Manufacturing and installation of the JT-60SA helium storage vessels for the cryogenic plant

Abstract The JT-60SA Tokamak is provided with a cryogenic system with a refrigeration capacity of 9 kW (eqv.) at 4.5 K. Before commissioning and during occasional warm-up periods the total 3.6 t helium inventory (at ∼1.5 Mpa(g)) is stored in six pressure vessels. Each vessel is 22 m long, has a diameter of 4 m, 250 m 3 volume, and weighs about 73 t. As the vessels will store pure helium, the tightness and cleanliness requirements were quite demanding. One of the vessels is also used to receive the cold helium (20 K) from the cryogenic system quench line, following a fast discharge of the superconducting coils. A special 18 m long helium diffuser system and a thermal barrier connector at the quench line flange have been designed and manufactured to avoid local chilling of the vessel wall below the minimum allowed temperature of the material.