goingcritical:valar-ward-250United States · Microreactor

Valar Atomics Ward 250

Developer: Valar Atomics

Site: San Rafael Energy Research Center, Emery County, Utah

Status: Critical since June 18, 2026 critical

Summary:

First DOE-authorized reactor built outside a national laboratory; DOE-authorized zero-power fueled criticality June 18 (company reported an earlier non-DOE zero-power criticality in Nov 2025); power ascension to 10 kWt on June 22, 2026

Details

DesignHelium-cooled, graphite-moderated, HALEU TRISO-fueled high-temperature gas reactor (100 kWt)
CapacityUndisclosed

Milestone history

  1. Announced August 12, 2025
  2. Construction start September 25, 2025
  3. Fuel load —
  4. First criticality June 18, 2026

References

  1. DOE, second advanced reactor criticality under Reactor Pilot Program
  2. ANS Nuclear Newswire, Valar's Ward 250 reaches criticality in Utah (June 18, 2026)
  3. ANS Nuclear Newswire, Reactor Pilot Program deadline check-in (July 2, 2026 — groundbreaking Sept 25, 2025; 10 kWt ascension)
  4. Partnership for Global Security, RPP status (notes Nov 2025 zero-power criticality claim)
  5. DOE, initial Reactor Pilot Program selections (Aug 12, 2025)