DOE: Ward 250 completed zero-power fueled criticality in Emery County, second under the Reactor Pilot Program
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DOE's June 18, 2026 release says Ward 250 completed a zero-power fueled criticality demonstration at the Utah San Rafael Energy Lab in Emery County, the first DOE-authorized reactor built outside a national laboratory. DOE calls it the second of several reactors expected to go critical by the July 4 deadline in the May 2025 executive order; Antares Nuclear's Mark-0 at Idaho National Laboratory was first earlier that month. Energy Secretary Chris Wright and Isaiah Taylor are quoted; Taylor says the site was empty nine months earlier. DOE describes criticality as a sustained chain reaction that must precede power generation.
In plain termsDOE confirms that on June 18, 2026 Ward 250 in Emery County sustained a chain reaction at essentially zero power, the first step before a reactor makes heat. It was the second reactor to do this under DOE's pilot program. DOE says criticality must be achieved before a reactor can generate power; it shows a sustained chain reaction, not how the reactor performs at power, and it does not settle the separate questions about its safety documents (safe-007).
- Department of Energy Celebrates Second Advanced Reactor Achieving Criticality (U.S. Department of Energy, 2026-06-18) primary government “Nine months ago, this was an empty site.”
- Valar’s Ward 250 reaches criticality in Utah (American Nuclear Society (Nuclear Newswire), 2026-06-22) news
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