Nuclear startup Oklo splits its first atoms in test reactor

Oklo, a nuclear startup backed by OpenAI's Sam Altman, has run its first successful chain reaction, known as achieving criticality, at a test reactor in rural Caldwell County, Texas. The reactor isn't meant to generate electricity for homes. It's a demonstration unit for a new medical isotope business, though Oklo says the work will also help its longer-term push to build power-generating reactors.

This is a step forward, not a sign that new nuclear power is coming to anyone's neighborhood soon. Oklo is one of several small-modular-reactor companies working through a Department of Energy pilot program, and it's now the fifth of ten companies in that program to reach criticality in the past two months. But Oklo still doesn't have federal approval to build its actual power-generating reactor design. Its 2022 application was rejected by the Nuclear Regulatory Commission, and it has not yet resubmitted. Right now, only two similar startups, TerraPower and Kairos, are actively building power reactors in the U.S. Oklo is separately preparing a site near a national lab in Idaho for its first reactor, but hasn't gotten permission to start building it.

For homeowners, this news doesn't change anything about your options for solar, heat pumps, or other home energy upgrades today. It's a marker of how far next-generation nuclear technology has come, not a new source of power on the grid. Advanced reactors like this one remain years away from supplying electricity to homes, if they get there at all.