Westinghouse Electric Company reached a key milestone earlier this month when it successfully completed criticality testing for its eVinci microreactor. The work was completed by Los Alamos National Laboratory in collaboration 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. The eVinci microreactor criticality testing was conducted at the National Critical Experiments Research Center (NCERC), a National Nuclear Security Administration facility located in Nevada. Testing eVinci at core temperatures upward of 1,000 degrees Celsius yielded invaluable data about the reactor’s performance as Westinghouse works to move this advanced nuclear design toward commercialisation. The eVinci test brings the system one step closer to real-world conditions On September 3, 2026, the eVinci test reached criticality at 663 degrees Celsius. Westinghouse researchers measured a peak core temperature of 1,011 degrees Celsius, a record-high temperature for a reactivity measurement at NCERC. The tests generated high-quality temperature data that Westinghouse will use to strengthen its analytical models and accelerate the eVinci reactor prototype design. This continues …

The U.S. Department of Energy (DOE) has announced that Aalo Atomics has successfully achieved advanced reactor criticality with its Aalo-X test reactor at Idaho National Laboratory, marking another milestone for the country’s next-generation nuclear energy programme. The zero-power-fuelled criticality demonstration was completed under the DOE’s Reactor Pilot Program, making Aalo-X the fourth DOE-authorised advanced reactor design to reach criticality. The achievement also exceeds the federal target established in President Donald Trump’s May 2025 executive order, which called for three advanced reactors to achieve criticality by the July 4 deadline. The result highlights the accelerating pace of advanced nuclear development in the United States, reinforcing the Reactor Pilot Program as a key pathway for demonstrating new reactor technologies while supporting broader efforts to expand domestic nuclear energy capacity. Aalo-X strengthens momentum for advanced reactor criticality The successful test adds Aalo-X to a growing list of advanced reactor projects that have recently reached the same milestone through the DOE programme. During June, Antares Nuclear’s Mark-0 reactor, Valar Atomics’ Ward 250 reactor and Deployable Energy’s Unity reactor each …