Westinghouse tests eVinci reactor at zero power

Inside the National Criticality Experiments Research Center in Nevada, engineers put Westinghouse’s eVinci microreactor core through a test that produced no electricity. Completed on August 24, the zero-power criticality experiment examined the core’s nuclear behavior without operating the reactor at full power.

The point was comparison. Westinghouse, Los Alamos National Laboratory and Idaho National Laboratory collected experimental data to test the models and assumptions behind the design. The company says this cycle of physical testing, computer modeling, simulation and design changes is meant to expose technical issues earlier, before the reactor moves through more prototypes and demonstrations.

The eVinci architecture is built around heat pipes, which transfer energy from the core without the large pumping systems used in some conventional reactor designs. Its compact format also combines TRISO fuel, graphite core materials and control drums. Westinghouse says the system could supply electricity continuously for up to eight years without refueling.

That could matter in places where the usual answer—building grid connections or moving fuel—is difficult: isolated communities, industrial sites, defense operations and space missions are among the company’s targets. The test does not establish that the reactor is ready for those users; it gives engineers a measured checkpoint before assessing performance, operation and manufacturability in later work.

Concretely, the near-term benefit is better evidence for the next design decisions, not power on the grid. Westinghouse has not announced a commercial operating date, and the reactor remains at a laboratory validation stage, with prototype testing and demonstrations still ahead.