FEM-DBEM procedure for crack analysis in baffle module of Wendelstein 7-X

摘要

"Wendelstein 7-X" is the world's largest nuclear fusion experiment of "stellarator type" in which a hydrogen plasma is confined in a magnet field, generated with external superconducting coils, allowing the plasma to be heated up to fusion temperature. The water-cooled Plasma Facing Components (PFC) protect the Plasma Vessel (PV) against radiative and convective heat from the plasma. After the manufacturing process of the heat shields and baffles, several cracks have been found in the braze and in the cooling pipes. Due to heat loads occurring during each Operational Phase (OP), thermal-stresses are generated in the heat sinks, brazes and cooling pipes, that encourage cyclic crack-growth and, eventually, the water leak through the pipes. The aim of this study is to predict the operational limits of the baffles and heat shields under cyclic heat loads, by using a numerical model based on a FEM-DBEM approach, in order to provide an assessment on the risks of premature failure for segments assembled in the PV.