Simulation of the JT-60SA supercritical helium cooling loops during magnet integrated commissioning using Simcryogenics

Abstract The JT-60SA tokamak fusion experiment is under final commissioning in Naka, Japan. The magnetic confinement of this fusion facility is performed by superconducting magnets cooled to around 4.5 K. These magnets are kept in their superconducting state by a forced-flow circulation of supercritical helium (SHe) ensured by two separate cooling loops. The SHe flows through these loops by means of cryogenic circulators ensuring a flow rate of around 950 g/s, maintaining a temperature of around 4.5 K at the magnets’ inlet. The first loop refrigerates the Toiroidal field (TF) magnets in parallel and, in series, their structures and the Central Soleinoid (CS) structures. The second loop refrigerates the 4 CS and the 6 Equilibrium Field (EF) magnets in parallel. A cryogenic plant capable to extract about 9 kW at 4.5 K (equivalent exergetic power) removes the heat deposited in or generated by the magnets and their structures through the SHe loops. This work presents the thermal-hydraulic model of the SHe cooling loops and the superconducting magnets circuits to predict their behavior, particularly in the event of a fast safety discharge (FSD). The modelling of the loops is made using Simcryogenics, a cryogenic simulation tool developed by CEA/DSBT. This modelling is a step towards the complete modelling of the entire cryo-magnetic system of JT-60SA, aiming to improve the control of key variables for more reliable operation. This work has been carried out within the framework of the EUROfusion Consortium, funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No 101052200 — EUROfusion).