Recovery from a hot water leakage at the tokamak ASDEX upgrade

During a regular vessel baking after a manned access a leakage of a heating/cooling pipe released about 100 l of hot water into the vacuum vessel of ASDEX Upgrade (AUG). Erosion of a ten years old Cu gasket by water during baking causes the leak. At plasma facing components the water steam forms white remnants as it reacted with the boron-hydride layers used for wall conditioning and cause locally oxidation of stainless steel. After cleaning no significant damages remained. As some remote parts of AUG are not heated water condensates at these locations and stays there for weeks. At these ports serious damages was found at certain kinds of electrical feed through and Al gaskets. Completely removal of water within 4 weeks is needed to avoid this kind of problems. To identify and fix the most dominate leak a step-by-step approach was used. After repair AUG was successful operated for 9 months till the next regular maintenance.