Structural design of ferritic steel tiles for ripple reduction of toroidal magnetic field in JT-60U

Shibama, Yusuke; Arai, Takashi; Miyo, Yasuhiko; Sawai, Tomotsugu; Sakurai, Shinji; Masaki, Kei; Suzuki, Yutaka; Jitsukawa, Shiro; Miya, Naoyuki

The structural design of the tile as a ripple reduction for toroidal magnetic field in JT-60U was outlined. 8Cr-2W-0.2V ferritic steel plates were fabricated and mechanical and vacuum properties were evaluated to assess the design conditions. Tensile properties were uniform in yield and tensile strength at ambient temperature and sufficient strength as the structural integrity at operational temperature of 423 K and 573 K. Vacuum property was measured with the baking at 473 K and similar to the conventional stainless steel but not satisfy the JT-60 standard of the in-situ material of the vacuum vessel. The ferritic steel was judged as an installable because of that the JT-60 baking temperature is 573 K higher than this test temperature of 473 K, and of that residual out-gassing was hydrogen which was the fuel of the operational plasma.