The nuclear energy sector is experiencing a financial surge reminiscent of the early days of the AI boom, with Radiant Nuclear becoming the latest beneficiary of a high-stakes investment wave.
Just one day after Last Energy announced a $100 million raise, Radiant disclosed a massive $300 million Series D funding round, valuing the startup at more than $1.8 billion. Led by Draper Associates and Boost VC, and supported by heavyweights like Chevron Technology Ventures and Founders Fund, the deal underscores a frantic rush to secure future energy supplies for a power-hungry world.
This influx of capital is part of a broader pattern of “eye-popping” fundraises. In the last three months alone, the sector has seen X-energy raise $700 million and Aalo Atomics secure $100 million. For Radiant, this round follows a $165 million Series C just six months ago, signaling that investors are no longer satisfied with slow-moving research; they are now funding the transition to industrial-scale mass manufacturing.
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The AI Power Crisis: Why Data Centers are Going Nuclear
The primary catalyst for this “frothy” market is the relentless expansion of Artificial Intelligence. Data centers and developers are facing a looming electricity shortfall, leading them to look beyond the grid for dedicated, “behind-the-meter” power sources.7 Radiant has already capitalized on this trend, signing a landmark deal with global data center leader Equinix to supply 20 of its microreactors.
While many nuclear startups are aiming for large-scale utility plants, Radiant is focusing on the microreactor—a compact, modular unit that can be deployed quickly and autonomously. This strategy appeals directly to data center operators who need reliable baseload power to feed dense GPU clusters without the decade-long wait times associated with traditional nuclear facilities.
Kaleidos: A Portable Powerhouse Designed for the Modern Edge
Radiant’s flagship technology is the Kaleidos, a high-temperature gas-cooled microreactor designed to produce 1 MW of electricity and up to 1.9 MW of thermal power. Unlike traditional reactors that rely on vast quantities of water for cooling, Kaleidos is helium-cooled and uses fans for air-to-air heat exchange. This “waterless” design allows it to operate in remote desert environments, disaster zones, or military outposts where traditional cooling is impossible.
The safety of the Kaleidos rests on its use of TRISO (Tri-structural Isotropic) fuel. These are tiny poppy-seed-sized kernels of uranium enriched with carbon and ceramic-coated layers. These layers act as a containment vessel for each individual grain of fuel, making it virtually meltdown-proof. The fuel can withstand temperatures that would melt traditional reactor cores, ensuring that if cooling is lost, the reactor naturally sheds heat without releasing radiation.
A critical differentiator for Radiant is its move toward mass production. The company is breaking ground on its R-50 factory in Oak Ridge, Tennessee, aiming to eventually produce up to 50 reactors per year. The core philosophy is that fission will only become cost-competitive with diesel if reactors are built on assembly lines rather than as “first-of-a-kind” artisanal construction projects.
The Kaleidos unit is designed to fit entirely within a standard 8×20-foot shipping container, allowing it to be delivered via semi-truck or aircraft and activated overnight. Radiant’s business model reflects this flexibility: customers can purchase the units outright or enter into Power Purchase Agreements (PPAs). At the end of a reactor’s 20-year lifespan, Radiant simply hauls the unit away, removing the burden of nuclear waste management from the site owner.
The 2026 Criticality Sprint and the Bubble Risk
Radiant is currently in a high-speed regulatory sprint. The company is one of 11 selected for the U.S. Department of Energy’s Reactor Pilot Program, which is racing toward a goal set by the Trump administration: to have at least three advanced reactors achieve criticality—a self-sustaining nuclear reaction—by July 4, 2026.
Testing for Radiant’s demonstration unit is scheduled to begin in the Summer of 2026 at the Idaho National Laboratory’s DOME (Demonstration of Microreactor Experiments) facility. This will be the first time a new commercial reactor design has been tested in the facility in over 50 years.
However, the rapid influx of cash raises the specter of a market bubble. If these startups fail to meet their 2026 milestones or if the transition from “hand-built” demonstration units to “factory-mass-produced” units stumbles, a significant winnowing of the field is likely. The coming two years will determine whether this is the dawn of a nuclear golden age or a speculative fever that outpaced the technical reality of building hard infrastructure.