Oklo's Groves Test Reactor Reaches Criticality in Texas in 11 Months

Oklo's Groves test reactor, the firm backed by Sam Altman, reached criticality on August 6, 2026, on private land south of Austin, Texas, approximately 11 months from the start of construction. According to Canary Media, it is the fifth of the ten reactors in the U.S. Department of Energy (DOE) pilot program to achieve a chain reaction in the past two months.

Criticality, the self-sustained chain reaction at low power, is a necessary but not sufficient step toward the commercial deployment of a nuclear reactor. The milestone validates a deployment model measured in months, not years, at precisely the moment when electricity demand from artificial intelligence data centers is straining grids such as ERCOT, the Texas electricity market operator. That tension between load growth and generation capacity also surfaces in discussions about nearshoring in Mexico, where the north is concentrating new industrial plants. Groves is a low-power reactor, a demonstration version of the technology Oklo will use in its medical isotope business, built on a greenfield site in Caldwell County, according to Bloomberg.

The project purchased low-enriched uranium from French company Framatome and completed civil excavation, components, and operating programs in under a year, according to the company. Co-founder and CEO Jacob DeWitte said that achieving criticality in under a year is an important milestone for the team. Texas Governor Greg Abbott stated that the project lays the groundwork for expanding isotope production for medical therapies and reinforces the state's nuclear leadership. Oklo does not yet have a permit to build its commercial 75-megawatt liquid sodium-cooled power reactor: the Nuclear Regulatory Commission (NRC) rejected its application in 2022 and the company has not resubmitted it. The NRC did grant Oklo a license in March 2026 to operate a medical isotope reactor.

The next milestone to watch is the license application to the NRC for Oklo's power reactor and its site adjacent to Idaho National Laboratory, where the company is preparing its first small modular reactor. The company expects its isotope business to generate early revenues before electricity generation comes online.

This article was written with artificial intelligence assistance from verified sources and reviewed by a human editor before publication.