The draining and drying experiments for the plasma vessel cooling pipes of the Wendelstein 7-X stellarator

This paper reports the results of the draining and drying experiments for the plasma vessel water pipes of Wendelstein 7-X project. W7-X is a new generation type of stellarator which is building at the Max Planck Institute für Plasmaphysic in Greifswald. The temperature of the W7-X plasma vessel is controlled by water cooling flow in welded pipelines. For safe operation during maintenance procedures they need to be drained and dried. The layout of water pipes, which is determined by the complicated shape of plasma vessel, causes that discharging by gravity is not possible. The draining and drying experiments performed at the Max Planck Institute für Plasmaphysik in Greifswald proved different methods to completely fill and remove water from pipes. The results of the experiments have shown the best method for draining and drying water pipes of plasma vessel, the hydraulic parameters to be used and determined the final design of the hydraulic loop.