Numerical investigation of a brazed joint between W-1%La2O3 and ODS EUROFER components

A modular helium-cooled divertor design HEMJ (helium-cooled modular divertor concept with multiple-jet cooling) for the “post-ITER” demonstration (DEMO) fusion reactor has been developed at the Forschungszentrum Karlsruhe. The design goal is to withstand a surface heat flux of at least 10 MW/m2 at an acceptable pumping power.A conical design of a brazed joint between two structural components of the HEMJ finger module which are made of different materials has been investigated. This new transition piece design should withstand at least 1000 temperature load cycles between operating and room temperatures. Due to the large mismatch of the thermal expansion coefficients (TECs) of the different materials used, high thermal stresses caused by the thermocyclic loads could lead to the plasticization of both materials in the joint region. To demonstrate the feasibility of this transition piece design, a systematic investigation is required, which includes a numerical simulation, the choice of the brazing material, a study of the brazing technology, and thermocyclic tests of the finger mock-up.This paper shall present a method of numerical investigation as the first step of investigation. Plastic stress calculations are performed using the commercial software ANSYS® taking into account thermocyclic as well as internal pressure loads. The calculation results, in particular the plastic behavior of the brazed joint, will be discussed.