The scope of this procurement procedure is the design, manufacturing, assembly, factory acceptance testing, transport and delivery of the Helium Refrigeration System (HRS) for the Isotope Separation System (ISS) within the Tritium Plant at ITER, based on Reversed Turbo-Brayton technology. The HRS will supply a cooling net power of approximately 1500 W at 18.5 K for the ISS of the ITER Tritium Plant. Optional scope: Option 1: factory performance testing; Option 2: technical assistance for on-site installation and final connection activities; Option 3: technical assistance for commissioning and site acceptance testing. Before the final call for tender, F4E may decide to remove certain options from the scope.