Oklo today 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).

Oklo shares jumped 5.3% in premarket trading.

“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.