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

The structural design of ferritic steel tiles for ripple reduction of toroidal magnetic field in JT-60U is outlined. The 8Cr–2W–0.2V ferritic steel plates were fabricated and mechanical and the vacuum properties were evaluated to assess the design conditions. Little data scattering among the fabricated plates are observed in yield and tensile strengths at ambient temperature and sufficient strength at the structural integrity at operational temperature of 423 K and 573 K. Vacuum property was measured after baking at 473 K for 40 h. It is similar to that of the conventional stainless steel and almost satisfies the JT-60 standard of the invessel material of the vacuum vessel. The ferritic steel is judged to be installable because the JT-60 baking temperature is 573 K, higher than this test temperature of 473 K, and the residual out-gassing is hydrogen, which is the operation gas.