Structural analysis of the JT-60SA cryostat vessel body

The JT-60SA cryostat is a stainless steel vacuum vessel (14 m diameter, 16 m height) which encloses the Tokamak providing the vacuum environment (10−3 Pa) necessary to limit the transmission of thermal loads to the components at cryogenic temperature. It must withstand both external atmospheric pressure during normal operation and internal overpressure in case of an accident.The paper summarizes the structural analyses performed in order to validate the JT-60SA cryostat vessel body design. It comprises several analyses: a buckling analysis to demonstrate stability under the external pressure; an elastic and an elastic–plastic stress analysis according to ASME VIII rules, to evaluate resistance to plastic collapse including localized stress concentrations; and, finally, a detailed analysis with bolted fasteners in order to evaluate the behavior of the flanges, assuring the integrity of the vacuum sealing welds of the cryostat vessel body.

► Structural analysis to validate the JT-60SA cryostat vessel body design.
► Design code ASME 2007 “Boiler and Pressure Vessel Code. Section VIII”.
► First buckling mode: load multiplier of 10.644, higher than the minimum factor 4.7.
► Elastic and elastic–plastic stress analysis meets ASME against plastic collapse.
► Bolted fasteners have been analyzed showing small gaps closed by strong welding.