DOE approves Radiant's Kaleidos safety analysis for full-power testing

Radiant says the Department of Energy has approved the documented safety analysis for its Kaleidos microreactor, and that the approval covers operation at power as well as initial criticality. The company announced the approval on October 29, 2026. Next comes a DOE readiness review of the reactor and the team that will operate it; once that is complete, Radiant will fuel Kaleidos inside the DOME test bed at Idaho National Laboratory.

The campaign behind that review is the real test. Radiant plans five phases climbing from first criticality through increasingly higher power, ending in at least 150 hours of continuous full-power operation without operator intervention, and says it will run the same unit for 60 effective full-power days over several months. The approval follows DOE's February 2026 approval of Radiant's preliminary safety analysis.

Radiant calls Kaleidos the only microreactor design with DOE safety-analysis approval for full-power operations. "This approval for full power demonstration is a first within the microreactor industry," said Rita Baranwal, Radiant's chief nuclear officer. At the same laboratory, by comparison, the final safety analysis DOE approved for INL's own MARVEL test reactor authorizes a dry criticality run at near-zero power.

The calendar has moved. When Kaleidos left El Segundo, California in August, Radiant targeted the 150-hour run for the third quarter of 2026. The third quarter ended with the reactor still unfueled, and the new release gives no date for the readiness review or for criticality.

The test is the gate to the product. Radiant plans to manufacture Kaleidos at its R-50 facility in Oak Ridge, Tennessee, and deliver its first commercial units to Buckley Space Force Base and Fort Benning in 2028. The Navy picked Kaleidos for a prototype at Naval Weapons Station Crane on October 20, and HALEU for multiple Kaleidos units is on contract with Centrus, with deliveries scheduled to begin before the end of the decade.