Structural analysis of the US ITER central solenoid magnet cryogenic piping system

The Central Solenoid (CS) is the heart of the ITER tokamak and serves as a critical element in the ITER magnet system. The CS consists of a stack of six independently operated high field superconducting magnets (modules), a pre-compression structure, a support system, and a centering system. The CS piping system supplies the modules and support structure with supercritical helium (He) coolant to achieve and maintain the 4 K operating temperature. The CS module piping consists of a system of inlet and outlet pipes that delivers the coolant to the modules and returns it to the cryostat. The CS structure piping supplies coolant from the structure cooling feeder to CS structure components such as key blocks, load distribution plates, and tie plates. The loads on the piping system and its support structure include dead load, internal coolant pressure, seismic accelerations, displacements induced by CS thermal contraction, displacements from electromagnetic (EM) effects on the CS components, and temperature differentials during cooldown and quench. Four different ANSYS® static stress and dynamic modal models apply these loads to determine design-basis stresses and displacements which are used to evaluate the adequacy of the piping system. The piping and support components pass the static stress and fatigue requirements for the respective function and material of each component based on temperature-dependent stress limits. Modal analysis indicates the natural frequency of all the CS cooling system piping lies between 4 Hz and 10 Hz.