US-based Kairos Power has completed a second Flibe production run at its Molten Salt Purification Plant (MSPP) at the Materion campus in Elmore, Ohio. MSPP was completed and commissioned in 2022 through a partnership between Kairos Power and Materion, designed to produce high-purity Flibe (fluoride-lithium-beryllium) molten salt for its molten salt-cooled high-temperature reactors (KP-FHR).
The reactors, Hermes 1 and Hermes 2, are co-located advanced nuclear demonstration reactors being built at the Oak Ridge campus. They use KP-FHR technology, combining TRIsructural ISOtropic (TRISO) fuel pebbles with a molten Flibe salt coolant to achieve robust inherent safety at low pressure.
Hermes 1 is thermal only (35 MWt) producing no electricity, is intended to prove that the KP-FHR nuclear system functions reliably under real nuclear operations. Expected completion date is 2028–2029. Hermes 2 consists of two 35 MWt reactor units that together will supply 50 MWe of electricity to the Tennessee Valley Authority (TVA) grid. Operation is targeted for 2030.
These are supported by a series of engineering test units (ETUs) designed to solve different engineering challenges. ETU 1, built at Kairos Power’s manufacturing development campus in Albuquerque (New Mexico), focused on fluid dynamics and chemistry. It completed more than 2,000 hours of pumped Flibe molten salt operations before being decommissioned.
ETU 2, also built in Albuquerque, focused on modular manufacturing to validate the vertical integration strategy by building over 30 separate equipment modules and testing full in-house reactor vessel fabrication. ETU 2 will directly inform the construction, commissioning, and operation of Hermes. The data generated will help confirm how the molten salt, pebble bed, and graphite internals interact within the vessel.
MSPP previously produced approximately 14 tonnes of high-purity Flibe for ETU 1 testing. This first production campaign combined lithium fluoride and beryllium fluoride to demonstrate Flibe production and processing on an industrial scale. For ETU 2, the MSPP process has been upgraded to produce salt using more advanced processing and purification techniques to reach the purity levels required for nuclear coolant applications.
The improvements produced high-purity, better-characterised Flibe that will provide valuable baseline data on its composition ahead of the ETU 2 hardware demonstration. It will also help improve the process that is being designed for the Salt Production Facility (SPF), now under construction at the Albuquerque campus. SPF will produce high-purity, lithium-7-enriched Flibe for Kairos Power’s nuclear reactors, building on the processes demonstrated in MSPP.
Flibe previously used in ETU 1 will be repurposed for ETU 2. “The working conditions inside MSPP require us to make every minute count,” said Paige Pierce, an engineer on the Salt team. “By improving our remote capabilities, planning tools, communications, and safety monitoring, we made the campaign safer and more efficient, while providing valuable lessons for designing and operating future salt production systems.”
Kairos will ship the newly produced Flibe to the Manufacturing Development Campus in Albuquerque to prepare for ETU 2 operations early next year. There, the team will combine it with Flibe previously used in ETU 1 to deliver approximately 16 tonnes of salt for the demonstration.
With each production campaign, the Kairos team applies lessons learned to improve manufacturing processes, refine molten salt chemistry, and reduce technical risk on the path to commercial deployment.
