Federal officials announced that a compact nuclear reactor being tested at a national laboratory has accomplished a significant breakthrough that could bring it closer to generating power in the coming years.
The small reactor created by Antares Nuclear Inc. at the Idaho National Lab achieved “criticality” on Thursday, according to Energy Secretary Chris Wright. This important phase happens when a nuclear reactor establishes a self-sustaining chain reaction that can produce consistent energy output.
Antares became the first private enterprise to reach this critical stage with an advanced reactor through a pilot initiative launched last year by the Trump administration designed to accelerate nuclear energy development across the United States. The project was carried out in collaboration with the Energy Department and additional contractors, with backing from the U.S. Army.
“We are very excited by this news today,” Wright said Friday on a call with reporters. “I think June 4th will be a historic day in the American nuclear renaissance.”
Antares and its partners “have shown America can do bold things,” Wright added. “America has great technology, great entrepreneurs that are ready to drive energy innovation to power our future, lower energy costs and make our country more powerful.”
Wright stated that this accomplishment demonstrates how the Trump administration’s efforts to eliminate regulatory obstacles are helping advance innovative nuclear technologies.
President Donald Trump signed executive orders in May 2025 intended to speed up the development of nuclear power, including steps that grant Wright authority to approve some advanced reactor designs and projects. Trump’s orders limit some authority of the Nuclear Regulatory Commission, the independent safety agency that has regulated the U.S. nuclear industry for five decades.
Skeptics warn that nuclear energy poses risks and say microreactors may not be safe or feasible and have not proved they can meet demand for a reasonable price.
Though the Antares technology remains years from commercial deployment, reaching criticality represents a significant advancement. The California-based company, which initially focuses on military uses, anticipates beginning electricity generation by late 2027 and deploying systems in operational settings by the end of 2028, according to CEO Jordan Bramble on Friday.
“Nuclear in America has been defined for too long by delays, by companies that said they would and then didn’t,” Bramble said in a written statement.
During Friday’s briefing, Bramble explained that reaching criticality “is the first step on a roadmap toward producing electricity ahead of deploying this technology for customer sites.”
“Microreactors are a technology that’s here today,” he added. “2026 is the year where microreactors are becoming real. We’re months to years out from being able to start deploying this technology to military installations.”
The Trump administration has established an objective of reaching the criticality phase in no fewer than three test reactors by July 4 — the nation’s 250th anniversary.
Officials have chosen 11 advanced reactor projects, including Antares, to advance their technologies toward deployment.
In February, the Pentagon and the Energy Department for the first time airlifted a small nuclear reactor from California to Utah, demonstrating what they say is the country’s potential to quickly deploy nuclear power for military and civilian use. The nearly 700-mile flight transported a 5-megawatt microreactor manufactured by Valar Atomics in southern California to Hill Air Force Base in Utah.
The reactor — which did not have nuclear fuel — eventually will be able to generate up to 5 megawatts of electricity, enough to power 5,000 homes, said Isaiah Taylor, CEO of Valar Atomics. The company hopes to start selling power on a test basis next year and become fully commercial in 2028, he said.
Edwin Lyman, director of nuclear power safety at the Union of Concerned Scientists, said the transport flight, which attracted significant news coverage, was little more than a publicity stunt.
He offered a similar response to the claims by Antares and Wright.
“This stunt is a rudimentary first step that has absolutely no bearing on whether the Antares reactor will be safe or commercially viable,” Lyman said in an email Friday.
The Energy Department’s statement that the test “confirms that the reactor can operate safely” is false, Lyman said, adding that more testing of the reactor is needed.
