Los Alamos microreactor clears key criticality milestone

Los Alamos National Laboratory’s ZiaCore microreactor achieved zero-power criticality in April and May 2026 at NCERC, a benchmark that validates the reactor’s design and fuel strategy. The milestone bolsters New Mexico’s advanced nuclear profile as industry leaders prepare to meet in Los Alamos on Aug. 25.

Why it matters: - ZiaCore’s criticality demonstration validates the reactor physics behind a U.S. microreactor design aimed at reliable, carbon-free power. - The fuel approach could matter for deployment because ZiaCore is designed to use commercially available low-enriched uranium today and transition to HALEU as domestic production expands. - That flexibility addresses one of the advanced reactor sector’s biggest bottlenecks: limited HALEU supply. - The milestone adds momentum for advanced reactors that could support national security, artificial intelligence, data centers, advanced manufacturing, critical infrastructure and remote communities.

What happened: - Los Alamos National Laboratory completed a zero-power criticality demonstration of the ZiaCore™ microreactor at the National Criticality Experiments Research Center in April and May 2026. - The New Mexico Nuclear Alliance publicly congratulated LANL and Christopher Stanek, director of Nuclear Energy Programs, on the result. - The demonstration ran over four weeks and reached high-temperature, zero-power criticality. - The achievement puts ZiaCore among a growing group of advanced microreactor technologies from national laboratories and private industry that have successfully achieved criticality.

The details: - The demonstration served as a benchmark for reactor development and confirmed the ZiaCore design performed as intended. - ZiaCore’s fuel strategy uses LEU now and can shift to HALEU later as U.S. production scales. - Scott Lopez, founder and CEO of the New Mexico Nuclear Alliance, said the result shows the kind of innovation needed to strengthen energy security and technological leadership. - Lopez said New Mexico plays a unique role across the nuclear enterprise, from uranium production and fuel development to reactor research, nuclear medicine, transportation, waste management, environmental stewardship, commercialization, financing, workforce development and RECA-related recognition of uranium workers, downwind communities and Tribal nations. - Lopez said collaboration across national labs, universities, Tribal communities, private industry, utilities, entrepreneurs, investors, environmentalists, regulators and policymakers is helping build a stronger energy future.

Between the lines: - The ZiaCore result is as much about fuel logistics as it is about reactor physics. - A design that can start with LEU could lower near-term deployment friction while the industry waits for broader HALEU availability. - New Mexico is using the milestone to reinforce its claim as a full-spectrum nuclear hub, not just a research site. - The timing also builds attention for the inaugural Los Alamos Nuclear Forum, where the advanced reactor ecosystem will gather to discuss deployment, fuel security and financing.

What's next: - The inaugural Los Alamos Nuclear Forum is set for Aug. 25, 2026, in Los Alamos, New Mexico. - Christopher Stanek will deliver the opening keynote and moderate the advanced reactor deployment discussion. - Participants will include leaders from the U.S. Department of Energy, NEI, LANL, Sandia National Laboratories, WIPP, advanced reactor developers, uranium producers, fuel cycle companies, utilities, investors, entrepreneurs, universities, Tribal communities and New Mexico policymakers. - Forum discussions will focus on advanced reactor deployment, domestic fuel security, AI and data center demand, financing and investment, workforce development, waste management, long-term stewardship and the New Mexico Nuclear Innovation Showcase. - Media registration, credentials and the full agenda are available at Los Alamos Nuclear Forum. - Participating organizations include Antares Industries, the CLEAN Energy Association of New Mexico, DISA USA, Eden Radioisotopes, Geosyntec Consultants, Grants Energy, Kit Carson Electric Cooperative, Laramide Resources, Los Alamos County, the National Museum of Nuclear Science & History, the New Mexico Renewable Energy Transmission Authority, New Mexico Tech, NewSpace Nexus, Oklo, the Regional Development Corporation, Space Nuclear Corporation, UNM-Los Alamos, Verdera Energy, Waste Control Specialists and Westinghouse.

The bottom line: - ZiaCore’s criticality mark is a technical win for advanced nuclear and a strategic signal for New Mexico’s role in the U.S. nuclear supply chain.