The US Department of Energy (DOE) has approved the Documented Safety Analysis (DSA) for Oklo’s Groves Isotope Test Reactor in Lockhart, Texas. This key approval under the Reactor Pilot Program (RPP) marks the completion of the project’s final safety documentation process and advances the reactor into its final pre-startup phase.
The DSA is the facility’s final safety basis grounded on a detailed technical analysis of potential hazards, safety controls, and operating requirements needed to support safe startup. The DSA approval follows DOE’s approval of the Preliminary Documented Safety Analysis (PDSA), which established the facility’s preliminary safety basis during design and construction.
The Groves facility features a 15 MWt pool-type, water-cooled, non-pressurised advanced reactor that relies on low-enriched uranium fuel. It is the first advanced reactor project on privately owned land to secure DSA approval while using entirely commercially sourced fuel, equipment, and systems. The plant will not generate electricity. Instead, it is dedicated to creating a domestic supply chain for critical medical and industrial radioisotopes used in cancer treatment, space exploration, and national security.
With the comprehensive hazard evaluations and operating controls of the DSA formally locked in, the Groves reactor must now navigate a short checklist before beginning full operations. These include a DOE Readiness Review – an administrative and physical check to confirm all personnel, safety systems, and infrastructure are aligned with the approved DSA. Formal approval from the federal government is also required. This will enable fuel loading and initialisation testing. Oklo is targeting first criticality for Groves in July.
The Groves Isotope Test Reactor was built to secure a domestic supply of medical and industrial isotopes, acting as the immediate pipeline to near-term revenue, paving the way for Oklo’s fast-neutron, liquid-metal-cooled Aurora Powerhouse reactors being developed at the Idaho National Laboratory (INL) site.
Groves is based on a Versatile Isotope Production Reactor (VIPR) system built specifically for harvesting nuclear medicine feedstocks. Groves features a 15 MWt light-water-cooled, open-pool type design. The reactor core sits submerged at the bottom of a deep, unpressurised pool of water. Because the pool is non-pressurised, it eliminates the thick steel pressure vessels and complex piping used in commercial nuclear plants.
The pool water serves strictly as a static radiation shield and a thermal heat sink. Unlike power-generating cores optimised to extract heat, the Groves VIPR core is geometrically optimised to produce high neutron fluxes. Specialised irradiation tubes line the perimeter of the core. Technicians insert stable target materials (such as disused radium sources or base metals) into these channels. The intense neutron bombardment transmutes these materials into high-purity radioisotopes.
Once irradiated, the material is shipped to the Idaho Radiochemistry Laboratory (operated by Oklo’s partner, Atomic Alchemy) to be refined into clinical-grade medicine. To fulfil its mission as a fast-tracked commercial pilot, Groves avoids exotic fuel requirements by using standard low-enriched uranium fuel. This allowed Oklo to bypass state-funded enrichment laboratories and source all components, systems, and fuel entirely through existing commercial nuclear supply networks.
The physical facility was engineered for extreme construction speed, completing the primary build phase in just 229 days. Large-scale components are built off-site and transported directly to the Lockhart, Texas footprint, acting as a blueprint for modular deployment.
“When the Administration issued its Executive Order calling for multiple advanced reactors to go critical outside the national laboratories, it challenged the industry to demonstrate a new way forward,” said Oklo co-founder and CEO Jacob DeWitte. “Groves is that demonstration. It is the first advanced reactor project to receive approval of its Documented Safety Analysis that is on privately owned land, with wholly commercially sourced fuel, equipment, and systems delivered by the private sector.”
He added: “With approval of both the Preliminary and Documented Safety Analyses, Groves now moves into the final phase before startup, including readiness review, fuel loading, and criticality,” DeWitte added. “Less than a year after breaking ground, Groves is advancing toward criticality and demonstrating that advanced nuclear can move from an open field to deployment on a commercial timeline and with a commercially representative facility. DOE demonstrated remarkable capabilities to review and reach this milestone for a facility of this type, and for a facility outside of a national laboratory on this timescale.
Oklo is executing a dual-track regulatory strategy. Rather than risking its entire corporate timeline on a single, lengthy federal pathway, Oklo leverages the DOE authority for pilot deployments on federal land (and specific test sites) while simultaneously advancing broad commercial licensing with the Nuclear Regulatory Commission (NRC). The Groves VIPR and the Aurora Powerhouse represent two completely distinct engineering philosophies, tailored for entirely separate end-use markets.
Following an initial procedural setback in 2022, Oklo overhauled its approach. In January 2022, NRC issued a rare, formal denial of Oklo’s Combined Licence Application (COLA) to build and operate its first Aurora powerhouse at INL. NRC stated that the denial was not based on a finding that the Aurora reactor was unsafe. Instead, it was a procedural rejection due to a lack of technical information.
According to the regulatory review, Oklo failed to provide sufficient data on several key topics required for a full safety assessment. These included: maximum credible accident scenario; clear safety classifications for various reactor components; and the foundational programmatic requirements of the novel fast-reactor design.
Rather than appealing the decision, Oklo adopted a roadmap to restructure its regulatory strategy. Oklo officially restarted the licensing process in September 2022, shifting to a rigorous “pre-application phase” with NRC. To prevent another comprehensive bottleneck, Oklo began submitting specific technical sections individually. Securing separate, early approvals for these “Topical Reports”, such as its Principal Design Criteria (PDC), allowed the company to iron out regulatory disagreements step-by-step.
The company has achieved several accelerated milestones under updated federal laws such as the ADVANCE Act. NRC officially approved the PDC topical report for the Aurora Powerhouse in May. The PDC serves as the formal “regulatory blueprint” that defines the fundamental safety, reliability, and performance boundaries for the reactor. By locking this in early, Oklo drastically reduces regulatory risk, as the NRC will not need to re-review these core baseline engineering choices during individual plant applications. Reflecting recent regulatory modernisations, NRC accepted the final report for review in just 15 days instead of the customary 60 days.
While Oklo broke ground on early infrastructure at the Idaho National Laboratory site under DOE’s site agreements, it continues NRC pre-application engagement to lock in the final operating framework. Oklo is actively translating the technical data, component classifications, and principal design criteria vetted during its Idaho National Laboratory (INL) regulatory track to move its upcoming commercial project in Ohio into the formal Combined Licence Application (COLA) stage. In this way, Oklo can significantly compress the licensing timeline for its commercial deployments.
Unlike the single 15 MWt test reactor in Texas or the initial units in Idaho, the Ohio project aims to deliver 1.2 GWe of nuclear energy. In early 2026, Oklo signed a landmark agreement with Meta Platforms to support the technology firm’s regional data centres and massive AI supercluster operations.
The Groves site in Texas bypassed NRC entirely by concluding its safety reviews under the DOE RPP. However, Oklo’s long-term business plan includes taking the operating experience gained from the Texas site to build a fleet of up to four additional NRC-approved commercial VIPR systems for the broader medical sector.
