Westinghouse eVinci microreactor reaches criticality at 663 C
Peak core temperature reached 1,011 C, a record for a reactivity measurement at the National Critical Experiments Research Center, the DOE Office of Nuclear Energy said.
Key facts
- Criticality reached September 3, 2026 at NCERC, an NNSA facility
- Los Alamos National Laboratory ran the work with Idaho National Laboratory and the Nevada National Security Site
- eVinci is a transportable, heat-pipe-cooled design using TRISO fuel, rated at 5 MW of electricity
- Commercial version expected to run eight or more years before refueling, per Westinghouse
- Selected in August 2026 for the next phase of the U.S. Army's Janus Program
Westinghouse Electric Company completed criticality testing of its eVinci microreactor, the DOE Office of Nuclear Energy said on September 16. The test reached criticality on September 3 at 663 degrees Celsius. Researchers measured a peak core temperature of 1,011 degrees Celsius, which the office said is a record-high temperature for a reactivity measurement at the National Critical Experiments Research Center.
The work was carried out by Los Alamos National Laboratory with Idaho National Laboratory, the Nevada National Security Site and the DOE/NRC Collaboration for Criticality Safety Support for Commercial-Scale HALEU Fuel Cycles and Transportation. NCERC is a National Nuclear Security Administration facility in Nevada.
Westinghouse will use the temperature data to strengthen its analytical models and accelerate the eVinci prototype design, the office said. The testing follows zero-power criticality testing of the design.
eVinci is a transportable, heat-pipe-cooled reactor that runs on TRISO fuel and is designed to produce 5 megawatts of electricity on sites as small as two acres. It is one of several designs that received funding from DOE's Advanced Reactor Demonstration Program. Westinghouse expects the commercial version to operate for eight or more years before refueling.
In August 2026, eVinci was selected for the next phase of the Janus Program, the U.S. Department of the Army's initiative to power U.S. military installations with microreactors.