Kairos Power Eclipses 40,000 Pebble Mark with New Manufacturing Process

Key Highlights:

• Kairos Power develops new in-house process to manufacture graphite moderator pebbles from surplus blocks of graphite.
• The new workflow enables consistent, high-quality graphite pebble manufacturing to support Engineering Test Unit 2 operations.
• Breakthrough strengthens Kairos Power’s ability to scale critical component production for the company’s advanced reactors.

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Kairos Power produced more than 40,000 solid graphite moderator pebbles using a new manufacturing process at its Manufacturing Development Campus in Albuquerque, New Mexico.  

The pebbles will support the company’s second Engineering Test Unit (ETU 2) hardware demonstration at the site, which will be the world’s largest Flibe molten salt test ever recorded when it starts operations later this year.  

The new technique will also be considered against other in-house production methods to produce moderator pebbles for Kairos Power’s commercial fleet.

Starting from Scratch

The Manufacturing Team started from scratch in early April to create a manufacturing method for solid graphite moderator pebbles using equipment originally designed for machining graphite blocks.  

With no automation or process in place, the team went from concept to production within two weeks—establishing a new capability that transforms flat ET-10 graphite blocks into precision-made spherical pebbles.  

“To start from scratch and build this thing from the ground up speaks volumes to the talent that we have on our Manufacturing Team,” said Gabe Williams, the director for Kairos Power component manufacturing operations. “To reach 40,000 pebbles is a huge achievement that we can continue to iterate and improve upon.”  

“This achievement reflects the kind of rapid, creative problem-solving that Kairos Power thrives on,” said Ed Blandford, co-founder and chief technology officer at Kairos Power. “By developing this manufacturing capability in-house, we can utilize the resources at our Pebble Development Lab more efficiently to lower the risk of delivering a scalable, fuel supply chain for our advanced reactors.”  

How it works

The new process begins with graphite material left over from previous projects that are cut into flat sheets. The sheets are then placed into a milling machine, where custom tooling (designed in-house) removes material to form the spherical shapes. A precision finishing tool then creates the final geometry, producing consistent-high-quality graphite pebbles.

The team also developed specialized systems to protect the quality of the graphite throughout the process including:

• Custom fixtures to securely hold the pebbles during machining
• Tooling management procedures to prevent defects
• Vacuum-based handling systems to improve efficiency

Supporting Reactor Development

The Manufacturing Team produced more than 40,000 graphite moderator pebbles that were successfully loaded into the ETU 2 reactor vessel. The reactor vessel will soon be filled with 16 metric tons of Kairos Power’s Flibe molten salt coolant to help validate primary systems, operations, and manufacturing methods. 

The machined pebbles are helping to supplement surrogate annular fuel pebbles in ETU 2 that were made in the company’s Pebble Development Lab (PDL) in Albuquerque.

The Fuels team has significantly scaled up operations at PDL since ETU 1, moving from manually pressed solid graphite pebbles to an automated process that incorporates a more complex annular layer of surrogate particles to simulate TRISO fuel characteristics during manufacturing.

Moderator pebbles are used in Kairos Power’s advanced reactors to help optimize the core for a sustained chain reaction.

The new manufacturing technique will be compared against other methods to see what best meets the requirements for producing moderator pebbles for Hermes 2 Demonstration Plant in Oak Ridge, Tennessee, and the commercial fleet.  

ETU 2 is a non-nuclear, full-scale, modular integrated hardware system that will help inform the design, build, and operation of the  Hermes 2 plant.  

The hardware demonstration is expected to start operations later this year.