Westinghouse has completed a zero power criticality test of its eVinci microreactor design at the National Criticality Experiments Research Center in Nevada, a step the company says validates the models and core design assumptions behind the technology. The test was conducted in partnership with Los Alamos National Laboratory and Idaho National Laboratory, and Westinghouse plans to continue prototyping the system to further confirm its performance, operability and manufacturability.
The eVinci test unit is a one fifth scale representation of the commercial design, which is being developed as a 5 megawatt electric microreactor with a refueling cycle of eight years or longer. The design uses heat pipes for passive heat transport, a closed Brayton cycle power conversion system, TRISO fuel, and control drums for reactivity control. Westinghouse has positioned eVinci for remote and off grid applications, including research, defense installations and lunar surface power.
The criticality test builds on several other eVinci milestones. In 2022, NASA selected Westinghouse to provide an initial design concept for a smaller, 40 kilowatt version of the reactor for potential lunar use. Pennsylvania State University has submitted a letter of intent to the NRC to host and operate an eVinci unit as a campus research reactor, and in April the US Air Force selected Westinghouse as a potential developer and operator of microreactors at Air Force installations under its Advanced Nuclear Power for Installations program.
The testing took place through the Demonstration of Microreactor Experiments program run by Idaho National Laboratory's National Reactor Innovation Center, which awarded Westinghouse early funding in 2023 to design an evaluation program for the eVinci test reactor.
Source: American Nuclear Society, Nuclear Newswire - https://www.ans.org/news/2026-08-26/article-8341/evinci-completes-cold-criticality-test-at-ncerc/