AbstractConceptual design studies of nuclear shielding and fuel cycle based on nuclear safety aspects are presented for the steady-state tokamak device JT-60 Super Upgrade (JT-60SU). Combination of tungsten and SS-316 materials is newly proposed for the candidate vessel material in addition to the titanium alloy which is chosen as the low activation material so far in JT-60SU. This proposal also meets the design requirements of the nuclear shielding for a D-D neutron production rate of 1×1018 s−1. The fuel cycle and tritium recovery system are designed for steady-state operation with the annual tritium production of 0.2 g and gas flow rate of 20 Pa m3 s−1, most of which is deuterium gas. Concepts of a multiple-barrier tritium containment system and room isolation system are employed for safe tritium processing in the system, which can prevent leakage and propagation to the environment in the case of accidental tritium release.