The AI power problem has become one of those things everyone in tech mentions in the same breath as "grid queue," "seven-year interconnect wait," and "we'll figure it out."

Hyperscalers keep signing gigawatt deals with existing nuclear plants. Microsoft locked up Three Mile Island's 835 MW under a 20-year power purchase agreement, and Amazon secured 1.92 GW from Talen's Susquehanna plant. But those are old reactors being kept alive or switched back on, not new ones being built. New nuclear was always going to take a decade.

Until last month, when the US quietly took three brand-new reactors critical in thirty days. Not gigawatt behemoths, but microreactors the size of a shipping container, small enough that one founder drove the core of his machine to Idaho Falls in the back of a Ford F-150.

And the data center industry is already trying to figure out how to buy them.

Three reactors, one month, one presidential deadline

The setup goes back to May 23, 2025, when Executive Order 14301 told the Department of Energy to stand up a Reactor Pilot Program and get at least three advanced reactors to criticality by July 4, 2026, the country's 250th birthday.

Criticality is the milestone: the moment the core sustains its own controlled chain reaction. It's the difference between a nuclear machine and a very expensive metal sculpture.

The DOE beat the deadline with days to spare. Antares Nuclear's Mark-0 got there first on June 4 at Idaho National Laboratory, becoming the 53rd reactor ever built at the site since 1951 and, per the DOE, the first privately funded non-light-water design to go critical there in four decades.

Valar Atomics' Ward 250 followed on June 22, per the American Nuclear Society, and not in Idaho: Valar runs its own test site at the San Rafael Energy Lab in Emery County, Utah. It was actually the startup's second criticality, after an earlier core-only test at Los Alamos.

Deployable Energy's Unity completed the sweep at 11:55 PM on June 30, per the company's announcement, back at Idaho National Laboratory. The DOE says no country had ever taken three distinct advanced microreactor designs critical in a single month. Energy Secretary Chris Wright called it "a significant milestone on a timeline many thought was unachievable."

Each machine is a different bet on the physics. Antares' Mark-0 is a sodium heat-pipe-cooled design running HALEU TRISO fuel, modeled on the fuel compacts BWXT built for the Army's Project Pele. Valar's Ward 250, roughly the size of a minivan, is a TRISO-fueled high-temperature gas reactor cooled with helium.

Deployable took a different route entirely. Unity is water-moderated and helium-cooled, and runs on standard 4.95% enriched uranium dioxide, per POWER magazine, with commercially available materials instead of HALEU or exotic components. Which is another way of saying: they built one out of parts you can actually source.