Somewhere beneath the hills of Oak Ridge, Tennessee — the birthplace of America's first nuclear reactors during the Manhattan Project — a new chapter in atomic energy is being written. Kairos Power announced on Monday that Samsung C&T, the engineering and construction arm of South Korea's Samsung conglomerate, will co-build its 50-megawatt Hermes 2 demonstration reactor, a project ultimately destined to supply electricity to Google's data centres. The deal is valued at up to $100 million, of which $70 million takes the form of a direct equity stake, giving Samsung C&T a financial reason to see the project succeed, not merely a contractual one. The reactor at the heart of this partnership is no ordinary design.

Hermes 2 will use fluoride salt as a coolant rather than the pressurised water found in conventional plants. Because fluoride salts boil at extremely high temperatures, the system operates at low pressure, which significantly reduces the risk of the kind of catastrophic blowouts that have haunted nuclear energy's public reputation for decades. The fuel, too, is unconventional: tiny uranium seeds wrapped in ceramic and carbon layers, then packed into spheres roughly the size of billiard balls — a configuration known as TRISO that is specifically engineered to prevent meltdowns. Neither technology has yet been proven at commercial scale, which is precisely why this demonstration matters.

The urgency behind the project is driven by a familiar force: artificial intelligence. Google signed its initial agreement with Kairos in late 2024, seeking roughly half a gigawatt of nuclear capacity by 2035 to power the data centres that underpin its AI operations. Samsung C&T has constructed approximately a dozen reactors worldwide, and its involvement is widely seen as a signal that established engineering giants regard this new wave of nuclear startups as commercially serious rather than merely aspirational.