5th Small Nuclear Reactor Type Since June Validated and Poised for Mass Production

Another small nuclear reactor has achieved “criticality,” marking the fifth new reactor type to be certified as operationally viable in the United States since June, after none were certified for more than a half-century, as the nation’s “nuclear renaissance” quickly advances to commercial mass-production.Santa Clara, California-based Oklo’s Groves Isotope Test Reactor reached criticality on Aug. 5 at the company’s plant in Lockhart, Texas, and will produce isotopes for medicine, advanced manufacturing, scientific research, space exploration, and national security needs.Unlike massive cement-siloed, utility-scale reactors such as the Westinghouse AP1000, the Groves reactor is a circular 22.5-foot-diameter nuclear generator that can be shipped by truck or rail and planted in a 35-foot-deep reinforced concrete cavity, making it a distinct entry in an expanding range of small, portable reactors on the cusp of being retail ready.Oklo is one of 10 companies selected by the Department of Energy (DOE) in August 2025 to develop 11 “first mover” innovations under a reactor pilot program authorized by President Donald Trump in four May 2025 “Nuclear Renaissance” executive orders that call for licensing 10 new reactors by 2030 and quadrupling the nation’s nuclear energy capacity by 2050.The president’s executive orders included incentives for three prototypes to reach “criticality” by July 4 to commemorate the 250th anniversary of the nation’s founding. That goal was eclipsed when Aalo Atomics’ Aalo-X became the fourth small reactor to attain criticality on July 4 after Antares Nuclear’s Mark-0 on June 4 became the first new reactor type in the United States to achieve the status since 1973.With Oklo’s Groves reactor becoming the fifth to reach criticality in the last two months, Trump’s five-year goal for 10 small reactor types to be validated is already halfway accomplished. Energy Secretary Chris Wright said as many as seven would achieve criticality by year’s end.The Groves reactor is one of two Oklo reactor developments that qualified for the pilot program. The company is also building a 75 megawatt reactor to anchor its Aurora Powerhouse Project at Idaho National Laboratory’s Materials and Fuels Complex, a prototype the company anticipates will be ready for “commercial operations” by 2028.The Groves reactor is also one of two that attained viability in a privately owned plant rather than on the 890-square-mile Idaho National Lab near Idaho Falls.“Thanks to President Trump’s precedent-setting directive to create the Reactor Pilot Program, Oklo’s Groves Isotope Test Reactor is part of the revival of America’s nuclear energy industry,” Assistant Secretary for Nuclear Energy Ted Garrish said in a statement. “We applaud the work of the Oklo, DOE, and Idaho National Laboratory staff who helped achieve this milestone.”United States Energy Secretary Chris Wright speaks with Kiewit Construction Site Manager Marvin Robb (L) and Atlas Engineering Project Manager Hillary Hack during a June 25 tour of Oklo’s Aurora Powerhouse Project at Idaho National Laboratory. John Haughey/The Epoch TimesBuilt in a YearDuring a tour of Idaho National Laboratory in late June, Oklo Co-Founder and CEO Jacob DeWitte said the company’s Groves reactor in Texas would soon reach criticality despite being built from scratch in less than a year.The company began building the open, water-cooled reactor designed to supply domestic radioisotopes for medical imaging, cancer treatments, and national defense in September 2025, he said, and received DOE’s “substantial completion” certification in April, clearing it for criticality.“It’s dang impressive that we hit substantial completion in 227 days, and that we’ll be able to turn that reactor on in critical in less than a year,” he said. “We’re just waiting on the green light to take fuel, load it, and turn it on.”That green light came late on Aug. 5.“Reaching criticality in less than a year is an incredible milestone for our team,” DeWitte said in an Aug. 6 statement. “Oklo developed Groves from a greenfield site on private land, completed full-scale civil excavation and construction, manufactured or commercially procured all components, including fuel, and developed its operating programs in-house.“Taken together,” he added, “we believe these accomplishments establish a new benchmark for the Reactor Pilot Program and set the stage for the future of advanced nuclear deployment at scale.”The nation—the world—is poised to see “advanced nuclear deployment at scale” with the Nuclear Regulatory Commission expected this fall to adopt Part 57, a micro-reactor regulatory framework that trims license reviews from often more than a decade to between six and 12 months.Under Part 57, when the commission issues a license for a prototype reactor, the developer doesn’t need further approvals to mass produce it. Public comment on the rule closed July 15. Commissioners are expected to debate and adopt a final rule no later than early 2027.“Ordering one [reactor] is cool, but ordering 10 is a lot better,” DeWitte said in Idaho. “There’s a future for that, for sure.”Oklo is engaged in multiple nuclear energy projects in addition to its Groves reactor and Aurora Powerhouse, including a fuel fabrication plant prototype to recycle fuels from Idaho National Lab’s Experimental Breeder Reactor-II, idle since 1994; a co-partnership with Nvidia in a fuel project at Los Alamos National Laboratory in New Mexico; and its September 2025 contract with hyperscaler Meta to power a 200-acre data center campus in Pike County, Ohio, with a small reactor by the early 2030s.