The plasma facing walls in the fusion reactor suffer extremely high heat and particle load from a high temperature plasma. In the subject of “development of the high heat flux component”, the divertor heat removal component which exposed to the highest heat loading have been developed. The basic concept of this component is that a water-cooled copper alloy heat sink is bonded on behind of a tungsten armour material. We have successfully developed a new type of divertor heat removal component with ultra-high heat removal performance by “advanced multi-step brazing (AMSB)” to date, in which the AMSB originally developed by our research group. In the subject of “plasma wall interaction”, formation mechanism of the radiation defects in the plasma facing walls due to the high-heat and -particle load have investigated by using a transmission electron microscope (TEM) and other analytical instruments.