The U.S. Department of Energy (DOE) has taken a significant step toward advancing microreactor technology, announcing the selection of Westinghouse and Radiant Industries to conduct the first fueled experiments at the Demonstration of Microreactor Experiments (DOME) facility, set to open at Idaho National Laboratory (INL) in early 2026. This move underscores the DOE’s commitment to fast-tracking the deployment of American microreactor technologies, which are increasingly seen as a solution to the growing demand for more abundant, affordable, and reliable power.
Westinghouse, based in Etna, Pennsylvania, will test its eVinci microreactor, a portable design capable of producing up to 5 MWe. The commercial heat pipe–cooled microreactor is designed for a variety of applications, including powering remote communities, mining operations, and data centers. Westinghouse aims to bring the eVinci to market by 2027. Meanwhile, El Segundo, California–based Radiant Industries will test the Kaleidos Development Unit, advancing its commercial Kaleidos Battery microreactor design. Founded in 2019 by former SpaceX engineers, Radiant is developing a 1.2-MWe high-temperature gas-cooled (HTGR) design that uses TRISO fuel, helium coolant, and a graphite moderator. The Kaleidos is designed to operate for five years before refueling and could provide reliable backup power to hospitals, military installations, and more.
The DOME facility, repurposed from the iconic Experimental Breeder Reactor-II (EBR-II) structure, is being retrofitted to host microreactors of up to 20 MWth. The facility’s design allows for criticality testing while maintaining regulatory thresholds for safety and environmental oversight. The DOE’s National Reactor Innovation Center (NRIC) has made rapid progress in DOME’s construction since its kickoff in October 2023, with the facility on track to receive its first experiment in early 2026.
The selection of Westinghouse and Radiant follows a competitive application process launched in 2023. Both companies were among three initial recipients—along with Ultra Safe Nuclear Corp.—of a combined $3.9 million in October 2023 under the DOE’s front-end engineering and experiment design (FEEED) program. This funding supported preliminary design, engineering, and safety documentation work required to prepare for eventual fueled testing. In November 2024, the DOE awarded a second round of funding totaling $5 million, allowing Westinghouse and Radiant to enter the detailed engineering and experiment planning (DEEP) phase. This phase includes the development of a Preliminary Documented Safety Analysis (PDSA), a critical DOE prerequisite before reactor fabrication and installation at DOME.
The DOME facility is designed to support experimental reactors using high-assay low-enriched uranium (HALEU) and includes infrastructure tailored for a range of reactor cooling methods and operational conditions. The facility offers approximately 65 feet of floor space, a 15-foot by 17-foot hatch, and penetrations for process connections and primary cooling systems. It also features a 75-ton polar crane, integrated safety-class confinement, and a dedicated duct bank connecting to a separate developer control room. Installed environmental cooling will initially be rated at 300 kWth, with expansion capacity to 500 kWth. The facility includes 480V/400-amp electrical service, support areas for external reactor equipment, and compatibility with ISO-668 shipping containers up to 40 feet.
Alongside the DOME tests, NRIC is advancing the Laboratory for Operations and Testing in the United States (LOTUS), a state-of-the-art, non-fueled test bed designed to support experimental validation of advanced reactor systems, including those intended for space and maritime applications. The facility will be located at INL’s Materials and Fuels Complex to leverage the infrastructure of the historic Zero Power Physics Reactor building and offer a 50-foot-diameter radiological confinement cell with a recessed pit, overhead crane, and 13-by-13-foot access tunnel for equipment handling. NRIC says it will support reactor demonstrations with designed outputs of up to 500 kWth and enable real-world systems testing across a range of small modular reactor and microreactor concepts. The first LOTUS user is anticipated to be the Molten Chloride Reactor Experiment (MCRE), a collaborative project led by Southern Co., TerraPower, and INL. Final design for LOTUS was completed in 2024 and construction could begin in fiscal year 2026.
The DOE is also advancing the