California Startup Claims Historic ‘First’ in Fission Reactor Milestone

In May, a series of executive orders from the Trump administration signaled a sweeping shift to nuclear energy in the United States. Despite some obstacles along the way – namely major upheaval in nuclear regulation – the nuclear industry is progressing at a “pace not seen since the Manhattan Project”, according to industry observers. Now, one of nuclear power’s newest players claims to have taken a small but important first step toward making those ambitions a reality.

California-based startup Valar Atomics announced that it has achieved zero-power criticality on November 17 at 2:45 pm ET. Criticality refers to a stage for a nuclear reactor in which each fission event – ​​the splitting of a heavyweight atom – releases enough neutrons to sustain chain reactions. The result was a collaboration between Valar Atomics and Los Alamos National Laboratory (LANL), which provided the operational capability and other key technologies for the experiment.

Valar claims it is the first nuclear startup to reach criticality, as well as the first to do so among startups participating in the Department of Energy’s pilot program to bring at least three startups to criticality by July 4, 2026.

“Zero power criticality is the first heartbeat of a reactor, a proof of physics,” Isaiah Taylor, CEO and founder of Velar, said in the statement. “This moment marks the beginning of a new era in American nuclear engineering – one defined by speed, scale, and private sector execution coupled with close federal partnership.”

some warnings

To be clear, reaching criticality does not mean the reactor is ready to generate electricity. Velar has achieved what is called cold criticality or zero-power criticality, which helps validate the reactor design but does not actually produce heat to make power.

This feat is still impressive, considering that the company only launched earlier this year. As if to compensate for its late entry into the industry, Valar has set aggressive goals in its effort to move forward, including delivery of a fully operational reactor by the July deadline set by executive order in May.

So far, they seem to be on track. Just last week, Velar reported securing $130 million in funding. In September, they began work at their first physical location for a reactor in Utah.

The latest criticality experiments tested the firm’s Nova Core, which is based on LANL’s previous structural designs. The company reported that the experiments were conducted by LANL itself and closely modeled the real-life conditions planned for Weller’s upcoming reactor.

A nuclear renaissance?

These developments reflect major industry shifts following the Trump administration’s almost hawkish approach to nuclear regulation. Prior to this series of executive orders, startups had received stringent regulatory oversight from the Nuclear Regulatory Commission (NRC), which the companies claimed stifled innovation.

Valar, along with Last Energy and Deep Fission, actually filed a lawsuit against the NRC late last year, criticizing the agency for “blocking” small-scale nuclear innovation. The lawsuit has not yet been resolved, although Weller has consistently praised the current administration’s approach to nuclear reform, calling it “the most comprehensive nuclear policy reform in decades” and “America’s nuclear renaissance.”

Adam Stein, director of the Nuclear Energy Innovation Program at the Breakthrough Institute, told Wired that the executive order changes the mindset behind interpreting the legal framework for nuclear energy tests. “It basically emphasizes that if [a reactor] “Not yet commercially deployed, so it is inherently a research system,” he said.

In fact, improvements have allowed accelerated progress, such as the critical testing of the Velar. At the same time, others have expressed concerns about lax safety regulations based on decades of research and experiments. For better or worse, it remains to be seen whether the changes will prove to be a long-term positive for the US nuclear industry.

Meanwhile, Velar plans to continue criticality testing for its NOVA core at LANL facilities.