Design verification of the heating neutral beam port liner for the ITER vacuum vessel

The ITER vacuum vessel provides a high quality vacuum for the plasma, as well as the first confinement barrier of radioactive materials. It has upper, equatorial and lower port structures used for equipment installation, utility feedthroughs, vacuum pumping, and access inside the vessel for maintenance. The heating neutral beam (HNB) ports are located side by side at two equatorial ports and provide a path of neutral beam (NB) for plasma heating and current drive. An internal duct liner around the NB is built in the HNB ports, and special panels with tubes armored by copper tiles are placed in the top and bottom of the liner to protect duct surface from high-power heat loads. A global HNB liner model including panels, bulk shielding and tube shielding has been developed, and conjugate heat transfer analyses have been performed to find out pressure drop and heat transfer characteristics of the liner. Heat loads such as NB power, volumetric heating and surface heat flux without beam steering and misalignment are applied in the analyses. Particularly, severe NB power conditions such as local increment due to the tile displacement and peak NB power are considered. Local flow distributions and pressure drop values at each header and branch of the tube are obtained by applying three different coolant flow rates. Together with the coolant flow field, temperature and heat transfer coefficient distributions are also acquired. Utilizing temperature gradient data of the panels, thermal stress analyses have been conducted for various analysis conditions. As results of the thermo-hydraulic and the thermal stress analyses, the overall design adequacy of the HNB liner has been evaluated.