US-based Kairos Power has installed the reactor vessel for its third Engineering Test Unit (ETU 3.0), which is under construction at its Oak Ridge campus in Tennessee. ETU 3.0 will be used to inform the design of the Hermes low-power reactor also under construction at the Oak Ridge site.
Kairos Power, founded in 2016, is headquartered in Alameda California. In 2023, the US Nuclear Regulatory Commission (NRC) issued a construction permit for Kairos Power’s Hermes demonstration reactor – the first non-water-cooled reactor to be approved for construction in the US in more than 50 years.
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. Hermes will use a TRISO pebble bed fuel design.
Kairos believes the Hermes demonstration reactors will help to 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. The project is being supported through the Department of Energy’s (DOE’s) Advanced Reactor Demonstration Program (ARDP).
ETU 3.0 is a non-nuclear prototype that will be used to pilot new manufacturing techniques and construction processes to lower the cost of building the company’s commercial reactor. The ETU programme is intended to mature internal manufacturing capabilities, mitigating supply chain risk for the Hermes demonstration reactor series and Kairos Power’s commercial fleet.
In February, Kairos completed design, construction, and installation of the reactor vessel for ETU 2.0 which was intended to demonstrate KP-FHR system integration in an optimised, fully modular design, building on lessons learned from ETU 1.0.
The installation of the 14-foot-tall ETU 3.0 vessel is a significant construction milestone for the non-nuclear reactor mock-up. The reactor vessel was lowered into position using construction cranes and mounted on a support structure attached to the building’s foundation.
Kairos Power is also working with Barnard Construction to construct the ETU 3.0 building around the reactor vessel in a streamlined sequence, which allowed the oversized component to be moved into position before the roof and other elements are in place.
The ETU 3.0 reactor vessel was fabricated in partnership with Cambridge Vacuum Engineering (CVE) and the University of Sheffield’s Advanced Manufacturing Research Centre (AMRC), using electron beam welding (EBW) technology. EBW produces high-quality welds at least an order of magnitude faster than conventional arc welding. “Large demonstrations like the ETU 3.0 reactor vessel are vital for effectively bringing advanced manufacturing methods into industry, offering a holistic solution for fabricating complex, large-scale components,” said University of Sheffield AMRC interim CEO Ben Morgan.
“The collaboration with Kairos Power, CVE, and the AMRC underscores the transformative potential of electron beam welding in advanced manufacturing,” said CVE Managing Director Bob Nicolson. “The technology scales well to the precise and demanding requirements of nuclear construction, and this partnership represents a significant step forward in SMR commercialisation.”
“The installation of our third ETU reactor vessel marks a significant moment on our commercial development pathway,” said Kairos Power Chief Technology Officer and co-founder Edward Blandford. “ETU 3.0 will serve an important mission as a testing and training platform to ensure safe and efficient operation of the Hermes reactor. But, more broadly, the expertise and capabilities we gain from the ETU programme will help pave the way to successfully deploy Kairos Power’s commercial fleet.”
ETU 3.0 will serve as an operator training centre and test platform for Hermes remote handling and maintenance equipment. The facility will also support the staging, assembly, and testing of Hermes plant equipment modules prior to installation. The modular reactor construction methods being piloted with the ETU series and Hermes will help to reduce construction costs and timelines for future plant deployments.
The ETU 3.0 vessel installation is a contract milestone under Kairos Power’s Technology Investment Agreement with DOE for up to $303m in risk reduction funding through ARDP. Under the agreement, Kairos Power receives fixed, performance-based payments from DOE upon demonstrating the completion of pre-determined project milestones.
“Kairos Power’s novel contract with DOE allows us to remain agile while demonstrating continued progress as a responsible steward of public funding,” said Kairos Power CEO and co-founder Mike Laufer. “ARDP support is helping us to move quickly through progressively sophisticated iterations, gaining essential learning that will enable commercial deployment of our advanced reactor technology on a meaningful timeline.”
