Oklo's Groves Test Reactor Reaches First Criticality
The Department of Energy granted startup authorization on July 23, 2026, and the privately built Groves Isotope Test Reactor achieved first criticality on August 5, 2026.
Oklo (OKLO), the developer of Aurora fast-fission powerhouses, said the Department of Energy granted startup authorization for its Groves Isotope Test Reactor on July 23, 2026, completing the DOE authorization process and allowing fuel loading, startup testing, and reactor operations. On August 5, 2026, the reactor achieved first criticality. The company said the Groves Isotope Test Reactor was the first reactor under the DOE reactor pilot program to reach criticality on private land.
The low-power test reactor, located in Lockhart, Texas, was developed on privately owned land, financed with private capital, and executed with commercially sourced or company-manufactured systems under DOE safety oversight. It is intended to demonstrate reactor design, construction, and operations and to help establish experience for future isotope production facilities.
During the three months ended June 30, 2026, the project advanced through a series of DOE safety and authorization milestones. The Nuclear Safety Design Agreement had been approved on March 17, 2026. The Preliminary Documented Safety Analysis was approved on May 27, 2026, and the Documented Safety Analysis on June 30, 2026. The company said the Groves Isotope Test Reactor provides an organizational and operational foundation from which future isotope facilities can advance, each of which will still require project-specific engineering, safety analysis, licensing, and execution.
In parallel, the isotope business received a materials license from the NRC authorizing the Idaho Radiochemistry Laboratory to handle, process, and distribute licensed radioactive materials, supporting initial commercial isotope processing and supply activities.
On the flagship Aurora powerhouse at Idaho National Laboratory, the DOE approved the Preliminary Documented Safety Analysis on June 11, 2026, under the reactor pilot program. The PDSA establishes the preliminary safety basis, including hazard analysis, accident analysis, safety controls, and design commitments that support continued advancement of final design and construction. In the prior quarter, the company had described the PDSA as submitted but not yet approved. Early in 2026, the DOE had already approved the Nuclear Safety Design Agreement. The DOE and INL had completed the environmental compliance process for site characterization, resulting in an Environmental Compliance Permit.
A Notice of Intent to Award was issued by the Defense Logistics Agency-Energy on behalf of the Department of the Air Force, tentatively selecting Oklo to provide electricity and heat, including at least 5 MWe, to Eielson Air Force Base outside Fairbanks, Alaska. The company said an Aurora-derived powerhouse is planned for the base.
Fuel and customer work continued. In June 2026, Oklo entered a letter of intent with Centrus Energy Corp. under which Centrus would supply sufficient domestically produced HALEU to support multiple years of fuel requirements for up to five Aurora powerhouses, with deliveries expected to begin in 2029. The LOI contemplates a definitive supply agreement and could include prepayments to support the planned 1.2-GW power campus in Pike County, Ohio, under a January 5, 2026, prepayment agreement with Meta Platforms, Inc. Timing, volume, pricing, and prepayment terms remain subject to negotiation.
In May 2026, the company said it had been selected by the DOE for advanced negotiations under the DOE’s Surplus Plutonium Utilization Program, which aims to make designated surplus plutonium available for conversion into fuel for advanced nuclear reactors. Any use would be subject to DOE authorization, regulatory approvals, and material-availability determinations. In June 2026, Oklo entered a nonbinding memorandum of understanding with Standard Nuclear, Inc. to explore purchases of recycled nuclear fuel materials.
During the quarter, the company also announced two collaborations supporting the federal Genesis Mission. In April 2026, it agreed with NVIDIA Corporation and Los Alamos National Laboratory to advance AI-enabled modeling, simulation, digital twins, materials science, and fuel validation for plutonium-bearing fuels, as well as power generation and grid studies supporting potential nuclear-powered AI infrastructure at Los Alamos. In May 2026, it announced a partnership with Battelle Energy Alliance to integrate INL’s Prometheus AI platform with Oklo’s multiphysics design infrastructure and to support development of Pluto, its plutonium-fueled reactor system under the DOE RPP.
The company has an ambitious target of deploying its first powerhouse in 2028. It continues to engage with the NRC and is evaluating the timing and form of future NRC applications in light of evolving federal policy, including the recently finalized Part 53 framework and proposed Part 57 framework, while Aurora-INL progresses under DOE authorization.