Structural analyses are performed on subassemblies of so-called baffle modules, critical plasma facing components of the “Wendelstein 7-X” stellarator, where the presence of detected large cracks can drastically reduce the expected fatigue life. Such baffle modules are designed to remove heat coming from the hot plasma, heated up to nuclear fusion temperatures, and are made of graphite tiles bolted onto a structure of CuCrZr heat sinks that, in turn, are brazed on water-cooled stainless steel pipes. High plastic deformations occurred during the shaping process of the pipes were responsible for crack initiation at the roots of the braze. Such cracks, if propagating under fatigue thermomechanical loads, could penetrate into the cooling pipes and cause leakage of the coolant fluid, with consequent damages and interruption of operations. In this work, the geometry of one of these cracks has been reconstructed by CT scans and analysed using the Dual Boundary Element (DBEM) method, in order to forecast its potential impact on the component life.
Crack modelling in baffle modules of nuclear fusion experiment “Wendelstein 7-x”
LEPORE, MARCELLO ANTONIO;GIANNELLA, VENANZIO;CITARELLA, Roberto Guglielmo
2017-01-01
Abstract
Structural analyses are performed on subassemblies of so-called baffle modules, critical plasma facing components of the “Wendelstein 7-X” stellarator, where the presence of detected large cracks can drastically reduce the expected fatigue life. Such baffle modules are designed to remove heat coming from the hot plasma, heated up to nuclear fusion temperatures, and are made of graphite tiles bolted onto a structure of CuCrZr heat sinks that, in turn, are brazed on water-cooled stainless steel pipes. High plastic deformations occurred during the shaping process of the pipes were responsible for crack initiation at the roots of the braze. Such cracks, if propagating under fatigue thermomechanical loads, could penetrate into the cooling pipes and cause leakage of the coolant fluid, with consequent damages and interruption of operations. In this work, the geometry of one of these cracks has been reconstructed by CT scans and analysed using the Dual Boundary Element (DBEM) method, in order to forecast its potential impact on the component life.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
