Thermal-Hydraulic Analysis of the EU DEMO Helium-Cooled Pebble Bed Breeding Blanket Using the GETTHEM Code

The general tokamak thermal-hydraulic model (GETTHEM) has been updated to the most recent version of the EU DEMO helium-cooled pebble bed breeding blanket (BB) design. The GETTHEM results are first benchmarked in a controlled case against the results of 3-D computational fluid-dynamics computations, showing an acceptable accuracy despite the inherent simplifications in the GETTHEM model. GETTHEM is then applied to the evaluation of the poloidal hot spot temperature distribution in an entire BB segment, showing that the maximum temperature in the EUROFER structures overcomes the design limit of 550 °C by more than 50 °C in some blanket modules. A possible mitigation strategy is then proposed and analyzed, based on the idea of cooling the first wall in parallel with the breeding zone, showing that this solution would allow having the EUROFER in its working temperature range in the entire segment, although at the expense of a larger pressure drop

Modelling an in-vessel loss of coolant accident in the EU DEMO WCLL breeding blanket with the GETTHEM code

One of the accidents to be analyzed for the operation of the EU DEMO tokamak reactor is the in-vessel Loss-Of-Coolant Accident (LOCA), in which a postulated rupture in the First Wall causes a rapid pressurization of the Vacuum Vessel (VV). To avoid rupture of the VV, a VV Pressure Suppression System (VVPSS) is used, which is aimed at removing the coolant from the VV, preserving its integrity and safely storing the coolant together with the radioactive products contained therein. A system-level tool for the analysis of thermal-hydraulic transients in tokamak fusion reactors, called GEneral Tokamak THErmal-hydraulic Model (GETTHEM), is under development at Politecnico di Torino. This paper presents the GETTHEM module developed for the description of the EU DEMO VVPSS, in the case of a water-cooled Breeding Blanket concept; the code validation against experimental data coming from the Ingress of Coolant Event campaign performed in Japan is shown. The tool is then applied to a parametric analysis relevant for an EU DEMO in-VV LOCA, and the results are presented and discussed

Numerical Studies on the Influence of Cavity Thermal Expansion on the Performance of a High-Power Gyrotron

An iterative procedure is described, which models the influence of the thermal expansion of the gyrotron cavity on the expected gyrotron performance. It is a multiphysics simulation method, which involves electrodynamic, thermal-hydraulic, and thermo-mechanical simulations. The method is applied to the first European 170-GHz, 1-MW continuous wave prototype gyrotron for the ITER. According to the simulations, a performance reduction of 15% is expected at nominal operating parameters, because of the thermal expansion of the cavity. Alternative operating points to mitigate this effect are proposed and numerically validated. The numerical results are discussed in light of experimental findings

Recent progress in the upgrade of the TCV EC-system with two 1MW/2s dual-frequency (84/126GHz) gyrotrons

The upgrade of the EC-system of the TCV tokamak has entered in its realization phase and is part of a broader upgrade of TCV. The MW-class dual-frequency gyrotrons (84 or 126GHz/2s/1MW) are presently being manufactured by Thales Electron Devices with the first gyrotron foreseen to be delivered at SPC by the end of 2017. In parallel to the gyrotron development, for extending the level of operational flexibility of the TCV EC-system the integration of the dual-frequency gyrotrons adds a significant complexity in the evacuated 63.5mm-diameter HE11 transmission line system connected to the various TCV low-field side and top launchers. As discussed in [1], an important part of the present TCV-upgrade consists in inserting a modular closed divertor chamber. This will have an impact on the X3 top-launcher which will have to be reduced in size. For using the new compact launcher we are considering employing a Fast Directional Switch (FADIS), combining the two 1MW/126GHz/2s rf-beams into a single 2MW rf-beam

Contrôle non destructif par thermographie infrarouge des composants face au plasma des machines de fusion contrôlée (modélisation et traitement statistique du signal associé)

In Plasma Facing Components (PFCs) the joint of the CFC armour material onto the metallic CuCrZr heat sink needs to be significant defects free. Detection of material flaws is a major issue of the PFCs acceptance protocol. A Non-Destructive Technique (NDT) based upon active infrared thennography allows testing PFCs on SATIR tests bed in Cadarache. Up to now defect detection was based on the comparison of the surface temperature evolution of the inspected component with that of a supposed "defect-free" one (used as a reference element). This work deals with improvement of thermal signal processing coming from SATIR. In particular the contributions of the thermal modelling and statistical signal processing converge in this work. As for thermal modelling, the identification of a sensitive parameter to defect presence allows improving the quantitative estimation of defect Otherwise Finite Element (FE) modelisation of SATIR allows calculating the so called deterministic numerical tile. Statistical approach via the Monte Carlo technique extends the numerical tile concept to the numerical population concept. As for signal processing, traditional statistical treatments allow a better localization of the bond defect processing thermosignal by itself, without utilising a reference signal. Moreover the problem of detection and classification of random signals can be solved by maximizing the signal-to-noise ratio. Two filters maximising the signal-to-noise ratio are optimized: the stochastic matched filter aims at detects detection and the constrained stochastic matched filter aims at defects classification. Performances are quantified and methods are compared via the ROC curves.La fabrication des Composants Face au Plasma (CFP) d'une machine de fusion contrôlée comporte la réalisation d'une jonction carbone/cuivre qui peut présenter des défauts. La qualification des CFP par des méthodes de Contrôle Non Destructifs (CND) est essentielle.A Cadarache le banc SATIR (Station d'Acquisition et de Traitement Infrarouge) utilise la thermographie infrarouge stimulée pour le CND des CFP : la présence d'un défaut doit être détectée par analyse des mesures IR. Les traitements existants, qui utilisent une référence expérimentale, ont mis en évidence leurs limites. L'amélioration des traitements des mesures SATIR font l'objet de cette thèse. On s'est proposé de faire converger les contributions apportées par la modélisation thermique et par le traitement statistique du signal. Grâce à la modélisation thermique des paramètres sensibles aux défauts ont été identifiés. La détection rapide d'un défaut s'est faite par l'estimation de la résistance thermique de contact De plus, une modélisation du système SATIR par Eléments Finis a permis de définir le concept de tuile synthétique déterministe. Ce concept a été étendu par l'approche statistique (Méthode de Monte Carlo) vers celui de population test numérique. Pour ce qui concerne le traitement du signal, les méthodes statistiques traditionnelles ont permis de s'affranchir du concept de référence expérimentale. De plus le Filtre Adapté Stochastique et ses extensions ont permis d'améliorer les résultats en détection et d'introduire le concept de classification des défauts. Les performances des méthodes à sous-espace ont été quantifiées à l'aide des Courbes Opérationnelles de Réception.TOULON-BU Centrale (830622101) / SudocSudocFranceF