Nuclear start-up Oklo said Wednesday that its isotope test facility had passed its final safety analysis, capping off months of uncertainty over whether the company would get a reactor running in line with the government's timeline.

Oklo was selected last year for an Energy Department initiative to deploy at least three test reactors at national laboratories by July 4. With its safety analysis complete, the company confirmed it was on track to achieve first criticality for the Groves nuclear reactor this month.

Moving forward, Oklo aims to use its Groves facility to lay the groundwork for a steady supply of high-value radioisotopes, which can be used in medicine and manufacturing. The U.S. historically has relied on aging facilities overseas to supply the bulk of its isotopes.

Still, the biggest challenge remains: bringing a commercial reactor online fast enough to satisfy investors. Unlike Oklo's larger Aurora designs, the Groves reactor doesn't generate electricity. The start-up has been laying the groundwork for its first Aurora powerhouse on the grounds of Idaho National Laboratory, where it is also building a fuel fabrication facility.

For now, a test reactor is a start. Wall Street was cheering the progress, as Oklo shares spiked 5% in premarket trading. Futures tracking the benchmark S&P 500 were slightly lower.

Write to Mackenzie Tatananni at mackenzie.tatananni@barrons.com

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July 01, 2026 07:36 ET (11:36 GMT)

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