Thermo-mechanical analysis of a W-Ta-ODS divertor transition joint

Development of a robust transition joint between refractory-based PFC components and external cooling piping system is critical for the successful operation of future fusion power reactors. A helium cooled tungsten-based divertor and a steel-based cooling system joint is particularly challenging, due in part to the large mismatch of thermo-physical properties between the materials and because of the high operating temperatures. A strong metallurgical bond is required in such a duplex joint structure. Drawing on broad existing industrial experience, a joint was designed using Ta as a transition material between W and steel. Thermo-structural FEM analyses were performed to investigate the mechanical response of this joint during power-up, steady state, and shut down of divertor operation.