Nuclear Startup Last Energy Raises $100M for its Steel-Encased Micro Reactor

After years of convincing people about the importance of nuclear Energy, it’s a good time to be an atomic 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,’” said Bret Kugelmass, founder and CEO of Last Energy. “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.

The startup just closed a $100 million Series C round, led by the Astera Institute with participation from AE Ventures, Galaxy Fund, Gigafund, JAM Fund, The Haskell Company, Ultranative, Woori Technology, and others. This brings Last Energy’s total funding to date to over $150 million.

The funding comes at a time when data centres and other industries have increasing power demands, and Last Energy joins other nuclear startups benefiting from a renewed interest in nuclear Energy. Google-backed X-energy raised $700 million last month, and in August, Aalo Atomics raised $100 million for its reactor prototype.

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 pressurised water reactor was built for the NS Savannah, the world’s first nuclear-powered merchant ship. Kugelmass said the company’s updated design should produce 20 megawatts of electricity.

To start, 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 says the company hopes to turn on the pilot reactor next year, with the 20-megawatt commercial-scale unit entering production in 2028.

The 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 cost of this metal at 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 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 will warm the steel, and water flowing through the outer pipes will capture that heat to drive 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 reduce the cost of nuclear power. Kugelmass wouldn’t commit to a price but pointed 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 regarding special regulations, but that’s the type of trend you can see,” he said.

“I don’t think in ones and twos, I think in tens of thousands,” Kugelmass added.