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Oklo announced that its Groves Isotope Test Reactor has achieved first criticality after achieving a controlled, self-sustaining nuclear chain reaction at low power. The milestone comes less than a year after groundbreaking and follows U.S. Department of Energy (DOE) authorization through the DOE Reactor Pilot Program (RPP).
“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. Taken together, 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 DOE’s RPP created a pathway that allowed engineering, construction, commissioning, and operational preparation to advance alongside DOE’s safety review and authorization. Groves demonstrates that the domestic nuclear industry can once again move from design through construction, authorization, and startup on timelines that are measured in months rather than years when developers, suppliers, and regulators work together on an integrated deployment approach.
"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. We applaud the work of the Oklo, DOE, and Idaho National Laboratory staff who helped achieve this milestone," said Assistant Secretary for Nuclear Energy Ted Garrish.
Groves is part of Oklo Isotopes’ broader effort to build domestic isotope production capabilities for healthcare, industry, research, space, and national security applications. The project has generated practical experience in project engineering, construction, procurement, reactor operations, startup procedures, safety readiness, training, qualification work, and deployment execution that can inform future isotope production facilities.
The Groves project also established engineering practices, operating procedures, training programs, commissioning experience, and organizational capabilities that will reduce uncertainty and execution risk across every Oklo facility, including the company’s future isotope, powerhouse, and fuel cycle deployments.
“Texas is leading America’s nuclear renaissance by advancing the technologies that will power innovation and strengthen our nation's future,” said Governor Abbott. “From expanding our nuclear workforce to rebuilding critical domestic supply chains, Texas is creating the foundation for the next generation of advanced nuclear development. Congratulations to Oklo on reaching this important milestone, which will help expand isotope production for critical medical therapies and reinforce Texas' leadership in nuclear innovation.”
https://oklo.com/newsroom/news-details/2026/Oklos-Groves-Reactor-Achieves-First-Criticality-in-Under-a-Year/default.aspx