Three Advanced Reactors Achieved Criticality Before July 4th, Fulfilling Trump's Executive Order Goal

What Happened

Three advanced microreactors achieved criticality in the United States in June and July 2026, meeting a deadline President Trump set in Executive Order 14301, signed in May 2025. The order directed the Department of Energy to authorize a reactor testing program and reach the criticality milestone in at least three reactors by July 4, 2026.

Antares Nuclear was first. Its Mark-0 sodium heat pipe reactor achieved zero-power criticality on June 4 at Idaho National Laboratory, according to the DOE. Secretary of Energy Chris Wright called it "the first of multiple advanced reactors anticipated to go critical by the July 4th deadline" and noted it was the first privately developed non-light-water reactor to reach criticality in the U.S. in more than four decades.

Valar Atomics reached the milestone second. Its Ward 250 gas reactor achieved criticality on June 22, also at DOE facilities in Utah. According to ZeroHedge, Valar went a step further and live-streamed critical safety testing while the reactor was producing nuclear heat.

Deployable Energy's Unity microreactor completed the trifecta. The Houston-based company's 1-megawatt electric, high-temperature, gas-cooled reactor achieved criticality late on June 30, just before midnight Mountain Time, at Idaho National Laboratory, according to the DOE announcement on July 1.

A Key Distinction

The American Nuclear Society flagged something the DOE's press release glossed over: Deployable Energy is NOT technically a member of the Reactor Pilot Program created specifically under EO 14301.

The RPP selected 11 reactor projects: Aalo Atomics, Antares Nuclear, Atomic Alchemy, Deep Fission, Last Energy, Oklo (two projects), Natura Resources, Radiant Industries, Terrestrial Energy, and Valar Atomics. Deployable Energy was not on that list.

Instead, Deployable was selected in late April 2026 for the Nuclear Energy Launch Pad, a separate DOE initiative designed to extend RPP-like opportunities to companies outside the original program. The American Nuclear Society noted that "the letter of EO 14301 may not yet have been met" but concluded that "its spirit nonetheless has: three DOE-authorized advanced reactors have reached criticality."

The DOE's own press release on Deployable's milestone did not draw this distinction. The omission matters because the distinction exists.

What the Reactors Actually Are

All three are microreactors, not the giant light-water plants that dominate the existing U.S. grid. These are designed for factory manufacturing and rapid deployment in remote locations, military installations, data centers, and behind-the-meter industrial applications.

Deployable Energy's Unity uses standard low-enriched uranium dioxide fuel with an actively cooled helium primary loop, according to the Nuclear Regulatory Commission. The company told the NRC it has secured over $10 billion in letters of intent from customers ranging from data centers to remote island communities.

Antares Nuclear's Mark-0 was the 53rd reactor built at the Idaho National Laboratory site since 1951, according to the DOE. When commercialized, microreactors like it are anticipated for terrestrial, space, and military applications.

The Case for Skepticism

Critics of the program make a fair point: zero-power criticality is not the same as a commercial power plant. These reactors sustained a fission chain reaction under controlled conditions. They did NOT generate electricity for a grid. Full commercial deployment still requires NRC licensing, which Deployable Energy has only begun through a letter of intent and preapplication engagement. The path from criticality to electrons reaching homes or data centers is measured in years, not months.

That skepticism is legitimate. The DOE's own language acknowledges Antares's commercialization timeline as "2027 and beyond." Whether the aggressive EO-driven schedule produced durable, fully validated designs, or rushed prototypes that still face years of regulatory scrutiny, is a question the data doesn't yet answer.

Assistant Secretary of Nuclear Energy Scott Melbye directly addressed the doubt: "The skeptics didn't believe President Trump's Reactor Pilot Program could achieve criticality in less than a year." On that specific metric, the program delivered.

Where This Sits in the Bigger Picture

The U.S. now has three advanced non-light-water reactor designs that have sustained a fission reaction under DOE authorization in 2026. That is a measurable, documented fact regardless of where one sits politically.

The open question is whether this pace continues. Eight of the original 11 RPP selectees have not yet achieved criticality. The DOE has not announced updated timelines for those remaining projects. Whether the Reactor Pilot Program and Nuclear Energy Launch Pad can move these designs through NRC licensing on any comparable schedule will determine whether this month's milestones become the foundation of a genuine commercial nuclear expansion or remain celebrated proofs of concept.