Gyrotron devices use the phenomenon of electron cyclotron resonance (ECR) for the heating of plasma in fusion reactors. A substantial amount of power, carried by the electron beam, is not actively employed and must be exhausted by the gyrotron’s beam collector. In this thesis, the commercial softwares STAR-CCM+ and Ansys are used to carry out a thermo-hydraulic and thermo-mechanical analysis on the collector of the TH1509U-A gyrotron, manufactured by THALES for the Divertor Tokamak Test (DTT) facility in Frascati. The component has a concentric cylindrical shells structure, and it is cooled by subcooled pressurized water flowing into the annular section between the shells.