Oklo Inc. (NYSE: OKLO) announced that its Groves Isotope Test Reactor in Lockhart, Texas, has achieved first criticality, completing a controlled, self-sustaining nuclear chain reaction at low power. The milestone came less than a year after groundbreaking at the site.

The reactor was built on private land as part of the U.S. Department of Energy's Reactor Pilot Program (RPP), which allowed engineering, construction, commissioning, and operational preparation to proceed alongside the DOE's safety review and authorization process. According to the company, Groves is the first reactor under the program to achieve criticality on a greenfield site on private land.

"Reaching criticality in less than a year is an incredible milestone for our team," said Oklo co-founder and CEO Jacob DeWitte. "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."

Ted Garrish, Assistant Secretary for Nuclear Energy, credited the RPP, established under a directive from President Trump, for enabling the milestone, noting contributions from Oklo, DOE, and Idaho National Laboratory staff.

Oklo said the Groves facility is intended to support domestic isotope production for healthcare, industry, research, space, and national security applications. The company stated that engineering practices, operating procedures, and commissioning experience gained at Groves are expected to inform future Oklo facilities, including planned isotope, powerhouse, and fuel cycle deployments.