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Title: Design and optimization of Artificial Neural Networks for the modelling of superconducting magnets operation in tokamak fusion reactors

Abstract

In superconducting tokamaks, the cryoplant provides the helium needed to cool different clients, among which by far the most important one is the superconducting magnet system. The evaluation of the transient heat load from the magnets to the cryoplant is fundamental for the design of the latter and the assessment of suitable strategies to smooth the heat load pulses, induced by the intrinsically pulsed plasma scenarios characteristic of today's tokamaks, is crucial for both suitable sizing and stable operation of the cryoplant. For that evaluation, accurate but expensive system-level models, as implemented in e.g. the validated state-of-the-art 4C code, were developed in the past, including both the magnets and the respective external cryogenic cooling circuits. Here we show how these models can be successfully substituted with cheaper ones, where the magnets are described by suitably trained Artificial Neural Networks (ANNs) for the evaluation of the heat load to the cryoplant. First, two simplified thermal-hydraulic models for an ITER Toroidal Field (TF) magnet and for the ITER Central Solenoid (CS) are developed, based on ANNs, and a detailed analysis of the chosen networks' topology and parameters is presented and discussed. The ANNs are then inserted into the 4C model of themore » ITER TF and CS cooling circuits, which also includes active controls to achieve a smoothing of the variation of the heat load to the cryoplant. The training of the ANNs is achieved using the results of full 4C simulations (including detailed models of the magnets) for conventional sigmoid-like waveforms of the drivers and the predictive capabilities of the ANN-based models in the case of actual ITER operating scenarios are demonstrated by comparison with the results of full 4C runs, both with and without active smoothing, in terms of both accuracy and computational time. Exploiting the low computational effort requested by the ANN-based models, a demonstrative optimization study has been finally carried out, with the aim of choosing among different smoothing strategies for the standard ITER plasma operation.« less

Authors:
; ; ; ; ;
Publication Date:
OSTI Identifier:
22572350
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Computational Physics; Journal Volume: 321; Other Information: Copyright (c) 2016 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ACCURACY; DESIGN; HEATING LOAD; ITER TOKAMAK; NEURAL NETWORKS; OPTIMIZATION; PLASMA; PULSES; SIMULATION; SOLENOIDS; SUPERCONDUCTING MAGNETS; THERMAL HYDRAULICS; WAVE FORMS

Citation Formats

Froio, A., Bonifetto, R., Carli, S., Quartararo, A., Savoldi, L., E-mail: laura.savoldi@polito.it, and Zanino, R. Design and optimization of Artificial Neural Networks for the modelling of superconducting magnets operation in tokamak fusion reactors. United States: N. p., 2016. Web. doi:10.1016/J.JCP.2016.05.028.
Froio, A., Bonifetto, R., Carli, S., Quartararo, A., Savoldi, L., E-mail: laura.savoldi@polito.it, & Zanino, R. Design and optimization of Artificial Neural Networks for the modelling of superconducting magnets operation in tokamak fusion reactors. United States. doi:10.1016/J.JCP.2016.05.028.
Froio, A., Bonifetto, R., Carli, S., Quartararo, A., Savoldi, L., E-mail: laura.savoldi@polito.it, and Zanino, R. Thu . "Design and optimization of Artificial Neural Networks for the modelling of superconducting magnets operation in tokamak fusion reactors". United States. doi:10.1016/J.JCP.2016.05.028.
@article{osti_22572350,
title = {Design and optimization of Artificial Neural Networks for the modelling of superconducting magnets operation in tokamak fusion reactors},
author = {Froio, A. and Bonifetto, R. and Carli, S. and Quartararo, A. and Savoldi, L., E-mail: laura.savoldi@polito.it and Zanino, R.},
abstractNote = {In superconducting tokamaks, the cryoplant provides the helium needed to cool different clients, among which by far the most important one is the superconducting magnet system. The evaluation of the transient heat load from the magnets to the cryoplant is fundamental for the design of the latter and the assessment of suitable strategies to smooth the heat load pulses, induced by the intrinsically pulsed plasma scenarios characteristic of today's tokamaks, is crucial for both suitable sizing and stable operation of the cryoplant. For that evaluation, accurate but expensive system-level models, as implemented in e.g. the validated state-of-the-art 4C code, were developed in the past, including both the magnets and the respective external cryogenic cooling circuits. Here we show how these models can be successfully substituted with cheaper ones, where the magnets are described by suitably trained Artificial Neural Networks (ANNs) for the evaluation of the heat load to the cryoplant. First, two simplified thermal-hydraulic models for an ITER Toroidal Field (TF) magnet and for the ITER Central Solenoid (CS) are developed, based on ANNs, and a detailed analysis of the chosen networks' topology and parameters is presented and discussed. The ANNs are then inserted into the 4C model of the ITER TF and CS cooling circuits, which also includes active controls to achieve a smoothing of the variation of the heat load to the cryoplant. The training of the ANNs is achieved using the results of full 4C simulations (including detailed models of the magnets) for conventional sigmoid-like waveforms of the drivers and the predictive capabilities of the ANN-based models in the case of actual ITER operating scenarios are demonstrated by comparison with the results of full 4C runs, both with and without active smoothing, in terms of both accuracy and computational time. Exploiting the low computational effort requested by the ANN-based models, a demonstrative optimization study has been finally carried out, with the aim of choosing among different smoothing strategies for the standard ITER plasma operation.},
doi = {10.1016/J.JCP.2016.05.028},
journal = {Journal of Computational Physics},
number = ,
volume = 321,
place = {United States},
year = {Thu Sep 15 00:00:00 EDT 2016},
month = {Thu Sep 15 00:00:00 EDT 2016}
}