Four small nuclear energy startups have quietly hit a milestone that the industry hasn’t managed in decades: getting a privately funded advanced reactor to “criticality,” the point where a chain reaction becomes self-sustaining. The four privately funded micro-reactor developers reached that stage, and the White House marked the moment with an Oval Office event featuring the companies’ CEOs alongside the president.
The achievement traces back to a pilot program launched via executive order in May 2025, which challenged private firms to get at least three advanced reactors operational by July 4, 2026 — the country’s 250th anniversary. Four companies beat that deadline, delivering what officials called the first privately funded advanced reactors in the U.S. in more than 40 years, with Antares Nuclear, Valar Atomics, Aalo Atomics and Deployable Energy among the firms involved.
The push reflects a broader bet that nuclear power will be essential to meeting the country’s surging electricity demand, driven largely by AI data centers. The administration has said it wants to roughly quadruple U.S. nuclear capacity by 2050, even as nuclear’s overall share of U.S. electricity generation has actually slipped slightly in the past decade. Separately, the Interior Department said this week it had reached an agreement with the Nuclear Regulatory Commission to jointly oversee any future nuclear projects built in federal waters off the coast — a sign officials are looking at offshore siting as one option for the next wave of reactors.
Officials framed the milestone as proof that the regulatory bottlenecks long blamed for nuclear power’s stagnation can be cleared quickly when there’s political will behind it. Whether that pace holds as these reactors move from “criticality” to actually supplying power to the grid — and whether the public and utilities embrace them at scale — remains the bigger open question.