Oklo achieves first criticality at Texas isotope reactor

Oklo Inc. has announced that its Groves Isotope Test Reactor in Lockhart, Texas, achieved first criticality on August 6, 2026. This milestone, representing a controlled and self-sustaining nuclear chain reaction, was reached less than a year after the project broke ground on a greenfield site. The project is noted as the first under the U.S. Department of Energy’s Reactor Pilot Program to reach criticality on privately owned land.

CEO Jacob DeWitte stated that the facility completed substantial construction in 229 days. The Groves reactor is intended to support Oklo’s isotope business, providing materials for healthcare, industry, research, space, and national security. Revenue from the facility is expected to begin in the first half of 2027 via a commercial radiochemistry lab in Idaho.

Financially, Oklo reported a year-to-date net loss of $81.6 million through the second quarter of 2026. Despite this, the company holds $3 billion in cash and marketable securities. Due to increased activity in procurement and construction, Oklo raised its 2026 operating cash flow guidance to between $120 million and $150 million and increased capital expenditure guidance to a range of $400 million to $500 million.