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

•Design and Manufacturing of large vessels for cryogenic plants.•Design and Manufacturing of a special diffuser as injection system of cold helium 20K.•Results of Fluid dynamic Analyses.•Installation procedure and execution of large vessels on the research site. The JT-60SA Tokamak is provided with a cryogenic system with a refrigeration capacity of 9kW (eqv.) at 4.5K. Before commissioning and during occasional warm-up periods the total 3.6t helium inventory (at ∼1.5Mpa(g)) is stored in six pressure vessels. Each vessel is 22m long, has a diameter of 4m, 250m3 volume, and weighs about 73t. 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 (20K) from the cryogenic system quench line, following a fast discharge of the superconducting coils. A special 18m 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.