HWBRIEF
eVinci is a small, factory built nuclear reactor designed to ship in a container. The "self sustaining fission" result is a physics check, not a power test; heat, NRC licensing, and deployment all come later.
Westinghouse says its eVinci microreactor, a small, factory-built nuclear reactor designed to fit in a shipping container, reached self-sustaining fission in a zero-power criticality test at the Nevada National Security Site yesterday at 10:39 local time. The test ran at the National Criticality Experiments Research Center (NCERC), a National Nuclear Security Administration facility, with Los Alamos and Idaho National Laboratories and the Department of Energy.
Zero-power criticality does not produce heat or electricity. It validates whether the fuel and core geometry can sustain a controlled chain reaction at all, before any power-generating test. Westinghouse frames the result as a step on a "rapid product development" path that mixes testing, modeling, simulation, and design iteration.
The eVinci uses heat pipes to cool a core running on TRISO fuel, the ceramic-coated particles engineered to contain fission products. It is sized for 5 megawatts electric (MWe) from a 15 MWt thermal core, designed to run eight or more full-power years before refueling, and built to ship in a container for defense, remote sites, and space.
The next rungs on the deployment ladder are a heat-and-power demonstration, NRC licensing, and a first-of-a-kind operational record; none has a public schedule. "This is a major accomplishment that validates our approach," CTO Lou Martinez Sancho said in the announcement.
eVinci sits inside a 2026 cluster of microreactor programs: Oklo, X-energy, BWXT, and Holtec all have designs in motion. Each has to clear the same physics rung before any can claim a working power plant.