Kairos Power automates fuel pebble inspections

The automated quality control and tracking system supports Kairos Power’s iterative approach to fuel development by streamlining throughput, strengthening material accountability, and generating data that can inform future pebble manufacturing and handling systems, the company said.

The fluoride salt-cooled high-temperature reactor (KP-FHR) technology being developed by Kairos Power uses molten fluoride salt coolant with "pebbles" of TRISO (tri-structural isotropic) fuel. The company is optimising production methods for the pebbles at its Manufacturing Development Campus, where it is producing solid graphite moderator pebbles as well as annular surrogate fuel pebbles.

The system performs its comprehensive quality checks before pebbles are packed for transport or loaded into testing platforms. Each pebble is measured in real time for diameter, physical geometry, and density to verify compliance with strict manufacturing specifications. High-precision lasers then scan the exterior surface down to the micron level to ensure the pebble’s structural integrity. Finally, the inspected pebble moves to an infrared laser engraving station where three unique data matrix codes (similar to QR codes) are etched into the graphite surfaces. The code links each pebble to an individualised record that logs the pebble’s exact dimensions, density measurements, batch, and inspection status. 

The data feeds into downstream handling systems to help engineers track pebbles through testing and operation. Over time, Kairos says, the markings will help identify different pebble types, provide more accurate fuel-consumption measurements, and enable material accountability during operations.

The company is applying an iterative approach to development, validating both nuclear and non-nuclear systems, continuously learning from each iteration. This process - involving three non-nuclear engineering test units (ETUs), the Hermes 1 non-power-generating demonstration unit and the Hermes 2 power-producing unit - will accelerate commercialisation, Kairos Power says.

By developing automated inspection infrastructure in-house, the company says it can learn from each production campaign to improve manufacturing processes and build the foundational capabilities required for commercial-scale fuel production. The automated system is currently processing pebbles to support upcoming hardware demonstrations, with a near-term target of 70,000 inspected pebbles for testing platforms including the company's second ETU. The same capability will support the future deployment of the Hermes 2 plant, for which Kairos broke ground in Oak Ridge, Tennessee, in April.