Four nuclear reactors achieved criticality by the Trump administration’s July 4, 2026 deadline, exceeding the goal of three advanced test reactors and marking a milestone in the push for rapid deployment of next-generation nuclear energy technology.
Antares Nuclear’s Mark-0 reactor reached criticality first on June 4 at Idaho National Laboratory, the first time in over 40 years that a new privately developed non-light-water nuclear reactor achieved this milestone in America. Valar Atomics’ Ward 250 followed on June 18 at Utah’s San Rafael Energy Lab, and Deployable Energy’s Unity completed a criticality demonstration on June 30, also at Idaho National Lab. Aalo Atomics narrowly met the deadline when its Aalo-X microreactor achieved initial criticality at 12:20 a.m. on July 4 at Idaho National Lab.
The achievement stems from executive orders President Trump signed in May 2025 that reformed nuclear reactor testing and directed the Department of Energy to launch a pilot program. The orders streamlined permitting and construction timelines to enable the rapid development of advanced reactors by private companies.
Energy Secretary Chris Wright described the moment as a turning point for American energy. “We will look back in history and remember this pivot, not just in America’s nuclear energy, but in America’s energy,” Wright said in a June 25 speech at Idaho National Lab, referring to the event as “nuclear Woodstock.”
The four companies represent a new wave of nuclear startups developing smaller, modular designs intended to reduce costs and accelerate deployment compared to conventional large reactors. The pilot program selected 10 companies in August 2025, with the four successful reactors now demonstrating that the compressed timeline was achievable.
A Broader Vision for Nuclear Energy
The July 4 milestone is a first step toward a much larger ambition. The Trump administration has set a goal of 400 gigawatts of nuclear capacity by 2050, roughly quadrupling current U.S. nuclear output. Idaho National Laboratory Director John Wagner stated the objective plainly: “The goal is energy dominance.”
Beyond the pilot program, the administration is supporting the restart of previously shuttered nuclear plants and financing new large-scale commercial reactors. In June 2026, the Energy Department announced financing for long-lead time supply chain items to accelerate deployment of 10 new commercial nuclear reactors. The department is also supporting the restart of Palisades, an 800-megawatt nuclear station in Michigan, and the Crane Restart project, an 835-megawatt plant in Pennsylvania.
The rapid development has raised concerns among some nuclear safety experts, who worry that compressed timelines could lead to mistakes. Environmental advocates remain divided, with some arguing that nuclear energy is cleaner and safer than fossil fuels, while others contend the U.S. should focus on proven renewable technologies like solar and wind. The four successful reactors demonstrated that initial tests were successful, but the long-term safety and commercial viability of these designs remain to be proven as they move toward electricity production in 2027 and beyond.
The Trump administration has also expanded its data center power pledge to cover 80 percent of U.S. electricity, reflecting the broader strategy of using advanced nuclear reactors to meet surging energy demand.
Sources
- U.S. Department of Energy — confirmed four reactors achieved criticality by July 4, 2026; details on the four companies, dates, and locations; Energy Secretary Chris Wright’s “nuclear Woodstock” quote
- Wyoming Public Media — reported on the July 4 deadline achievement, company names, and Idaho National Lab Director John Wagner’s “400 gigawatts by 2050” and “energy dominance” quotes
- Energy.gov — provided details on the May 2025 executive orders, the pilot program structure, and the administration’s broader nuclear strategy including plant restarts and commercial reactor financing
