TerraPower's edge for data centres is a vat of hot metal, not the reactor

TerraPower plans to announce its first data centre project this year, according to Bloomberg reporting cited by TechCrunch, with the plant expected to break ground in 2027 ^{[1] [4]}. What matters is not the announcement but the heat plumbing: the design lets the reactor keep running at full power while the plant's electrical output moves, which is the specific behaviour a GPU cluster demands and most reactors cannot supply ^{[18] [19] [13]}.

Start with the constraint every nuclear operator lives under. In the US, reactors generate at maximum power 92.5% of the time, the highest capacity factor of any generating type ^[7]. That is partly a virtue and partly a limitation: existing reactors can increase or decrease output by only about 5% of rated capacity per minute, according to the National Laboratory of the Rockies as cited by TechCrunch ^[8]. Newer small modular designs roughly double that, to about 10% per minute ^[9]. Even at the faster figure, walking a plant from rated output down to zero takes ten minutes, against twenty for the incumbent fleet ^[10]. Neither number is in the same time domain as an inference workload.

The economics bite harder than the physics. Nuclear carries the highest capital expenditure of any generating technology ^[11], so every hour spent below rated output is an hour of unrecovered fixed cost ^[22]. Startups are betting that mass manufacturing pulls capex down, but that has not been demonstrated, and TechCrunch notes any benefit could take a decade or more to arrive ^[12]. Meanwhile, data centre loads sink and soar quickly as GPUs pick up and drop tasks ^[13]. Those swings have been severe enough to break natural gas turbines ^[14], and the usual fix, large banks of batteries, adds cost on top of the generator ^[15].

TerraPower's answer is to stop treating the reactor as the throttle. Its 345-megawatt unit keeps splitting atoms at a constant rate, and surplus heat goes into a large reservoir of molten sodium; when demand spikes, the plant draws on that store to raise more steam and spin the turbines harder ^{[16] [18] [19]}. The reactor, the most expensive equipment on site, therefore runs during low-demand hours instead of idling, and the capital is amortised over more operating hours ^[20]. Worth noting that TechCrunch describes the same unit as "molten salt-cooled" while placing the storage inventory in molten sodium, so the published description of the coolant and storage media is not internally consistent ^{[16] [18]}.

The load-following requirement did not come from AI. TerraPower designed for a wind-and-solar-heavy grid, where the plant has to move around intermittent generation ^[17]; the company had renewables, not data centres, in mind when it drew the plans ^[21]. Intermittency on the demand side turns out to want the same machine.

Three things to watch. The customer is unnamed ^[2], and the obvious candidate is Meta, which agreed in January to buy eight Natrium plants ^[3], so confirmation either validates that pipeline or reveals a second buyer. Whether the 2027 groundbreaking holds is the real test, given this would be only the company's second plant, with the first still under construction in Wyoming ^{[4] [5]}. And watch whether a data centre customer accepts thermal storage in place of the battery bank it would otherwise buy ^[15].