Neutronic analyses of ICRF antenna system for CFETR

Ion cyclotron range frequency (ICRF) antenna is one of the effective auxiliary heating systems to maintain the long pulse and high power steady-state operation of fusion reactors. The ICRF antenna has been designed to be introduced into China Fusion Engineering Test Reactor (CFETR) through one upper port, and the front-end will occupy one blanket. Since the antenna faces the plasma directly, it will be irradiated by high flux neutrons. It is necessary to evaluate the irradiation damage of the antenna. Besides, due to a lot of gaps in the antenna system, the neutron leakage will produce irradiation effects on the vacuum vessel (VV) and toroidal field coil (TFC) behind. Thus the shielding performance needs to be evaluated to support the shielding design. [Purpose] This study aims to evaluate nuclear responses of the exposed components of ICRF antenna by neutronic simulation, and provide data for designing the cooling system and estimating its life after irradiation. [Methods] Based on CFETR model of 22.5° fan section water cooled cladding, the neutronic model was converted from CAD file into MCNP input file by cosVMPT software. Nuclear analysis of ion cyclotron heating antenna was performed by using MCNP5 particle transport program and fendl-2.1 database, as well as the variance reduction method of Global Variance Reduction(GVR) "on the fly". The radiation damage and nuclear response of the main components of the antenna, including neutron flux, displacement per atom (DPA), gas production rate and nuclear thermal density, were calculated to provide data for the design and life assessment of the antenna cooling system. [Results & Conclusions] The neutron radiation damage of the vacuum chamber, window and longitudinal field coil at the corresponding position of lead-in antenna is obtained to evaluate whether the shielding meets the requirements of material. In addition, the Tritium Breeding Ratio (TBR) of the whole reactor is decreased from original 1.151 to 1.147 due to the blanket opening, which corresponds to a reduction of 0.35%.