California-based nuclear start-up Valar Atomics and Los Alamos National Laboratory (LANL) announced that NOVA Core has achieved zero-power criticality at LANL’s National Criticality Experiments Research Center (NCERC) at the Department of Energy’s (DOE’s) Nevada National Security Site (NNSS). NCERC provides the test assemblies, instrumentation, and expertise to conduct safe, controlled reactor physics experiments under DOE/NNSA oversight.
The NOVA Core, built by Valar Atomics and operated by LANL on the Comet critical assembly at NCERC, is a graphite-moderated, HALEU TRISO-fuelled nuclear core with boron-carbide control elements in stainless steel. The design builds on the Deimos assembly, incorporating proven structural and measurement components.
NOVA’s configuration was selected to closely model Valar’s Ward250 core. Ward 250 is a high temperature gas-cooled reactor (HTGR) design that uses TRISO fuel, helium coolant and graphite moderators. It aims to build America’s first nuclear gigasites – clusters of thousands of HTGRs designed to produce industrial power and carbon-based fuels cheaper than oil. In September Valar began ground-breaking for a test reactor at the Utah San Rafael Energy Lab (USREL), part of the Utah Office of Energy Development (OED). Valar founder & CEO Isaiah Taylor indicated on X that the Ward 250 will be a 100-kWt reactor.
Zero-power criticality (cold criticality), is a self-sustaining chain reaction of uranium-235 within a nuclear core, but without reaching full operating temperatures or actively removing heat with a working fluid. Zero-power criticality allows Valar to gain a greater understanding of the neutronic characteristics of the core and verify assumptions about fuel, moderators, active reactivity control, and burnable poisons.
Project NOVA (Nuclear Observations of Valar Atomics), a collaboration between LANL NCERC and Valar Atomics, is a series of criticality experiments on a High Assay Low Enriched Uranium Tristructural-isotropic (HALEU TRISO) core. The campaign builds on earlier work at NCERC, including the Deimos critical assembly in 2024, which established the core test geometry and instrumentation approach used as the foundation for NOVA Experiments will continue to evaluate the neutronic behaviour and key performance characteristics of the Ward250 design.
The Ward250 core aims to begin power operations next year under the DOE’s Advanced Reactor Pilot Program, established in line with President Trump’s May Executive Order 14301 with the aim oof having three nuclear startups achieve full criticality by 4 July 2026. NOVA uses the same fuel, moderator, and reactivity-control scheme as Ward250, enabling LANL researchers to collect high-fidelity neutronics data and validate Valar’s physics models ahead of Ward250 power operations.
“Project NOVA provides us with real-world data which will help us answer key questions about TRISO fuel performance in our core and validate our proprietary software stack, which we use to design our power reactors.” said Sonat Sen, Lead Core Designer at Valar Atomics.
“This milestone underscores collaborative efforts propelling nuclear innovation responsibly,” said Dr Rian Bahran, Deputy Assistant Secretary for Nuclear Reactors. “Confirming core physics at zero power with oversight enables Valar’s path to elevated operations, leveraging all DOE capabilities to aid the Reactor Pilot Program’s target of criticality by July 4th and accelerating the AI race via advanced energy generation solutions.”
“Zero power criticality is a reactor’s first heartbeat, proof the physics holds,” said Isaiah Taylor, Founder & CEO, Valar Atomics. “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.”
Valar Atomics raised $130m in a November funding round bringing its total fundraising to $150m. The round was backed by Anduril Industries founder Palmer Luckey and Palantir Chief Technology Officer Shyam Sankar, the company said.
The company, founded in 2023, raised $19m in a seed funding round to develop its first test reactor when it emerged from stealth in February. It has an initial contract with the Philippines Nuclear Research Institute under which it plans to pilot a test-scale reactor and build two full-scale reactors before the first integrated reactor comes online. Valar’s board of directors was recently joined by Doug Philippone, co-founder of Snowpoint and former head of global defence at military surveillance and intelligence company Palantir.
