The Nuclear Regulatory Commission (NRC) has achieved a significant milestone by voting to grant construction permits for Kairos Power's Hermes 2 project. The facility, which comprises two 35-MWth molten salt reactors with a combined thermal capacity of 70 MWth, is set to become the first electricity-producing Generation IV reactor approved for construction in the United States. “Following the Commission’s vote, Hermes 2 is now the first electricity-producing Gen IV plant to be approved for construction in the United States,” stated Kairos Power.

The Hermes 2 facility will be constructed at the East Tennessee Technology Park Heritage Center in Oak Ridge, Tennessee. This site is also planned to host the single-unit, 35-MWth Hermes 1 reactor, a non-nuclear engineering test unit, along with a potential Kairos Power fuel fabrication facility.

Hermes 1, a non-power demonstration reactor, began construction in July 2024 and is expected to be completed by 2027. If Hermes 2 construction proceeds as planned, its two reactors, capable of generating 20 MWe, could begin operation by December 2027.

The NRC’s permit approval for Hermes 2 is a crucial step in the two-phase CFR Part 50 licensing process. An operating license will still be required before the reactors can become operational. Once operational, Hermes 2 is expected to have a licensed lifetime of 11 years.

According to Kairos Power, the Hermes series is a key part of its efforts to commercialize its fluoride salt-cooled, high-temperature reactor (KP-FHR) technology. The 70-MWth Hermes 2 plant is designed to “demonstrate complete plant architecture at a reduced scale and supply clean electricity to the grid, further advancing technology, licensing, supply chain, and construction certainty for Kairos Power’s commercial deployments.”

Kairos’ Iterative Approach to Innovation

Since its founding in 2016, Alameda, California-based Kairos Power has utilized a “rapid iterative development approach” to develop its KP-FHR technology. This strategy emphasizes hardware demonstrations and in-house manufacturing to drive cost reductions and achieve regulatory approvals.

The KP-FHR system incorporates a graphite-moderated pebble-bed reactor with molten fluoride salt coolant operating at high temperatures and near-atmospheric pressure. Fuel for the system consists of TRISO (tri-structural isotropic) particle fuel in pebble form, designed with a carbonaceous-matrix coating for enhanced safety.

Future offerings from Kairos Power include the KP-X Commercial Demo Plant, a 50-MWe single-unit reactor, and the KP-FHR Commercial Plant, a dual-unit 150-MWe configuration. These reactors will use high-assay low-enriched uranium (HALEU) enriched to 19.74%.

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Kairos has already begun collaborating with tech giant Google under a Master Plant Development Agreement to develop a 500-MW fleet of molten salt reactors by 2035. The first unit is expected to be operational by 2030, aligning with Google’s goal of achieving 24/7 carbon-free energy.

Progress Through Regulatory Milestones

Kairos Power has achieved multiple regulatory breakthroughs with the NRC. Notably, the approval of Hermes 1 in December 2023 marked the first green light for a non-water-cooled reactor in over 50 years.

The NRC’s expedited review process for Hermes 2, completed in just 16 months, showcases new efficiencies in licensing innovative reactor designs. “While keeping safety at the forefront, the permitting process was quite efficient, and we issued these permits in less than 18 months,” remarked NRC Chair Christopher Hanson.

Kairos attributes this efficiency to its extensive pre-application engagement with the NRC, dating back to 2018, and the co-location of the Hermes 1 and Hermes 2 projects, which streamlined the review process. Peter Hastings, vice president of Regulatory Affairs & Quality, emphasized that the licensing basis established through these permits will serve future applications, fostering continued innovation in nuclear reactor development.

Darrell Gardner, Kairos’ senior licensing director, praised the collaboration with the NRC, calling the process a “testing ground for more efficient processes that will benefit the entire industry.” He added, “Kudos to the NRC and to the entire Kairos Power team for another job well done.”