US startup hits key nuclear milestone with help from Los Alamos lab

Valar Atomics, a nuclear startup based in El Segundo, has achieved a significant milestone by reaching criticality—a controlled, sustained nuclear fission reaction—marking the first time a U.S. nuclear startup has done so. This achievement was made possible through collaboration with Los Alamos National Laboratory, which provided structural components and supported fuel testing. The criticality achieved was "cold" or zero-power, meaning the reactor sustained the chain reaction without producing heat or electricity, serving primarily to validate reactor design and fuel geometry. Valar’s founder, Isaiah Taylor, emphasized that this milestone signals a new era in American nuclear engineering characterized by rapid development and closer federal-private sector partnerships. This breakthrough is part of a broader Department of Energy (DOE) pilot program aimed at accelerating nuclear innovation by allowing startups to bypass the traditionally lengthy Nuclear Regulatory Commission (NRC) approval process for criticality tests. The program, initiated under the Trump administration and continuing with DOE support, enables research reactors to be developed under a research