US Nuclear Pilot Program Hits Second Milestone as Valar Atomics Achieves Reactor Criticality

The push to commercialize next-generation nuclear energy has crossed a major threshold. Valar Atomics, a Southern California-based energy startup, successfully achieved "zero-power fueled criticality" with its Ward 250 advanced reactor design at the Utah San Rafael Energy Lab.[1][2]

The milestone means the reactor successfully sustained a controlled nuclear chain reaction of uranium-235—the fundamental physical process required to generate nuclear power. Because it was a "zero-power" test, the reactor did not reach full operating temperatures or generate electricity, allowing engineers to safely verify the core's neutron physics and fuel performance before scaling up.[2][5]

Valar's achievement marks the second major breakthrough under the US Department of Energy's (DOE) Reactor Pilot Program. Earlier in June, Antares Nuclear reached criticality with its Mark-0 microreactor at the Idaho National Laboratory, kicking off a rapid succession of industry wins.[1][2][6]

The DOE program, established by a May 2025 executive order, is designed to aggressively accelerate nuclear innovation. It mandates that at least three advanced test reactors achieve criticality by July 4, 2026—the nation's 250th anniversary.[4][6]

To meet this ambitious timeline, the pilot program allows participating companies to bypass the traditional, often decades-long licensing process of the Nuclear Regulatory Commission (NRC). Instead, the reactors are authorized directly by the DOE and built outside of federal national laboratories, dramatically reducing bureaucratic friction.[3][4]

Valar Atomics' Ward 250 is a high-temperature gas-cooled reactor (HTGR) that uses helium as a coolant and relies on TRISO fuel. This robust, next-generation uranium fuel is encased in carbon and ceramic layers, making it virtually impossible to melt down even under extreme heat.[5][7]

The reactor is designed to be highly modular and transportable. In February 2026, the US military demonstrated this capability by airlifting the 5-megawatt Ward 250 unit—without its nuclear fuel—on a C-17 Globemaster III cargo plane from California to Hill Air Force Base in Utah.[3][6]

Once fully operational, a single 5-megawatt reactor could generate enough electricity to power approximately 5,000 homes. However, Valar's ambitions extend far beyond residential power grids.[3][6]

The company's founder and CEO, Isaiah Taylor, envisions deploying hundreds of these reactors at centralized "Gigasites." Because HTGRs operate at extremely high temperatures (above 750°C), they can provide direct industrial heat for processes that are notoriously difficult to decarbonize, such as steel manufacturing, hydrogen production, and synthetic fuel synthesis.[5][7]

The tech industry is also closely watching the pilot program. As artificial intelligence models demand exponentially more computing power, tech giants are increasingly looking to small modular reactors to provide reliable, grid-independent, zero-carbon electricity for massive new data centers.[4][7]

Energy Secretary Chris Wright celebrated the Utah test as a historic moment for America's "nuclear renaissance," framing the rapid development cycle as proof that domestic startups can outpace international competitors in the clean energy race.[2][6]

However, the fast-tracked approach has drawn scrutiny. Nuclear safety advocates caution that bypassing the NRC's rigorous oversight in favor of rapid DOE authorization could introduce unforeseen risks, arguing that speed should not eclipse the industry's historical safety standards.[6]

Despite the skepticism, the momentum behind the DOE's pilot program is accelerating. With two reactors now having achieved criticality, the federal government is well on its way to meeting its July 2026 mandate, potentially ushering in a new era of decentralized, carbon-free industrial power.[2][4]