A team of researchers from the University of New Mexico in collaboration with the Department of Nuclear Engineering and Radiological Sciences (NERS) at the University of Michigan received a grant of $380,000 to develop and demonstrate scalable fluoride salt pump seals and bearings for fluoride-salt-cooled, high-temperature reactors (FHRs). The project also involves collaboration with High Temperature System Designs LLC, Wenesco Pumps and Kairos Power, and aims to improve the reliability, safety, design and operation of FHR power plants.

Fluoride-salt-cooled, high-temperature reactors require reliable high-temperature molten salt pumps to ensure their successful deployment. However, developing salt-lubricated bearings for these pumps has been a significant engineering challenge due to material corrosion and thermal distortion. To address this challenge, the research team plans to employ experimental and numerical methods to investigate the static and dynamic performance of fluoride salt-lubricated bearings and high-temperature seals.

Example of an FHR with fluoride salt pump. The Kairos Power FHR is a novel advanced reactor technology that leverages TRISO fuel in pebble form combined with a low-pressure fluoride salt coolant. Source: Kairos Power

One potential solution lies in the use of modern ceramic materials such as silicon carbide and diamond bearings, which are compatible with high-temperature fluoride salts. These materials show promise but have not yet been tested in a prototypical operating environment for FHR applications.

Additionally, the research team will focus on developing high-temperature shaft seals, such as labyrinth, metal bellow and diamond mechanical seals. These seals are crucial for maintaining leak-tightness in the FHR primary pumps, as the high temperatures of the fluoride salts pose challenges in preventing potential gaseous radionuclide releases.

Scaling up the pumps from laboratory size to industrial scale is another significant aspect of the research. The team will investigate the challenges associated with pump scaling and provide guidelines and insights for large-scale pump designs, which will be valuable for FHR developers.

By developing advanced bearings and seals for fluoride salt pumps, this project aims to improve the performance, reliability and safety of FHRs. The outcomes of the research will contribute to the overall advancement of fluoride-salt-cooled, high-temperature reactor power plants, paving the way for their successful implementation in the future. Project funding was awarded in October 2020 with project completion expected by the end of September 2023.