Thermo-Hydraulic Modeling of JT-60SA TF02 Coil and Feeder for First Operation Predictions

During the commissioning phase of JT-60SA magnet system, which included the cool-down in 2020 and the energization of the 18 Toroidal Field (TF) coils up to a nominal current of 25.7 kA in 2021, the combined helium flow issued from TF02 coil and feeder outlet showed a higher temperature profile than the one of the other TF coils when energized, pointing to the presence of an extra joint resistance in the TF02 and associated feeder circuit. To analyze this temperature excursion and the potential associated risks, the TF02 hydraulic circuit and feeder have been modelled with the thermo-hydraulic CryoSoft suite in the framework of a collaboration between Fusion for Energy and CEA. This paper describes the different numerical models developed along with simplifying analytical strategies, comprising detailed THEA models of the TF02 feeder and a model of the TF02 hydraulic circuit in FLOWER. These models consider the variable thermal and hydraulic geometry along the feeder length, include static and transient heat loads from different sources, and account for the heat exchange between the feeder and the TF02 Lateral Pancake at the feeder Terminal Joint (TJ), thus enabling a detailed description of the helium temperature variations in the system. In addition to the static energization load, the discharge of the Equilibrium Field coils has been modelled and its impact on the helium temperature at the outlet and feeder TJ analyzed. Model results show that the temperature excursion due to a faulty joint in the feeder should not put at risk the operation of TF02 coil.