Antares Nuclear announced it reached zero-power fueled criticality, the first small‑reactor design to achieve a self‑sustaining fission reaction under the Energy Department’s SMR program. The test produced enough heat to power a single LED, proving the concept but not yet generating usable electricity. Investors see the result as a technical proof point for AI data‑center power needs.

The United States has added only three large reactors this century and has no commercial SMR projects in operation. The DOE launched the program last year to revive nuclear capacity, targeting two additional firms—Oklo and Valar Atomics—to hit criticality by July 4. DOE hopes the effort will jump‑start a market that has stalled despite presidential support.

Next steps for Antares involve scaling the prototype to full power and attaching turbines to generate electricity, with a goal to supply tiny reactors to military bases by 2028. Analysts stress that commercial deployment remains years away, and the company will not supply grid power during the current administration. Antares’ achievement marks progress, but a market‑ready SMR is still distant.