Evaluation of heat removal property in W/Cu/RAFM steel joint by using electron beam facility

Abstract

• The durability of the W/Cu/JLF-1 joint sample fabricated by brazing was confirmed by performing steady-state and repetitive heat loading experiments. • The W/Cu/JLF-1 showed excellent heat removal performance under the steady-state heat loading. • A degradation of the heat removal performance was confirmed during the repetitive heat loading. • The delamination which could lead to the barrier of efficient heat transfer was confirmed after the repetitive heat loading of ∼6.0 MW/m 2 . A reliable technique for creating joints between tungsten (W) and Reduced Activated Ferritic/Martensitic (RAFM) steel with a pure-copper (Cu) interlayer (W/Cu/RAFM steel) has been explored for developing the heat removal component in the baffle and dome of a divertor. The first joint sample of W/Cu/RAFM steel was fabricated by using a brazing technique described in our previous work. In this work, to evaluate the heat removal property, a joint sample was subjected to a steady-state and a repetitive heat loading test with an electron beam facility (ACT2). In the steady-state heat loading test, a step-wised static heat load with ∼0.7, ∼1.0, ∼1.9, ∼2.7, ∼3.6, ∼4.4 and ∼6.0 MW/m 2 was applied to the joint sample. The temperatures on the W and RAFM steel showed a linear increasing tendency, as a function of the heat loading value. Also, in the repetitive heat loading test, a 30 s pulse width of 100 cycles was applied with a maximum heat loading value of ∼2.8 and ∼6.0 MW/m 2 . The obvious temperature excursion, while increasing the heat cycles, was confirmed at ∼6.0 MW/m 2 . After the heat loading, a major crack in the vicinity of the interface between the W and Cu was confirmed. This crack led to the degradation of the heat removal performance over ∼6.0 MW/m 2 .