US Kairos Completes First Phase Testing of ETU 3 Reactor Model

Kairos Power announced on September 7 that its Engineering Test Unit 3 (ETU 3) has completed the first phase of testing. The testing, centered on the Hermes 2 reactor cavity model, validated the precast concrete shielding design as well as remote operation and maintenance capabilities, providing support for the design of the Hermes 2 demonstration plant and subsequent commercial units.

Reactor cavity model (Image: Kairos Power)

ETU 3, located in Oak Ridge, Tennessee, is part of Kairos Power's fluoride salt-cooled high-temperature reactor (KP-FHR) technology iterative development program. The unit is a scaled, non-nuclear mockup cavity consisting of a reactor pressure vessel and precast concrete shielding structures. The shielding structures are manufactured using 3D-printed polymer composite materials and supported by steel frames, with the related processes developed in collaboration with the Manufacturing Demonstration Facility at Oak Ridge National Laboratory (ORNL).

In this demonstration round, each panel of the shielding structure was equipped with steel frame openings to test different types of concrete shield plug designs. These shield plugs allow reactor process lines to pass through the shielding structure and connect to other areas of the plant. The connection and disconnection of these lines are planned to be carried out through a remote handling system to reduce interruptions during operation and maintenance.

In April of this year, Kairos Power held a groundbreaking ceremony for Hermes 2 at the former Oak Ridge Gaseous Diffusion Plant site. The company's Hermes 1 low-power demonstration reactor, also under construction in Oak Ridge, is likewise a scaled demonstration reactor. Hermes 1 is the first non-light-water reactor approved for construction by the U.S. Nuclear Regulatory Commission (NRC). It does not generate electricity itself, and the experience gained during its construction and operation will be applied to the Hermes 2 project.

Ed Blandford, co-founder and chief technology officer of Kairos Power, stated that the initial demonstration completed by ETU 3 is an important step toward establishing a sustainable maintenance philosophy for future units. By validating the interfaces between the modular shielding structures and reactor equipment, and testing the remote handling tools required for maintenance and component replacement, the company can further clarify the design features that need to be standardized for future KP-FHR commercial deployment.

ETU 3 is the third engineering test unit in the program and will be used to refine subsequent design options for the Hermes 2 reactor cavity and provide a training platform for future operators. Previously, ETU 1.0, as a full-scale electrically heated prototype of the Hermes reactor, completed more than 2,000 hours of salt pumping operation, validating key system design and integration as well as supply chain capabilities, including the production capacity for high-purity fluoride lithium-beryllium salt (FLiBe) coolant. ETU 2.0, subsequently constructed, is a non-power unit primarily used to demonstrate modular construction methods.