reservedRead the original
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TerraPower began nuclear construction on Kemmerer Unit 1 in Wyoming on 23 April 2026, the flagship deployment of its Natrium design — a sodium-cooled fast reactor paired with a molten-salt thermal storage system that lets the plant vary its electrical output independently of reactor power. The start followed the Nuclear Regulatory Commission's authorisation on 4 March 2026 of a Part 50 construction permit, the first the NRC had issued for a commercial power reactor in almost a decade and the first for a non-light-water commercial design in more than forty years. TerraPower had already been building the plant's non-nuclear portions, including the sodium and energy-storage systems, under a separate track before the permit was granted, a sequencing choice intended to compress the schedule.
Quotation
“"TerraPower on April 23, 2026, officially started construction on Kemmerer Unit 1, its flagship Natrium sodium-cooled fast reactor plant in Kemmerer, Wyoming."”
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The MyGreenSuit briefing
Commentary by MyGreenSuit, not the words of POWER Magazine (Access Intelligence, LLC).
The engineering headline is a sodium-cooled fast reactor. The commercial headline is the salt tank bolted to it.
Natrium's thermal storage lets the plant's electrical output swing independently of the reactor's thermal output, which means TerraPower are not really selling baseload. They are selling a nuclear plant that behaves like a peaker, into a grid where the scarcest thing is dispatchable capacity that turns up on a still January evening. That is a considerably better product than "carbon-free baseload," and it is the part most coverage skips.
The regulatory fact underneath deserves its own note. This is the first NRC construction permit for a commercial power reactor in nearly a decade, and the first ever for a non-light-water design. Whatever happens at Kemmerer, that pathway is now open.
Hold the schedule lightly. Vogtle ran years late and far over budget. TerraPower have hedged by building the non-nuclear side first, which is smart, but nobody has built one of these on time because nobody has built one.