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Valar Atomics Reaches Cold Criticality in Los Alamos–Backed Test

The zero-power milestone under a DOE pilot verifies the reactor’s physics without generating electricity.

Overview

  • The company reported achieving a sustained chain reaction on November 17 at the Nevada National Security Site using its fuel with Los Alamos structural components.
  • The test is part of the DOE Reactor Pilot Program that treats early systems as research reactors and accelerates criticality goals set for July 4, 2026.
  • Valar says it is the first venture-backed startup to sustain a controlled fission reaction, framing the result as the start of broader reactor trials.
  • Days earlier, Valar closed a $130 million funding round led by Palmer Luckey and Palantir CTO Shyam Sankar to speed development.
  • The cold-critical check is a prudent step given limited prior fuel testing, and commercial operation will still require further testing and NRC approval as the firm contests aspects of NRC oversight in court.