Oklo ($OKLO) reached first criticality at its Groves Isotope Test Reactor in Texas, achieving a controlled, self-sustaining nuclear chain reaction under the Energy Department's Reactor Pilot Program. Groves is the fifth reactor to reach the milestone through the program and will support Oklo's plans for domestic isotope production and future commercial reactor deployments.

• The low-power Groves reactor was developed to demonstrate reactor construction, startup and operating capabilities.
• Oklo received DOE startup authorization in July, allowing fuel loading, testing and reactor operations.
• Four projects from Aalo Atomics, Deployable Energy, Antares Nuclear and Valar Atomics previously reached criticality under the program.
• Oklo reported approximately $500,000 in federal lobbying across five filings during the second quarter and about $1.02 million during the first half of 2026.
• Recent filings covered advanced reactor deployment, nuclear fuel recycling and feedstock access, the Nuclear REFUEL Act and DOE appropriations, with contacts including Congress, DOE and nuclear regulators. Additional details are available here.

Relevant Companies

• Oklo ($OKLO) – The milestone advances its isotope-production platform and provides operating experience for future reactor projects.

Editor’s Note: This is a developing story. This article may be updated as more details become available.