DOE clears Oklo's Groves reactor for fuel loading and first criticality in Lockhart, Texas

The U.S. Department of Energy granted startup authorization to Oklo for its Groves Isotope Test Reactor in Lockhart, Texas on 23 July 2026, clearing the way for fuel loading, startup testing, and first criticality at the facility located roughly 30 miles south of Austin.^[1]

What the authorization covers

The authorization, granted under the DOE's Reactor Pilot Program, completes the department's authorization process and clears the way for fuel loading, startup testing, and reactor operations. The startup authorization followed a rigorous readiness review through which DOE confirmed that Oklo had achieved the engineering, organizational, and operational readiness needed to safely receive fuel and begin reactor operations - a multidisciplinary evaluation covering facility procedures, personnel training, equipment conformance to approved design, safety equipment function, and required safety management programs.

Oklo fully developed these safety management programs in-house rather than relying on an established or pre-existing operating framework within an established facility such as a national laboratory.

The reactor itself

Groves is a pool-type, water-cooled, non-pressurized reactor using low-enriched uranium fuel. It is not designed around large-scale steam generation, high-pressure operation, or commercial electricity production. The reactor's rated thermal capacity is 15 MWth.^[1]

In just over 10 months, Oklo progressed from groundbreaking to receiving DOE startup authorization - during that period building the reactor facility, establishing the operating organization, qualifying personnel, implementing nuclear programs and procedures, procuring fuel and major equipment from commercial suppliers, and completing the DOE authorization process.

Why it matters: isotope production, not electricity

The Groves low-power test reactor will demonstrate reactor operations that support Oklo's plans for commercial-scale domestic isotope production. The facility is operated by Atomic Alchemy, Oklo's wholly owned subsidiary, which signed an Other Transaction Agreement with DOE on 7 January 2026 establishing a framework for execution and risk reduction to design, construct, and operate the first radioisotope pilot plant under the DOE Reactor Pilot Program.

Atomic Alchemy's reactor was one of 11 projects selected for DOE support under the Reactor Pilot Program, which was established by President Trump's May 2025 Executive Order 14301, Reforming Nuclear Reactor Testing at the Department of Energy.

The longer-term commercial target is a multi-reactor foundry. The foundry is planned to include up to four non-power VIPR systems with a capacity of around 15 MWth each. The Groves reactor is designed to produce high-value isotopes for cancer treatment and space exploration. The facility is intended to be vertically integrated - the VIPR creates the raw isotopes, and an adjacent radiochemistry laboratory refines them into medical-grade products on the same campus, addressing the "decay problem" where short-lived isotopes lose their potency during long-distance shipping.

What to watch

First criticality - the point at which the reactor sustains a controlled, self-sustaining nuclear chain reaction - was Oklo's stated target for July 2026.^[1] Whether that date held will be confirmed when Oklo reports startup testing results. The more consequential near-term signal is whether Groves generates the operating data needed to accelerate permitting for the full VIPR foundry - and whether the DOE Reactor Pilot Program pathway, which has not yet taken any reactor from authorization to criticality, proves replicable at speed for the other 10 selected projects.