Nuclear Reactor First to Reach Critical Milestone, Wright Says

The Energy Department said Friday that a small nuclear reactor under development at a national lab has reached a crucial milestone that could allow it to produce electricity within a few years. The microreactor being developed by Antares Nuclear Inc. at the Idaho National Lab reached "criticality" on Thursday, Energy Secretary Chris Wright said. The milestone occurs when a nuclear reactor achieves a self-sustaining chain reaction capable of producing a steady release of energy, the AP reports. Antares is the first private company to bring an advanced reactor to criticality under a pilot program begun last year by the Trump administration meant to supercharge nuclear energy production in the US.

"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." The demonstration was conducted in partnership with the Energy Department and other contractors with support from the Army. The achievement shows that the Trump administration's push to remove regulatory barriers is helping to advance new nuclear technologies, Wright said. President Trump signed executive orders in May 2025 intended to speed up the development of nuclear power, including steps that grant Wright the 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 US 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. While the Antares system is years away from commercial use, achieving criticality is a notable step. The company, which is initially targeting military applications, said it expects to begin producing electricity by late 2027, CEO Jordan Bramble said Friday. He said achieving criticality "is the first step on a roadmap toward producing electricity ahead of deploying this technology for customer sites." Edwin Lyman, director of nuclear power safety at the Union of Concerned Scientists, wrote in an email that "this stunt is a rudimentary first step that has absolutely no bearing on whether the Antares reactor will be safe or commercially viable."