Cooling design and analysis of the ITER EC Upper launcher

ITER will be equipped with four EC (Electron Cyclotron) upper launchers of 8 MW microwave power each with the aim to counteract plasma instabilities during operation. The launcher antennas will be installed into four upper ports of the ITER vacuum vessel. All in-vessel microwave components of an EC antenna, comprising several sets of mirrors and waveguides are mounted into so-called upper port plugs. These are basically hollow casks which fit into the ports as cantilevered built-in components, forming thus integrated systems which guarantee optimum performance and simplify assembly and maintenance. During operation the EC upper port plugs will be heated by nuclear heating from neutrons and photons and thermal radiation from the plasma. Also stray radiation and power losses from the MW-system can create local heating of the port plug structure. This is why the port plugs must be equipped with a powerful heat removal system based on cooling water circuits. Beside optimum dissipation of up to 600kW total heat applied to the launcher also good flow characteristics, adequate distribution of coolant in parallel branches and steady temperature gradients between particular cooling water channels must be ensured by design since no flow control systems will be available inside the vacuum vessel. In addition the cooling circuit will also support the commissioning of the system as it will be used to perform the baking of the port plug regarding operation under vacuum. This paper outlines the general layout of the cooling circuits and particular design features of the cooling channels. All relevant results of thermo-hydraulic analyses for different operation scenarios and fault conditions are presented as well as the thermo-mechanical behavior, fatigue limits and manufacturing aspects.