Westinghouse eVinci Microreactor Completes Zero-Power Criticality Testing

Westinghouse Electric Company announced on August 25 that its eVinci microreactor has completed zero-power criticality testing, validating relevant models and key assumptions in the core design. The test was completed at 10:39 a.m. Pacific Time on August 24, 2026, at the National Criticality Experiments Research Center (NCERC) at the Nevada National Security Site (NNSS). The center is operated under the U.S. National Nuclear Security Administration (NNSA).

The test was conducted by Westinghouse Electric in collaboration with Los Alamos National Laboratory (LANL) and Idaho National Laboratory (INL). Zero-power criticality is typically used to verify that a reactor core can achieve a self-sustaining chain fission state at extremely low power levels, serving as a critical step in reactor physics testing and design validation.

Westinghouse Electric stated that this milestone is part of its rapid product development program, which accelerates technology maturation and reduces engineering risk through testing, modeling, simulation, and design iteration. Subsequent prototype testing and demonstrations will continue to validate the performance, operability, and manufacturability of the eVinci technology, providing a basis for further design optimization.

Lou Martinez Sancho, Chief Technology Officer of Westinghouse Electric, stated that this zero-power criticality test represents a significant milestone in the company's advancement of nuclear energy innovation, and expressed gratitude to the U.S. Department of Energy (DOE), NNSA, LANL, INL, and other organizations for their support and collaboration during the test.

According to Westinghouse Electric, the eVinci microreactor features advanced heat pipe technology, TRISO fuel, graphite core materials, control drum assemblies, and a compact structural design, with target applications including remote areas, harsh environments, defense missions, and space energy supply. The design is intended to provide continuous, stable electricity for up to eight years without refueling.