Effects of seismic isolation on the dynamic behaviour of the DTT torus complex during earthquake events

The Divertor Tokamak Test (DTT) fusion machine is currently under construction at ENEA site in Frascati (Italy). The location has been identified as being at high seismic risk. Preliminary analyses, using both static equivalent and dynamic methods, of seismic effects from local response spectra have been carried out on the structure, namely the cryostat base, supporting the vacuum vessel, the magnets and the cryostat, and a reference design has been obtained. An update of the geological seismic surveys for the site showed a more severe local seismic response than previously considered. The analyses based on the updated seismic response revealed potential structural criticality for the base. Therefore, two possible seismic isolation solutions were considered to reduce the stress state. Finally, a comparison in terms of displacement and stress fields between the non isolated configuration and the two isolated ones is presented.