Valar Atomics Becomes First Ever Nuclear Startup To Achieve Cold Criticality

In the deserts of Nevada, a US startup has achieved cold criticality, a bold step in the development of a functional commercial nuclear reactor. It’s the first time a venture-backed startup has ever done this, and the company argues that its success marks "the dawn of a new era" in the US's efforts to spark a renaissance of nuclear energy. The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.

Valar Atomics, a California-based company, has just announced that its NOVA Core reactor has successfully reached cold criticality. They say the feat was completed on the morning of November 17, 2025, at the Nevada National Security Site operated by Los Alamos National Laboratory.

Criticality occurs when a nuclear reactor sustains a self-perpetuating