Kairos claims operation of world’s largest FLiBe system

21 November 2023

Kairos Power says its Engineering Test Unit (ETU) in Albuquerque has become the largest FLiBe system in the world. Kairos commissioned the plant in partnership with Materion Corporation to produce high-purity fluoride salt coolant – known as FLiBe – a eutectic mixture of lithium fluoride and beryllium fluoride.

In October, the team at the ETU began loading 14 tonnes of molten fluoride salt coolant, initiating the largest FLiBe transfer since the US Molten Salt Reactor Experiment in 1969.

ETU is a non-nuclear prototype of Kairos Power's planned fluoride salt-cooled high-temperature reactor (KP-FHR) that aims to demonstrate the integration of principal systems, structures, and components. Lessons learned from ETU will be integrated into Hermes and future iterations on the path to commercialising KP-FHR technology. This is an advanced reactor technology that uses TRISO (TRI-structural ISOtropic) fuel in pebble form combined with a low-pressure fluoride salt coolant. The technology employs a steam cycle to convert heat from fission into electricity and to complement renewable energy sources.

In September 2021, Kairos applied to the US Nuclear Regulatory Commission (NRC) for a permit to build a 35 MWt reactor that would use molten salt to cool the reactor core. The test reactor, which will not generate electricity, is intended to provide operational data for future developments. The 35 MWt Hermes demonstration reactor design was awarded $629m in cost-shared risk reduction funding over seven years by the US Department of Energy under the Advanced Reactor Demonstration Program. A site has been selected for the demonstration reactor at the East Tennessee Technology Park in Oak Ridge, and TRISO fuel pebbles will be produced at the Los Alamos National Laboratory's Low Enriched Fuel Fabrication Facility under an agreement reached in late 2022.

Last July, Kairos applied to NRC for permission to build its Hermes 2 plant next to the Hermes reactor at Oak Ridge. Hermes 2 comprises two 35 MWt reactors, each the same size as the original test reactor, that share a power generation system. Hermes 2 is a non-power stepping stone towards deployment of the KP-FHR. The purpose of Hermes 2 is to further reduce risk on the path to commercialising the KP-FHR technology, demonstrating licensing, construction, operations, training, and decommissioning of a multi-reactor plant to help estimate the cost of the first commercial unit.

Kairo said the final batch of FLiBe for ETU was delivered to the ETU in August. The FLiBe was produced at the Kairos Molten Salt Purification Plant (MSPP) on the Materion campus in Elmore, Ohio.

“Being the first to build and operate a plant to produce FLiBe at an industrial scale has generated a wealth of lessons that will help de-risk salt production for future iterations,” Kairos noted.

“As we accelerate our experience with large-scale FLiBe operations, establishing operating protocols, training personnel, and executing maintenance procedures, we learn important lessons to optimise plant operations for Kairos Power’s future nuclear iterations.” Once all 14 tonnes of FLiBe are circulating in ETU, operators will embark on a multi-month testing programme that will continue to provide data until the system is decommissioned to make way for the next iteration – ETU 2.0.

Kairos said construction work has begun on the Modular Systems Facility, which will support ETU 2.0 subsystem development. ETU 2.0 is the first iteration to demonstrate modular construction, which provides a number of benefits. “By building each subsystem for ETU 2.0 as a modular skid, we will be able to complete entire subsystems and perform qualification testing in parallel before moving the skids into the ETU enclosure for assembly. This will enable us to advance ETU 2.0 construction while ETU 1.0 operations and decommissioning are still in progress.”

Kairos is also producing “components from stainless steel and graphite, U-stamped pressure vessels, non-nuclear TRISO pebbles, and other specialised parts for our testing programme”. This includes construction of a vessel shop where we will make reactor vessels for future iterations, “along with the TRISO Development Lab, where we will advance fuel manufacturing techniques that will be implemented off-site to produce the fuel for Hermes”.

The infrastructure and experience that Kairos Power is building in Albuquerque will directly support deployments in Tennessee, including the Hermes demonstration reactor, the company noted. “But Hermes won’t be our first hardware demonstration in Oak Ridge. In August, we announced that the third ETU iteration – ETU 3.0 – will be constructed on land owned by Kairos Power adjacent to the Hermes site at Heritage Centre Industrial Park.” Kairos Power plans to break ground at Heritage Centre in early 2024.

Image: Kairos Power's Engineering Test Unit in Albuquerque (courtesy of Kairos Power)

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