The administration said that Antares’ design, known as Mark-0, successfully completed a zero-power fueled demonstration at the Energy Department’s Idaho National Laboratory. The agency said the test confirmed that the reactor can operate safely, creating a pathway for similar reactors to produce electricity as soon as 2027. 

“It is fitting that on the eve of our nation’s 250th anniversary, we are witnessing a historic moment for American energy,” Energy Secretary Chris Wright said in a statement. “For the first time in more than four decades, a new privately developed non-light-water reactor has reached criticality in the United States.” 

The Mark-0 is the first of several advanced reactors that is expected to reach criticality by July 4. This deadline was set by President Donald Trump last year in a series of executive orders aimed at boosting nuclear energy deployment and quadrupling domestic capacity by 2050. 

Advancing nuclear energy technology is part of the president’s “energy dominance” agenda and efforts to beat China in the race for artificial intelligence. Nuclear energy has become an extremely attractive option for the administration and Big Tech to power AI, as the carbon-free resource is considered one of the most reliable sources of energy.

When the Independence Day deadline was announced, some in the industry doubted that the developers would be able to hit the target, as there has been little progress made on deploying small modular reactors in recent years.

Compared to larger and more traditional nuclear facilities, these small reactors have a smaller physical footprint, allowing them to be built closer to local grids and in less time. Typically, they can generate upward of about 300 megawatts of power. One megawatt can usually produce enough electricity to power 400 to 900 homes. There are no SMRs operational in the U.S. and just a handful are operational worldwide. 

In August of last year, Wright acknowledged during an interview with the Washington Examiner that the goal might be too ambitious, though he remained confident that it was achievable. 

Achieving criticality does not mean that the reactor is fully operational and producing electricity. None of the reactors being developed under the pilot program are expected to produce commercial generation, as they are being built specifically for testing and demonstration purposes. 

Under the Atomic Energy Act, the Department of Energy is not able to license commercial reactors but is instead able to license reactors, often for research purposes, under agency control or under substantial contractual obligations. 

The administration, however, is hopeful that the accelerated pilot program will serve as a fast-tracked bridge for commercial licensing under the Nuclear Regulatory Commission, by providing federal regulators with critical operational data — such as the successful criticality tests. 

Several advanced nuclear developers within the pilot reactor program anticipate they will start submitting license-related applications with the NRC later this year. 

This includes Aalo Atomics, which confirmed to the Washington Examiner last month that it is also on track to hit the July 4th deadline. 

A LOOK BACK ON TRUMP’S EFFORTS TO BOOST NUCLEAR ENERGY ONE YEAR LATER

Now that Antares has achieved criticality, the company expects to produce electricity from its advanced reactors in 2027. It then plans to deploy its reactors at military installations in 2028. 

“What Antares achieved is specifically zero-power criticality — the chain reaction was sustained at essentially no measurable energy output,” INL Laboratory Director John Wagner said. “This is not electricity generation. It is not full-power operation. It is proof that the system works: the scientific and engineering validation that every subsequent step depends on.”