Zeno Power to make nuclear batteries at historic California site

Zeno Power is moving nuclear batteries out of the concept stage and into a production line at Vallecitos Nuclear Center, a 1,600-acre California site that helped define early U.S. commercial nuclear power. The Seattle company said it will build an end-to-end manufacturing facility there, restoring specialized hot cell infrastructure so it can receive, store, process, assemble, test and integrate radioisotope power systems on one site.

The first product line is already taking shape. Zeno said it is initially focusing on strontium-90-fueled nuclear batteries for undersea applications, while also building toward space missions and other extreme-environment uses. The company said nonradiological operations have already started at Vallecitos, with radiological operations expected later in the year pending regulatory approval. Zeno also said it is preparing full-scale demonstrations in 2026, with first systems still on track for delivery in 2027 and scaled production beginning in 2028.

That push is backed by a real customer base, not just a pitch deck. Zeno said it has more than $60 million in active U.S. government contracts with NASA and the Department of Defense, plus follow-on demand from government and commercial customers. The company’s timing also tracks with a recent technical milestone: on April 21, 2026, Zeno said it completed a Final Design Review for its space nuclear battery under NASA’s Harmonia Radioisotope Power System for the Artemis Tipping Point program, and said the design delivered 3.5 times the originally specified power output.

Vallecitos brings more than empty floor space. The U.S. Department of Energy says the site was used for Atomic Energy Commission and civilian nuclear industry research from 1965 through 1975, and the Vallecitos boiling water reactor operated there from 1957 to 1963. The reactor, a 24 MWe unit, was the first privately owned nuclear power plant to deliver significant quantities of electricity to a public grid, and ASME says it generated about 40,000 megawatt-hours over its operating life.

NorthStar, which acquired the Vallecitos Nuclear Center through a transfer agreement announced in 2023 and closed in 2025, said decommissioning work is ahead of schedule and on budget for completion by 2026. For Zeno, that matters because the company is not trying to brand a future reactor. It is repurposing licensed nuclear infrastructure into a factory that will make actual radioisotope power systems, and that is the difference between a hobbyhorse and a production base.