Coupled thermal-mechanical analysis of two ITER-like first wall mockups under heat shock of plasma disruptions

Abstract

The first wall of the fusion reactor is a plasma-facing component and is a key link to maintain the integrity of structure during thermal shock induced by plasma disruptions. Be and W/Cu functionally graded materials are two kinds of important plasma-facing materials (PFM) of first wall in fusion reactor currently. Previous researches seldom comparatively evaluated the normal servicing and heat shock resistance performance of first walls with those two kinds of PFMs. And also there lacks coupled thermal/mechanical analysis on the heat shock process in consideration of multiple thermal/mechanical phenomena, such as material melting, solidification, evaporation, etc., which is significant to further understand the heat shock damage mechanism of the first wall with different PFMs. With the aim of learning more detailed mechanical mechanism of thermal shock damage and then improving the thermal shock resistance performance of different first wall designs, the coupled thermal/mechanical response of two typical ITER-like first walls with PFM of Be and functionally graded W-Cu respectively under the heat shock of 1–2 GW/m2 are computed by the finite element method. Special considerations of elastic-plastic deformation, material melting, and solidification are included in numerical models and methods. The mechanical response behaviors of different structures and materials under the normal servicing operation as well as plasma disruption conditions are analyzed and investigated comparatively. The results reveal that heat is mainly deposited on the PFM layer in the high energy shock pulse induced by plasma disruptions, resulting in complex thermal stress change as well as mechanical irreversible damage of thermal elastic and plastic expansion, contraction and yielding. Compared with the first wall with Be PFM, which mitigates the damages from heat shock at most only in the PFM layer with cost of whole PFM layer plastic yielding, the first wall with graded W-Cu PFM is demonstrated to be possessed both of higher heat shock resistance performance and normal servicing performance, provided its material gradient and cooling capacity are well optimized under practical loading conditions.