Analysis on nuclear heating in the superconducting coils of HT-7U tokamak fusion device

The HT-7U superconducting tokamak will generate neutrons at a rate of the order of 10¹⁵ per second during the D-D operation with long pulse up to 1000 s. Nuclear heat in the Toroidal Field (TF) and Poloidal Field (PF) coils have been estimated by using the Monte Carlo particle transport code MCNP-4C and the latest version of the Fusion Evaluated Nuclear Data Library (FENDL-2) based on the three-dimensional geometrical configuration. The calculations show that the nuclear heat in the coils originates ∼ 10% from neutron energy deposition and ∼ 90% from induced gamma energy deposition. To reduce the nuclear heat in the superconducting magnets of the TF and PF coils, a double-wall-structured vacuum vessel (VV) with the boronated water layer of thickness of 5 cm is designed to shield against neutron irradiation.