US-based Kairos Power has signed a technology investment agreement with the Department of Energy (DOE) to put into effect the Advanced Reactor Demonstration Program (ADRP) risk reduction award, which the company received in 2020. Under the agreement, DOE will provide up to $303m on a performance-based, fixed-price milestone basis to enable the design, construction, and commissioning of the company’s Hermes demonstration reactor. A construction permit for the reactor was issued by the. Nuclear Regulatory Commission (NRC) in December 2023.

The Hermes design is for a 35 MWt non-power version of the company's fluoride salt-cooled high temperature reactor, the KP-HFR. Kairos has also submitted a construction permit application for Hermes 2, a proposed two-unit demonstration plant that would build on the experience of Hermes and would produce electricity and demonstrate the complete architecture of future commercial plants. The Hermes demonstration reactors will help mitigate technology, licensing, supply chain, and construction risk to achieve cost certainty for KP-HFR technology. Kairos is targeting commercial deployments in the early 2030s. Hermes is to be built at Oak Ridge, Tennessee.

Kairos Power is conducting salt operations at its first engineering test unit (ETU) in New Mexico. The ETU is a non-nuclear, full-scale mock-up of Hermes that will demonstrate key systems and components of the reactor, test the supply chain, and allow workers to gain operational experience. Kairos will build and operate a total of three ETU iterations before constructing Hermes.

Mike Laufer, Kairos Power co-founder and CEO, noted: “With the use of fixed-price milestone payments, this innovative contract provides real benefits to both Kairos Power and DOE to ensure the successful completion of the Hermes reactor. It allows us to remain focused on achieving the most important goals of the project while retaining agility and flexibility to move quickly as we learn key lessons through our iterative development approach.”

DOE Office of Nuclear Energy Assistant Secretary Dr Kathryn Huff said the Hermes reactor “is an important step toward realising advanced nuclear energy’s role in ushering forward the nation’s clean energy transition”. She added: “Partnerships like this one play a significant role in making advanced nuclear technology commercially competitive.”

The KP-HFR is one of five teams selected in 2020 by the DOE to receive $30m in initial funding for risk reduction projects under the ARDP. The other projects were Westinghouse Electric Company’s eVinci Microreactor, the BWXT Advanced Nuclear Reactor (BANR), Holtec’s SMR-160 Reactor, and Southern Company’s Molten Chloride Reactor Experiment. DOE had earlier in 2020 selected TerraPower and X-energy to receive $160m in initial funding for ARDP Demonstration projects to develop two advanced nuclear reactors to be operational within seven years.

Image: Rendering of the Hermes demonstration reactor plant (courtesy Kairos Power)