ITER Seismic Isolation Bearings

Precision-Engineered Seismic Isolation Bearings for ITER

493 Seismic Isolation Bearings Installed

The ITER Tokamak, where nuclear fusion experiments take place, is housed in a massive structure measuring approximately 590 feet long, 197 feet wide, and 197 feet high. This facility is built within a large concrete-lined excavation and rests on 493 seismic isolation bearings, each positioned atop structural pedestals to shield the building from earthquake-induced ground motion.

Designed for Long-Term Performance
These seismic isolation bearings were engineered not only to meet strict structural performance standards but also to remain effective over a 60-year service life. The materials used are highly durable, ensuring consistent performance even under extreme conditions.

Advanced Bearing Construction

Each bearing features a layered design: alternating steel plates and polychloroprene rubber provide the necessary isolation. Mortar is injected between two steel bearing plates, which are anchored to the building’s upper and lower structures using steel studs. Each unit measures approximately 43 inches square and 11.2 inches thick.

Compliance with Updated Seismic Standards

During final design stages, additional testing was conducted to meet the newly published EN 15129 standard for seismic protection devices. This standard outlines requirements for functionality, design, materials, manufacturing, testing, installation, and maintenance.

Testing focused on verifying the aging resistance of the polychloroprene material and confirming that the bearings could withstand both static and dynamic loads in all directions—especially the average vertical load of 850 US tons per bearing.

Proven Technology from Previous Projects

Nuvia-Freyssinet previously developed and tested a similar bearing system in 2010 for the Jules Horowitz Reactor, located on the same site. Nearly 200 seismic isolation bearings were installed there to protect against seismic events.

These earlier bearings (measuring 35 inches square and 7.1 inches thick) were also specified for use beneath the Tokamak building to provide consistent seismic isolation.

Material Durability and Fire Resistance

Meeting the aging criteria for polychloroprene was one of the most challenging aspects. Over the 60-year lifespan, the material must not harden more than 40%, as measured by increased horizontal stiffness. Additives were incorporated to enhance resistance to ozone and oxidation, which contribute to material aging.

The selected compound not only meets these durability standards but also offers fire resistance, adding an extra layer of protection in case of hostile events. A comprehensive testing program was conducted to fully characterize the dynamic behavior of the bearings.

Quality Assurance for Nuclear Standards

To meet the rigorous quality demands of the nuclear industry, additional qualification of the production and installation processes was required. This work was carried out by Nuvia, a sister company, ensuring full compliance with industry standards.