Valar Atomics Has Achieved Zero-Power Criticality

Valar Atomics reactor. © Valar Atomics

California-based startup Valar Atomics announced that it has reached zero-power criticality with its new reactor core.

Criticality is the point at which a nuclear reactor can sustain a chain reaction on its own — each atom that splits releases enough neutrons to keep the reaction going.

The milestone was achieved through a partnership between Valar Atomics and Los Alamos National Laboratory (LANL), which supplied facilities and key technology for the test.

Valar Atomics reactor. © Valar Atomics

LANL and Valar Atomics confirmed that the company’s NOVA Core became zero-power critical at the National Criticality Experiments Research Center (NCERC), located at the Nevada National Security Site.

Zero-power criticality, sometimes called cold criticality, is an early but essential step before a reactor produces usable power. At this stage, the uranium-235 in the core sustains a chain reaction, but the reactor stays cool and does not generate significant heat. This allows engineers to study how the core behaves and to confirm design assumptions about the fuel, moderators, control systems, and other materials.

Project NOVA is a joint effort between Valar Atomics and LANL’s NCERC. It involves a series of tests on a reactor core that uses HALEU TRISO fuel (a high-assay, low-enriched uranium fuel known for its strong safety characteristics). The program builds on earlier experiments, including the Deimos assembly in 2024, which helped establish the testing setup now used for NOVA.

Valar Atomics built the central part of the NOVA core, and further experiments over the next few weeks will study how the reactor behaves and how well its high-temperature gas reactor (HTGR) design performs.

For centuries, Western civilization advanced thanks to abundant energy: coal powered the Industrial Revolution, oil enabled worldwide trade, and together they shaped the modern world.