Research & Development

Advanced Reactor Developer Kairos Installs RPV At Nuclear Test Unit

By David Dalton
23 July 2025

Company aims to deploy Generation IV KP-FHR technology

Advanced Reactor Developer Kairos Installs RPV At Nuclear Test Unit
The RPV is the central component in Kairos’ non-nuclear ETU 3.0 reactor mockup. Courtesy Kairos Power.

US advanced nuclear reactor developer Kairos Power has successfully installed the reactor pressure vessel (RPV) for its third Engineering Test Unit (ETU 3.0) at the company’s campus in Oak Ridge, Tennessee.

The four-metre vessel is the central component in Kairos’ non-nuclear ETU 3.0 reactor mockup and its installation marks a significant milestone for the company in the construction of the facility.

Kairos is using its ETU programme to validate a safe, cost-effective pathway for the future deployment of its Generation IV fluoride salt-cooled high-temperature reactor (KP-FHR) technology in the US.

The ETU 3.0 facility will serve as a vital proving ground to refine civil construction methods and quality assurance procedures for Kairos’s Hermes Low-Power Demonstration Reactor, and will ultimately support the Hermes reactor as an operator training centre and test platform for remote handling and maintenance equipment.

The RPV for the ETU 3.0 was fabricated in partnership with the UK’s University of Sheffield and Cambridge, England-based mechanical engineering company Cambridge Vacuum Engineering.

In May, Kairos completed the first installation of nuclear safety-related concrete for the Hermes Low-Power Demonstration Reactor, marking the start of “nuclear construction” on the project.

Hermes is a scaled demonstration of the KP-FHR technology and the first advanced nuclear reactor to receive a construction permit from the US Nuclear Regulatory Commission.

In October tech company Google announced it would back the construction of seven SMRs from Kairos Power, becoming the first tech company to commission new nuclear power plants to provide low-carbon electricity for its energy-hungry data centres.

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