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yesterday

Valar Atomics' Ward 250 Reaches Zero‑Power Criticality in Utah

DOE confirmation of the June 18 test validating the reactor’s physics launches Valar’s power‑ascension experiments with a target to make power before July 4.

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Ward 250 nuclear reactor
The 452nd Logistics Readiness Squadron Aerial Port Flight support loading operations of the Valar Atomics Ward 250 reactor onto a C-17 Globemaster III at March Air Reserve Base, Calif., Feb. 15, 2026. The mission, called "Operation Windlord," marked the first military airlift of a microreactor and transported the Ward 250 to Hill Air Force Base, Utah, en route to the San Rafael Energy Lab test site. Courtesy: Valar Atomics
Jess Housekeeper, director of Utah operations for Valar Atomics, shows the top of the reactor as work continues on the facility at Valar Atomics in Orangeville on Tuesday, March 10, 2026, for a small modular reactor.

Overview

  • DOE confirmed on June 18 that Valar Atomics’ Ward 250 achieved zero‑power fueled criticality at the San Rafael Energy Lab in Emery County, Utah.
  • The Ward 250 milestone is the second criticality under the DOE Reactor Pilot Program after Antares’ Mark‑0 and is the first DOE‑authorized reactor built and operated outside the national laboratory system.
  • Ward 250 is a Gen IV, helium‑cooled high‑temperature gas reactor using TRISO fuel and completed zero‑power testing as a complete, integrated system configured for later power operations; zero‑power criticality shows the core can sustain a chain reaction at negligible heat output.
  • Valar has begun non‑commercial power‑ascension experiments and says it is aiming to generate power before July 4, while wider deployment will require further testing, Nuclear Regulatory Commission licensing, and scaling of TRISO/HALEU fuel and manufacturing.
  • The result advances the DOE’s accelerated Reactor Pilot Program created under Executive Order 14301 and follows rapid project steps such as a military airlift of components in February and prior physics validation at Los Alamos, but the path to commercial electricity and broader public benefits remains dependent on regulatory and supply‑chain milestones.