Valar Atomics Ward 250 reactor achieves criticality, beats DOE by 3 months
In brief
- Ward 250 microreactor achieved criticality on March 31, 2026, sustaining a self-sustaining nuclear chain reaction
- Milestone arrived three months ahead of DOE's Nuclear Reactor Pilot Program target of July 4, 2026
- Valar raised $450 million at $2 billion valuation in March 2026 to fund helium-cooled microreactor deployment
- Company targets power operations within ten months of groundbreaking, versus decades for traditional nuclear projects
From stealth to criticality in 14 months
Valar Atomics emerged from stealth in early 2025 under CEO Isaiah Taylor with an ambitious mandate: compress nuclear development timelines from decades into months. The company raised a $19 million seed round in February 2025, then completed a non-nuclear prototype called Ward Zero in February 2025. By November 2025, funding had grown to a $130 million round. Then in March 2026, Valar closed a $450 million raise at a $2 billion valuation.
The company broke ground on the Ward 250 project on September 17, 2025. Before that, Valar had validated its core physics models through a cold criticality test of a subscale NOVA Core model at Los Alamos National Laboratory on November 17, 2025. In February 2026, the company airlifted Ward 250 reactor components to Utah using a C-17 military transport aircraft.
Criticality itself marks a threshold moment. The reactor can now sustain a nuclear chain reaction on its own, which is the foundational step before a reactor can actually generate power. Think of it as the nuclear equivalent of an engine turning over for the first time.
Why this matters for nuclear's future
The Ward 250 is a helium-cooled high-temperature gas reactor that uses TRISO fuel. TRISO fuel consists of uranium particles coated in multiple layers of ceramic and carbon, a design that tolerates extreme temperatures and reduces meltdown risk. Valar has partnered with Kiewit and the San Rafael Energy Lab to accelerate deployment.
For context, traditional nuclear projects measure timelines in decades, not months. The much-discussed Vogtle Units 3 and 4 in Georgia took roughly 14 years from initial license application to commercial operation. Valar is now targeting power operations within ten months of groundbreaking—a compression that, if sustained, could reshape how energy infrastructure scales globally.
The whole point of a microreactor is that you can move it. Traditional nuclear plants are massive, site-specific infrastructure projects. Valar is building something closer to a product than a construction project.
