Helion has raised $465 million in a Series G led by Thrive Capital, valuing the company at $15.5 billion.

Helion Energy, a nuclear fusion startup backed by OpenAI’s Sam Altman, still has to prove it can produce electricity to serve data centers and other customers. But investors seem…

Fusion startup Helion is racing to complete a power plant for Microsoft by 2028. A fresh infusion of cash should help with that.