Hermes

Overview

35 MWth low-power demonstration reactor validating Kairos Power's KP-FHR design, construction methods, fuel program, and operating approach in Oak Ridge, Tennessee.

Construction permit granted in December 2023 and nuclear safety-related construction began in May 2025. In May 2026 the NRC extended the construction-completion deadline by 28 months to April 30, 2029 after first-of-a-kind site and design delays; Kairos now expects to finish building the reactor in 2028, pushing operation past the original 2027 target. As of late August 2026 no further NRC schedule action has been taken and no operating license application has yet been filed for Hermes 1.

Key Specs