Investigation of fabrication technologies for Japanese ITER test blanket module

Hirose, Takanori; Nomoto, Yasunobu; Enoeda, Mikio; Akiba, Masato

161.5mm3500mm cylindrical tubes and 11mm1.5mm3500mm square tubes were successfully fabricated from F82H bullet by cold rolling. The tube is long enough to fabricate the first wall without any joint in the cooling path. The surface roughness (Rz) is less than 1m and it is smooth enough to HIP bonding without further surface finish. As for the HIP pretreatment, the degassing conditions and surface roughness were investigated as parameters of pretreatment conditions in this work. F82H was HIPped with the conditions of 1373K, 150MPa and 2h holding time. Normalizing at 1233K for 0.5h and tempering at 1023K were performed as post-HIP heat treatment. Although tensile property of the HIP joint was not affected by the surface roughness and degassing conditions, the impact property was significantly degraded by lack of degassing. The degradation in impact property was caused by the micro dispersed oxide on the bonding surface. The oxide was decomposed by thermal aging at 1313K and the aging recovered the impact property. Therefore, to complete HIP bonding, degassing conditions must be strictly controlled to avoid the oxidation of bonding surface. And the inappropriately degassed joint should be followed by thermal aging to decompose the oxides.