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. 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 chain reaction of fissionable material. Within the NOVA Core, atoms of uranium-235 were split, releasing neutrons that go on to split more atoms, continuing the reaction like a domino effect. Cold criticality, also called zero-power criticality, refers to a self-sustaining nuclear chain reaction that doesn’t generate enough heat to actually make power. It’s a bit like a test run that allows the engineers to see how the core works without producing enough heat energy to require active cooling or reach full operating conditions. “Zero power criticality is a reactor’s first heartbeat, proof the physics holds,” Isaiah Taylor, Founder and CEO of Valar Atomics, said in a statement. “I’m incredibly proud of the Valar team that took this from blueprint to splitting the atom, securing the first criticality ever achieved by a venture-backed company.” “This moment marks the dawn of a new era in American nuclear engineering — one defined by speed, scale, and private-sector execution with closer federal partnership,” he added.

Full report : Valar Atomics Becomes First Ever Nuclear Startup To Achieve Cold Criticality.

For more see the OODA Company Profile on Valar Atomics.