Safety design of radiation shielding for JT-60SA

The radiation shielding, nuclear heating, absorbed dose of the insulator and dose rate have been evaluated for the superconducting tokamak JT-60SA. The shielding structure consists of double wall using the 24 mm thickness of SS316L filled with the 140 mm thickness of borated water (40 °C, 95% 10B enriched). The maximum nuclear heating of the winding at the inboard side of the superconducting TF coil was suppressed to be lower than 0.3 mW/cc. The absorbed dose of the insulator on the in-vessel coil was estimated to be 8.5 MGy for 10 years. The insulators are not necessary to be exchanged with 10 years operation on JT-60SA. The dose rate of JT-60SA site boundary is estimated to be 144 μSv/3 months, and it satisfies the legal limit of 250 μSv/3 months without any additional shielding performance for the JT-60 building.