Effects of size and static temperature exposure on the shear strength of tungsten bonded CFC blocks for divertor in JT-60SA

•Some silicide materials are found out as insert materials for the fabrication of W/CFC blocks. WSi2 do not exceed but are the same level as insert material as that of SiC + additives.•Zr and V behave as insert materials for W/CFC bonding, but the thermal stability of specimens is not enough.•The bonding strength near edge of an expected size of mono-block is not enough. It needs to be fabricated as a larger size block with 40 MPa of pressure and removed its near-edge parts. The construction of a satellite tokamak, JT-60SA, was completed in 2020. JT-60SA is expected to contribute the research of ITER and developments for DEMO. JT-60SA employs carbon and carbon fiber strengthened carbon (CFC) composites divertors. The divertors will be set on an actively cooled cassette and be remotely handled because of human access restriction into the vacuum vessel due to the radioactivation caused by repeated deuterium plasma operations. An important mission of JT-60SA is high-β steady state plasma research, and during the mission, the use of carbon divertors will be continued. The possibility of metal wall experiments after the complete of high-β steady state plasma research is under discussion. Then the use of remote handled divertor cassette will be a condition, therefore, high performance and appropriate weight divertors are convenient for the operation. One idea is to use clad plates of tungsten and CFC. In previous researches revealed that a sinter bonding method using an insert material of SiC powders + additives was able to join W and CFC. But the research accidentally found out the insert material without explore of the other materials and the size of specimens was small. In present research, some candidates for the insert material were investigated and also the uniformity of strength on a W/CFC block of the expected size were evaluated.