Nuclear startup Last Energy raises $100M for its steel-encased micro reactor

After years in the wilderness, it’s a good time to be a nuclear startup. “For the first half a decade that I was telling people I was doing nuclear, I had to convince them, ‘Hey, here’s why nuclear is important,’” Bret Kugelmass, founder and CEO of Last Energy, told TechCrunch. “Now everyone just comes to us saying, ‘Oh yeah, of course nuclear is a key part of the solution.’ I’m like, okay, great, I’m glad everyone’s caught up now.” Last Energy is building small modular reactors — compact nuclear power plants that can be mass-manufactured to reduce costs. The company’s reactors are designed to produce 20 megawatts of electricity, enough to power roughly 15,000 homes. It has momentum. Last Energy just closed a $100 million Series C led by the Astera Institute with participation from AE Ventures, Galaxy Fund, Gigafund, JAM Fund, The Haskell Company, Ultranative, Woori Technology, and others. The company joins a slew of nuclear startups that have raised funding in recent months, buoyed by data centers’ insatiable power demands. Google-backed X-Energy raised $700 million last month, while Antares raised $96 million two weeks ago. And in August, Aalo Atomics raised $100 million to build its prototype reactor. What sets Last Energy apart from competitors is its approach: the company is using an old reactor design developed by the government decades ago. The initial design for the pressurized water reactor was built for the NS Savannah, the world’s first nuclear-powered merchant ship. That ship’s power plant was about one-tenth the size of Last Energy’s planned commercial reactor. Kugelmass said the company’s updated design should produce 20 megawatts of electricity. The company is starting smaller, though. First, Last Energy is building a 5-megawatt pilot reactor at a site it’s leasing from Texas A&M. The new funding will fully fund the pilot project and help the company start delivering its first commercial products, Kugelmass said. Last Energy hopes to turn on the pilot reactor next year, with its 20-megawatt commercial-scale unit entering production in 2028. Techcrunch event Join the Disrupt 2026 Waitlist Add yourself to the Disrupt 2026 waitlist to be first in line when Early Bird tickets drop. Past Disrupts have brought Google Cloud, Netflix, Microsoft, Box, Phia, a16z, ElevenLabs, Wayve, Hugging Face, Elad Gil, and Vinod Khosla to the stages — part of 250+ industry leaders driving 200+ sessions built to fuel your growth and sharpen your edge. Plus, meet the hundreds of startups innovating across every sector. Join the Disrupt 2026 Waitlist Add yourself to the Disrupt 2026 waitlist to be first in line when Early Bird tickets drop. Past Disrupts have brought Google Cloud, Netflix, Microsoft, Box, Phia, a16z, ElevenLabs, Wayve, Hugging Face, Elad Gil, and Vinod Khosla to the stages — part of 250+ industry leaders driving 200+ sessions built to fuel your growth and sharpen your edge. Plus, meet the hundreds of startups innovating across every sector. San Francisco | October 13-15, 2026 WAITLIST NOW Last Energy’s startup’s reactor isn’t designed to be serviced during its lifetime. Instead, Last Energy is permanently encasing each core in 1,000 tons of steel. Kugelmass estimates the metal will cost around $1 million. “Most people think concrete is cheaper,” he said. “But not when it’s nuclear-grade concrete.” The reactors will arrive on site fueled with six years’ worth of uranium. Apart from electrical and control connections, there are no other penetrations that break the steel wall. Heat from the fission reactions warms the steel, and water flowing through pipes on the outside harvests that heat to spin a steam turbine. When the reactor’s time is up, Last Energy will leave it on site, with the steel chamber serving as the waste cask, eliminating the need for separate disposal. The hope is that this approach, coupled with manufacturing advances, will drive down the price of nuclear power. Kugelmass wouldn’t commit to a price, instead pointing to other industries that have halved prices for every tenfold increase in production. “I don’t think it’s going to be that good in nuclear because there are always some extra fixed costs that you have in nuclear regarding some of the special regulations, but that’s the type of trend you can see,” he said. “We don’t think in ones and twos, we think in tens of thousands.” Topics Climate, data centers, Fundraising, nuclear fission, nuclear power Tim De Chant Senior Reporter, Climate Tim De Chant is a senior climate reporter at TechCrunch. He has written for a wide range of publications, including Wired magazine, the Chicago Tribune, Ars Technica, The Wire China, and NOVA Next, where he was founding editor. De Chant is also a lecturer in MIT’s Graduate Program in Science Writing, and he was awarded a Knight Science Journalism Fellowship at MIT in 2018, during which time he studied climate technologies and explored new business models for journalism. He received his PhD in environmental science, policy, and management from the University of California, Berkeley, and his BA degree in environmental studies, English, and biology from St. Olaf College. You can contact or verify outreach from Tim by emailing tim.dechant@techcrunch.com.

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