Oklo Reactor Reaches Criticality in Texas Under Federal Program

The Groves Isotope Test Reactor, developed by Oklo Inc., reached criticality on August 5, 2026, at the company's plant in Lockhart, Texas. The portable, water-cooled generator is designed to produce isotopes for national security, scientific research, and medicine. Oklo completed the project from a greenfield site in less than a year, reaching substantial completion in 227 days.

This achievement marks the fifth new small modular reactor type certified as operationally viable in the United States since June, following the Mark-0 from Antares Nuclear and the Aalo-X from Aalo Atomics. The project was developed under a Department of Energy reactor pilot program authorized by President Donald Trump's May 2025 executive orders, which aim to license 10 new reactors by 2030.

Beyond the Texas site, Oklo is developing a 75 megawatt reactor at the Idaho National Laboratory and has secured a contract with Meta to power an Ohio data center by the early 2030s. U.S. Energy Secretary Alfie Moon projected that up to seven reactors could achieve criticality by the end of the year.