Oklo's Groves Isotope Test Reactor achieved criticality at 9:19 p.m. EDT on Wednesday at the company's greenfield facility in Lockhart, Texas, making it the fifth Department of Energy-authorized reactor to reach the milestone under the agency's Reactor Pilot Program.
A First On Private Land
The 15-MWt pool-type, water-cooled, nonpressurized Groves reactor is the first reactor authorized under the DOE's accelerated pathway to go critical on private land. Prior RPP entrants Antares, Valar Atomics, Aalo Atomics and DOE Launch Pad participant Deployable Energy all reached criticality at Idaho National Laboratory or Utah's San Rafael Energy Lab. Oklo says it developed Groves from a greenfield in under a year, handling civil excavation, procurement, fuel and operating programs in-house.
From Test Bed To Isotope Factory
Groves is the flagship project of Oklo Isotopes, the subsidiary formed after Oklo acquired Atomic Alchemy in 2025. The company positions the reactor as a template for future production-scale isotope facilities that will supply medical, industrial and space applications, with lessons learned from Groves feeding into Oklo's commercial SMR and fuel-cycle roadmap.
Aurora And Pluto Still In Queue
Alongside Groves, Oklo is progressing the 75-MWe liquid-metal-cooled Aurora Powerhouse at Idaho National Laboratory and a plutonium-fueled Pluto reactor. Executive Order 14301 had set July 4 as the target for at least three DOE test reactors to achieve criticality, a bar the RPP has now cleared five times over. Texas Governor Greg Abbott called the milestone a boost to state efforts to "rebuild critical domestic supply chains" for medical isotopes and advanced nuclear.
Reporting based on coverage from ANS Nuclear Newswire and Oklo.