Concrete pouring begins in the first of Hermes' 51 foundational piers
The company began groundwork last July, completing excavation in October. The Hermes project, overseen by the U.S. Nuclear Regulatory Commission (NRC), demonstrates Kairos’s KP-FHR fluoride salt-cooled high-temperature reactor technology. The concrete pour follows months of preparation, including a full-scale test pier completed in November and the drilling of 70 piers for the adjacent ETU 3.0 non-nuclear test unit, led by Barnard Construction Company, Inc. These efforts refined Kairos’s nuclear quality assurance processes.
Mike Laufer, Kairos Power’s CEO and co-founder, stated: “This achievement reflects the value of our iterative development process to meet the necessary nuclear quality standards and provide crucial real cost information that gives confidence to our customers. It is a testament to the hard work of our dedicated team and represents an enormous amount of learning and progress.”
The Hermes reactor will use tri-structural isotropic (TRISO) uranium fuel and Flibe, a mixture of lithium fluoride and beryllium fluoride salts, as its coolant. Kairos noted that this design enhances safety and simplifies the reactor structure. While Hermes will not generate electricity, it is the first non-light-water reactor permitted in the U.S. in over 50 years, supported by the U.S. Department of Energy’s Advanced Reactor Demonstration Program.
Kairos is also advancing Hermes 2, a two-unit 35 MWt plant with a power generation system, which received an NRC construction permit in November. Additionally, a master plant development agreement with Google, signed in October 2024, supports the commercial deployment of up to 500 MW of capacity by 2035.
The iterative approach, including the ETU 3.0 test unit, has allowed Kairos to optimize construction techniques and quality control, ensuring compliance with nuclear standards. The Hermes project represents a significant step in developing advanced reactor technology, contributing to clean energy innovation in the U.S.
