Kairos begins operation of molten salt system

12 January 2024

US-based Kairos Power has completed 1,000 hours of pumped salt operations after loading 12 tonnes of FLiBe molten fluoride into its Engineering Test Unit (ETU) at its testing and manufacturing facility in Albuquerque, New Mexico. FLiBe comprises a mixture of lithium fluoride (LiF) and beryllium fluoride (BeF2). It is both a nuclear reactor coolant and solvent for fertile or fissile material. It served both purposes in the Molten-Salt Reactor Experiment (MSRE) at the Oak Ridge National Laboratory in 1969.

The ETU and will be used to inform the design, construction, and operation of Kairos’s Hermes low-power reactor that the company is using to advance the development of its planned fluoride salt-cooled high-temperature reactor (KP-FHR). ETU, the largest FLiBe molten salt system ever built, is a non-nuclear prototype of the 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 advanced 140 MWe reactor will use 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.

Kairos Power manufactured 14 tonnes of FLiBe for ETU at its Molten Salt Purification Plant in Elmore, Ohio. “Gaining experience with FLiBe production and operations is fundamental to taking risk off the table towards KP-FHR commercialisation,” said Mike Laufer, Kairos Power co-founder and CEO. “Iterative development with real hardware systems like ETU 1.0 is a pillar of our strategy to deliver a clean, safe, affordable technology with true cost certainty and, when combined with in-house manufacturing, provides a unique opportunity to move quickly so we can make an impact in the fight against climate change.”

The Hermes project is part of the US Department of Energy’s (DOE’s) Advanced Reactor Demonstration Programme. Kairos Power plans to operate the ETU for about five months before decommissioning the unit and constructing a second iteration, ETU 2.0. The company plans to build a third iteration in Oak Ridge in 2024 to lay the groundwork for Hermes operations starting in 2026. Kairos optimistically says the KP-FHR commercial reactor could be operational in the early 2030s.

The US Nuclear Regulatory Commission (NRC) recently issued a construction permit to Kairos Power for the c proposed Hermes non-power test reactor to be built at the Heritage Center Industrial Park in Oak Ridge. The permit authorises Kairos to build a 35 MWt reactor that would use molten salt to cool the reactor core. Kairos will have to submit a separate application for an operating licence.

Image: The Engineering Test Unit at Kairos Power's testing and manufacturing facility in Albuquerque, New Mexico (courtesy of Kairos Power)

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