Oklo cleared to start up test reactor

Oklo cleared to start up test reactor - World Nuclear News

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Friday, 24 July 2026

The US Department of Energy has granted authorisation to nuclear technology company Oklo to start up its Groves Isotope Test Reactor, located near Lockhart in Caldwell County, Texas.

Groves Isotope Test Reactor facility (Image: Oklo)

This authorisation, granted under department's Reactor Pilot Program, completes the Department of Energy (DOE) authorisation process and clears the way for fuel loading, startup testing, and reactor operations. The authorisation followed a rigorous readiness review, through which DOE confirmed that Oklo has achieved the engineering, organisational, and operational readiness needed to safely receive fuel and begin reactor operations.

The Reactor Pilot Program, announced in June 2025, aims to expedite the testing of advanced reactor designs that will be authorised by the DOE at sites located outside of the national laboratories. Part of the Reforming Nuclear Reactor Testing at the Department of Energy executive order signed by President Donald Trump in May last year, its goal is "to construct, operate, and achieve criticality of at least three test reactors using the DOE authorisation process by July 4, 2026".

Antares Nuclear's Mark-0 reactor became the first reactor under the programme to reach initial criticality in early June, closely followed by Valar Atomics' Ward 250 reactor. Deployable Energy's Unity demonstration reactor achieved criticality on 1 July, while Aalo Atomics' Critical Test Reactor chieved initial criticality in the early hours of 4 July.

Groves is a low-power test reactor designed to demonstrate reactor design, build, and operations, and to establish operating experience needed to support future isotope production facilities. The project advances Oklo's plans to establish domestic production of critical isotopes for potential use in cancer care, manufacturing, scientific research, space exploration, and national security.

A privately financed facility, Groves was built on private land, including full-scale civil excavation and construction, and assembled with all full-scale systems, components, and fuel either sourced commercially or manufactured by Oklo.

"This facility marks the fastest time that we are aware of to go from greenfield to substantial completion for a full-scale, privately funded and sited reactor in history," said Oklo co-founder and CEO Jacob DeWitte. "By building on a greenfield site on private land, performing full-scale civil excavation and construction, and procuring fuel and all major components commercially, we demonstrated that the advanced nuclear industry can move at a pace that many did not believe possible. And this experience is fully translatable to future commercial deployments."

Principal Deputy Assistant Secretary for Nuclear Energy Mike Goff added: "The US Department of Energy is excited to see another Reactor Pilot Program participant receive authorisation. With the right enabling environment, Oklo has been able to accelerate their progress and is now ready to take the next step with their technology."

Oklo cleared to start up test reactor

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