Prediction, experimental results and analysis of the ITER TF insert coil quench propagation tests, using the 4C code

Abstract

The ITER Toroidal Field Insert (TFI) coil is a single-layer Nb 3 Sn solenoid tested in 2016-2017 at the National Institutes for Quantum and Radiological Science and Technology (former JAEA) in Naka, Japan. The TFI, the last in a series of ITER insert coils, was tested in operating conditions relevant for the actual ITER TF coils, inserting it in the borehole of the Central Solenoid Model Coil, which provided the background magnetic field. In this paper, we consider the five quench propagation tests that were performed using one or two inductive heaters (IHs) as drivers; out of these, three used just one IH but increasing delay times, up to 7.5 s, between the quench detection and the TFI current dump. The results of the 4C code prediction of the quench propagation up to the current dump are presented first, based on simulations performed before the tests. We then describe the experimental results, showing good reproducibility. Finally, we compare the 4C code predictions with the measurements, confirming the 4C code capability to accurately predict the quench propagation, the evolution of total and local voltages, as well as of the hot spot temperature. To the best of our knowledge, such a predictive validation exercise is performed here for the first time for the quench of a Nb 3 Sn coil. Discrepancies between prediction and measurement are found in the evolution of the jacket temperatures, in the He pressurization and quench acceleration in the late phase of the transient before the dump, as well as in the early evolution of the inlet and outlet He mass flow rate. Based on the lessons learned in the predictive exercise, the model is then modified to try and improve a posteriori (i.e. in interpretive, as opposed to predictive mode) the agreement between simulation and experiment.

Forced flow cryogenic cooling in fusion devices: A review

“…The thermo-hydraulic validation of the code has also done for the 25kA safety discharge of the TFMC [ 44 ]. The 4C code has been rigorously validated for various SC magnet system [ 43 , 44 , 45 , 46 , 47 , 48 , 49 ] including even predictive validation where the simulations are performed before/without the knowledge of the results of the measurements [ 50 ]. The rigorous validation activity carried out on 4C code puts it in a different perspective with respect to the others.…”

Metamodeling and On-Line Clustering for Loss-of-Flow Accident Precursors Identification in a Superconducting Magnet Cryogenic Cooling Circuit

“…Finally, an analysis of the plasma quench propagation tests in the ITER TF insert coil is developed in ref. [27].…”

A new model for the analysis of quench in HTS cable-in-conduit conductors based on the twisted-stacked-tape cable concept for fusion applications

“…This is because various tools are already available, see for example the 4C [28], VENECIA [29] and THEA [30] codes, and in some cases they are also extensively validated, see e.g. [31]. In that respect, a few attempts to model HTS CICC have already been made, adopting the same tools and the same approach used for LTS CICC, see for example [32], without, however, a full assessment of the validity of the assumptions of such models, when applied to well-known transients but very different conductor layouts.…”