Oklo’s Groves Isotope Test Reactor achieved criticality on August 6, 2026, at its facility in Lockhart, Texas. The event occurred at 9:19 p.m. EDT, marking the fifth Department of Energy-authorized reactor to reach this milestone under the agency’s current authorization process. Notably, Groves is the first DOE-authorized reactor to achieve criticality on private land.
What it means
The 15-MWt thermal power reactor serves as a test platform for future production-scale isotope production reactors. Oklo, based in Santa Clara, California, acquired radioisotope production company Atomic Alchemy in 2025 to form Oklo Isotopes. The company stated that domestic production facilities will support sectors including health care, industry, research, space, and national security.
Achieving criticality by August 6 places Oklo among the companies meeting the goals set by Executive Order 14301, which established a target for at least three test reactors to reach criticality by July 4. Other participants in the DOE’s Reactor Pilot Program or Nuclear Energy Launch Pad that reached criticality by that deadline included Antares, Valar Atomics, Deployable Energy, and Aalo Atomics. Work at Groves provides experience in project engineering, construction, procurement, reactor operations, startup procedures, safety readiness, training, qualification work, and deployment execution.
Texas Gov. Greg Abbott welcomed the news from Lockhart, stating, “From expanding our nuclear workforce to rebuilding critical domestic supply chains, Texas is creating the foundation for the next generation of advanced nuclear development.” Oklo cofounder and CEO Jacob DeWitte said, “Reaching criticality in less than a year is an incredible milestone for our team.”
Key facts
- Groves Isotope Test Reactor achieved criticality on August 6, 2026.
- Location: Lockhart, Texas facility.
- Thermal power rating: 15-MWt.
- Fifth DOE-authorized reactor to reach criticality under the current process.
- First DOE-authorized reactor to achieve criticality on private land.
- Executive Order 14301 set a goal for three test reactors by July 4.
- Oklo acquired Atomic Alchemy in 2025, forming Oklo Isotopes.
- Supports health care, industry, research, space, and national security sectors.
Source: American Nuclear Society