The plasma facing unit (PFU) of ITER divertor is repeatedly exposed to high heat flux, and a reliable heat removal capability is crucial for its adequate performance. The cyclic high heat flux test (HHFT) that has been conducted to evaluate the reliability of PFU reveals that the surface modification and macro-crack formation in W monoblock, which is the plasma facing material, may hinder the operation of fusion reactors. Therefore, optimization of both manufacturing technology and material development is necessary for reliable operation. In this study, we investigate the dependence of material properties on the surface modification and macro-crack formation in W monoblocks. W monoblocks manufactured by two different suppliers were examined, and the results of cyclic HHFT revealed that the heat removal capability was not degraded in all the examined W monoblocks. Further, it was observed that the W monoblock exhibiting characteristic grain structure and tensile property suffered less surface modification without macro-crack formation due to cyclic heat loading.

ITER偏滤器的等离子面对单元（PFU）反复暴露于高热通量中，可靠的除热能力对其适当的性能至关重要。为评估PFU的可靠性而进行的循环高热通量测试（HHFT）显示，作为面向等离子体的材料W单体的表面改性和宏观裂纹的形成可能会阻碍聚变反应堆的运行。因此，为了可靠地运行，必须同时优化制造技术和材料开发。在这项研究中，我们调查了W单体中材料性能对表面改性和宏观裂纹形成的依赖性。检查了两个不同供应商制造的W整体块，循环HHFT的结果表明，在所有检查的W单体中，排热能力均未降低。此外，观察到，表现出特征晶粒结构和拉伸性能的W单体由于循环热负荷而经受较少的表面改性，而没有形成大裂纹。