Measurements of the Effective Thermal Conductivity of the ITER TF Coil Case Cooling System

The ITER magnet system contains 18 toroidal field (TF) coils and each TF winding pack is enclosed in a stainless steel coil case. During operation, the coil case will be subjected to eddy current and nuclear heating, in addition to the static heat loads (thermal conduction and radiation). In order to minimize the heat transfer to the superconducting winding pack, the coil case is cooled by a flow of helium at 4.5 K circulating through an array of cooling pipes. In the baseline design, the thermal contact between the cooling pipes and the coil case is made by a resin bond. A series of samples has been prepared reproducing the geometry of the grooves where the cooling pipes are embedded. The samples explore the baseline design as well as an alternative design based on the contact between metallic surfaces. The effective thermal conductivity has been measured in the SULTAN facility by circulating a constant flow of helium at 4.5 K and applying a steady state heat load. The measurements show no indication of cracks or delamination decreasing significantly the overall heat conductivity of the samples after cool-down, even after a four-point bending process representative of the assembly process.