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

The milestone advances DOE's Reactor Pilot Program toward power‑ascension tests required for commercial licensing.

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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

  • Valar Atomics confirmed that Ward 250 achieved zero‑power fueled criticality on June 18, 2026, demonstrating a self‑sustaining chain reaction at negligible power as part of integrated system testing.
  • The DOE said Ward 250 is the second reactor to hit criticality under its Reactor Pilot Program and the first DOE‑authorized reactor built and operated outside a national laboratory.
  • Valar and CEO Isaiah Taylor say the company will pursue power ascension next and are targeting power operations before July 4, but that step depends on weeks of integrated tests and successful cooling, controls, shielding, and power‑conversion performance.
  • Ward 250 is a helium‑cooled high‑temperature gas reactor using TRISO particle fuel and was moved to the San Rafael Energy Lab via a February C‑17 military airlift as part of a rapid, hardware‑first development path.
  • Key constraints remain for wider deployment: reliable TRISO/HALEU fuel supplies, completion of NRC commercial licensing, and proven sustained electricity generation that meets regulatory and safety requirements.