Kairos Power began construction on its Hermes non-powered demonstration reactor in Oak Ridge, Tennessee in July 2024, targeting activation in mid-2026. Hermes is a 35 MWe fluoride salt-cooled high-temperature reactor — the non-nuclear portion of which has been completed. The NRC approved Kairos's Hermes construction permit in December 2023, and the NRC also approved plans for Hermes 2. Hermes uses TRISO pebble fuel in a molten lithium-fluoride beryllium-fluoride salt coolant, operating at atmospheric pressure. The first activation is one of the most anticipated milestones in US advanced nuclear in 2026. Kairos installed the reactor pressure vessel for a third test unit in 2025 and unveiled a training simulator laboratory at the University of Tennessee. In October 2024, Google signed an agreement to commission multiple Kairos SMRs, with the first operational by 2030. In September 2026, Samsung C&T agreed to make a $70 million equity investment in Kairos alongside in-kind engineering services, together worth up to $100 million, to help build Hermes 2 — Kairos's first commercial-scale reactor, whose output will count as the first 50 MW toward its Google deal, which calls for approximately 500 MW of capacity by 2035. Samsung C&T has built or helped build roughly a dozen nuclear reactors globally.