The startup is betting on a retro reactor design, rapid manufacturing, and a sealed-steel approach to redefine nuclear energy’s future
Nuclear’s Renaissance: Why Now?
After years on the fringe, nuclear energy is back in the spotlight—and Last Energy is one of the startups leading the charge.
- The company just closed a $100 million Series C led by the Astera Institute, with participation from AE Ventures, Gigafund, Woori Technology Investment, and others.
- The surge in data center energy demand and clean energy urgency is pushing investors and policymakers to reconsider nuclear as a scalable, carbon-free energy source.
“Everyone just comes to us saying, ‘Of course nuclear is key,’” says CEO Bret Kugelmass, reflecting on the shift in perception.
A Bold, Back-to-Basics Reactor Design
What sets Last Energy apart? Instead of starting from scratch, the company is reviving and re-engineering a proven reactor design—originally used in the NS Savannah, the world’s first nuclear-powered merchant ship.
- That ship’s power plant was one-tenth the size of Last Energy’s new reactor design.
- The startup has scaled and modernized the system to deliver 20 megawatts of electricity—enough to power 15,000 homes.
- The design is based on pressurized water reactor (PWR) tech, a decades-old standard in nuclear power.
By leveraging existing designs and focusing on manufacturability, Last Energy hopes to cut costs and accelerate deployment.
A New Approach: Steel, Not Concrete
Perhaps the most radical shift is the company’s decision to encase each reactor core in 1,000 tons of steel, not concrete.
- The sealed steel reactor is designed to never be serviced during its operational life—minimizing complexity and reducing long-term maintenance risks.
- The reactors arrive fully fueled with six years of uranium. After operating, the entire steel unit becomes a self-contained waste cask.
- Unlike traditional reactors, there are no penetrations through the steel shell, aside from electrical and control interfaces.
“Most people think concrete is cheaper,” Kugelmass said. “But not when it’s nuclear-grade concrete.”
This design reduces the need for on-site construction, one of the biggest sources of delays and cost overruns in traditional nuclear projects.
Building the First Units, Scaling for Thousands
Last Energy’s near-term goal is to build a 5-megawatt pilot reactor at Texas A&M, fully funded by the new raise.
- The pilot reactor is expected to come online in 2026, with the full 20-megawatt version slated for 2028 production.
- The long-term vision? Mass production. The company believes it can scale to thousands of units, with significant cost reductions following the kind of economies of scale seen in other tech sectors.
While Kugelmass won’t commit to exact pricing, he points to price compression trends in other industries—such as solar and semiconductors—where costs fall dramatically with scale.
“We don’t think in ones and twos,” he said. “We think in tens of thousands.”
Micro Reactors, Mega Potential
Last Energy joins a growing list of nuclear startups securing big checks:
- X-energy raised $700M (backed by Google).
- Aalo Atomics brought in $100M for its prototype.
- Antares raised $96M for its next-gen reactor design.
Yet while most nuclear startups chase advanced fission concepts, Last Energy’s strength lies in simplifying, not reinventing. It’s shipping proven tech, wrapped in modern engineering and AI-driven manufacturing workflows.
If successful, the company could make small nuclear reactors as scalable as shipping containers—deployable anywhere, affordable for industrial or grid use, and with zero-emission output.
