Today, as part of the U.S. Department of Energy Reactor Pilot Program, Valar Atomics’ advanced reactor design, Ward 250, successfully completed a zero-power fueled criticality demonstration.
Energy.gov June 18, 2026
WASHINGTON—The U.S. Department of Energy (DOE) today celebrated another historic milestone in America’s nuclear renaissance. DOE Reactor Pilot Program participant Valar Atomics’ advanced reactor design, Ward 250, successfully completed a zero-power fueled criticality demonstration. The experiment took place at the Utah San Rafael Energy Lab in Emery County, Utah, and marks the first DOE authorized reactor built outside of a national laboratory.
“Today marks another historic moment for America’s nuclear renaissance,” said U.S. Energy Secretary Chris Wright. “From the first-ever airlift of a small reactor aboard a U.S. military C-17 to successful zero-power criticality testing, Valar Atomics is delivering achievements that mark a revolutionary moment for advanced nuclear in this country. The Trump administration is proud to support the rebirth of America’s nuclear industry, ensuring Americans have access to affordable, reliable and secure energy for generations to come.”
Ward 250 is the second of multiple advanced reactors anticipated to go critical by the July 4th deadline set by President Trump in his May 2025 executive order. Criticality demonstrates that Ward 250 can sustain a controlled nuclear chain reaction, which must be achieved before the reactor can generate power. Earlier this month, Antares Nuclear’s Mark-0 reactor achieved criticality at Idaho National Laboratory.
“Nine months ago, this was an empty site. Today, there’s a critical reactor on it, built and operated by the Valar team,” said Isaiah Taylor, Founder & CEO of Valar Atomics. “We met the milestone the executive order set. This reactor was built to make power, and that’s exactly where we’re headed. I’m grateful to the Department of Energy, the State of Utah, the local community, and the many people who got us here.”
The Department’s Reactor Pilot Program has catalyzed rapid innovation and progress in furthering American advanced reactor designs. The Reactor Pilot Program leverages DOE authorization to expeditiously certify and construct first-of-a-kind advanced reactor designs for demonstration. Building on the Reactor Pilot Program’s success, DOE recently established the Nuclear Energy Launch Pad to further accelerate the deployment of advanced nuclear technologies.
Learn more about the Reactor Pilot Program.
###
