Analysis of Quench Propagation in the ITER Poloidal Field Conductor Insert (PFCI)

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.

Section: Introductionmentioning

confidence: 99%

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

Zanino

Bonifetto

Brighenti

et al. 2018

“…Another important parameter for the assessment of the conductor performance is the minimum quench energy (MQE). Numerous experimental tests and numerical analyses of this parameter have been performed in the past both on individual strands [18,19] and cable in conduit conductors [20][21][22][23]. Selected results of the MQE tests performed on the Nb-Ti CPQS conductors of the ITER Project are reported here, showing the dependence of the MQE on the temperature margin with respect to the current sharing temperature of each conductor.…”

Section: Introductionmentioning

confidence: 99%

Performance analysis of the Nb−Ti conductor qualification samples for the ITER project

Breschi

Carati

Bessette

et al. 2015

The ITER machine will require approximately 275 tons of Nb−Ti strands that will be used in poloidal field (PF) coils, correction coils (CC) and feeder busbars. The performance of all these conductors for the ITER machine is qualified by a short full-size sample (4 m) current sharing temperature (T cs ) test in the SULTAN facility at CRPP in Villigen, Switzerland, at the design operating current and peak field. Three ITER domestic agencies participated in PF conductor fabrication (China, the European Union, Russia) while the conductors for feeder busbars and correction coils are entirely produced by the Chinese domestic agency. Each conductor type was qualified by the ITER International Organization after reaching T cs values in excess of ITER specifications. This qualification enabled the launch of procurement and industrial production of the Nb−Ti cable-in-conduit conductors in each domestic agency. In this paper, we summarize the performance of the qualified Nb−Ti samples of the ITER Project, comparing strand performance with conductor performance. The details of the test results will be discussed in terms of dc performance, ac losses and minimum quench energies of each conductor type.

“…Note that the temperature difference between each strand has a dominant impact on the current redistribution compared to the impact of the magnetic field gradient. However, it has been shown that in peculiar cases the magnetic field gradient can have an impact on the quench modeling [67].…”

Section: Resultsmentioning

confidence: 99%

A critical assessment of thermal–hydraulic modeling of HTS twisted-stacked-tape cable conductors for fusion applications

Zappatore

Fietz

Heller

et al. 2019

Self Cite

Reliable analyses of thermal-hydraulic (TH) transients are becoming fundamental to supporting the design of magnets for fusion applications based on high temperature superconducting (HTS) cable-in-conduit-conductors (CICCs). However, currently available TH codes were developed and validated only for the analysis of magnets wound with low temperature superconductor (LTS) CICCs. In order to confirm the applicability of such tools to HTS CICCs, a two-step strategy is presented in this paper. First, a qualitative assessment of the characteristic time and spatial scales in HTS CICCs, based on the twisted-stacked-tape cable (TSTC) concept, has been performed. It shows that the different geometry and materials of TSTC strands lead to heat transfer time scales on the conductor cross-section, which are comparable to those of fast transients, ranging from milliseconds to few seconds, e.g. quench initiation and propagation as well as AC losses. Therefore, the assumptions of temperature uniformity on the cross-section, typical of the well-established 1D codes developed for LTS magnets, become questionable. A second, quantitative assessment, based on detailed electro-thermal models of the conductor and of the single TSTC strand cross-section, provides guidelines for the development of more reliable 1D models for the analysis of TH transients in HTS fusion magnets.