Controlling nuclear fusion reactions to transform their immense power into electric energy has been the challenge and the dream of many scientists for almost a century. Indeed, the nuclear fusion process presents a tempting combination of characteristics, as it exhibits both, high power density and low environmental impact. In the last 60 years, great advances have been achieved in the research field of magnetic confinement fusion reactors. In order to sustain the magneto-hydrodynamic (MHD) stability of confined plasmas, all modern reactors employ Electron Cyclotron Resonance Heating (ECRH) systems, which are capable of generating and directing multiple microwaves beams, of about 1 MW each, in the core of the plasma. These systems use highly reflective steerable mirrors to control the beam direction, in order to follow the movement of local plasma instabilities — called Neoclassical Tearing Modes (NTM) — and achieve their suppression. The aim of this thesis is to provide the conceptual, thermo-mechanical design of a steering launcher system for use in Divertor Tokamak Test (DTT) machine, a bridge reactor between today's most ambitious international project, ITER, and tomorrow's first fusion power plant, DEMO. The design process starts from a discussion of the typical constraints found in thermonuclear reactors. After defining some guidelines about general design decisions, an innovation-oriented approach is followed in the choice of the main features of the system. The thermodynamic analysis of the steering mirror will allow to choose the constructive materials and the configuration of the internal cooling channels. As a further study, an analytical model of mirror's transient thermodynamics will allow to refine the sizing of inlet and outlet cooling tubes, which are critical components for systemic feasibility. On the mechanical side, the choice of in-vessel, piezoelectric actuators will be motivated, while compliant mechanisms will be designed in order to progress towards a friction-free mechanical configuration. A detailed kinematic optimization of the system will be performed, in order to minimize the deformation of the flexible parts and mitigate fatigue failure risk. The present work should be treated as a base for future design improvements in terms of electromagnetic system characterization, thermodynamic optimization, nuclear radiation assessment of the components, and further progress towards a friction-free mechanical configuration.
Controllare le reazioni di fusione nucleare per trasformare la loro immensa potenza in energia elettrica è stata la sfida e il sogno di molti scienziati per quasi un secolo. Infatti, il processo di fusione nucleare presenta un’allettante combinazione di caratteristiche, poiché mostra sia elevata densità di potenza che ridotto impatto ambientale. Negli ultimi 60 anni, sono stati raggiunti grandi avanzamenti nel campo di ricerca dei reattori a confinamento magnetico. Per mantenere la stabilità magneto-fluidodinamica (MHD) del plasma confinato, tutti i reattori moderni sono dotati di sistemi di Electron Cyclotron Resonance Heating (ECRH), che sono in grado di generare e direzionare fasci multipli di microonde da circa 1 MW l’uno verso il nucleo del plasma. Tali sistemi utilizzano specchi mobili ad alta riflettività per controllare la direzione del fascio, in modo da seguire il movimento di instabilità locali del plasma – dette Neoclassical Tearing Modes – e sopprimerle. Lo scopo di questa tesi è fornire il progetto termo-meccanico concettuale di un lanciatore mobile da utilizzarsi nella macchina Divertor Tokamak Test (DTT), un reattore ponte fra il progetto internazionale più ambizioso di oggi, ITER, e il primo impianto a fusione nucleare di domani, DEMO. Il processo di progettazione inizia da una discussione dei vincoli tipici di un reattore termonucleare. Dopo aver definito alcune linee guida riguardo le scelte progettuali generali, verrà seguito un approccio improntato all’innovazione nella scelta delle caratteristiche principali del sistema. L’analisi termodinamica dello specchio mobile consentirà di scegliere i materiali costruttivi e la configurazione dei canali di raffreddamento interni. Come approfondimento ulteriore, un modello analitico della termodinamica transitoria dello specchio permetterà di rifinire il dimensionamento dei canali di entrata e di uscita del fluido refrigerante, componenti cruciali per la fattibilità operativa del sistema. Dal lato meccanico, la scelta di attuatori piezoelettrici interni alla camera a vuoto sarà motivata, mentre verranno progettati dei compliant mechanisms per progredire verso una configurazione meccanica priva di attrito. Un’ottimizzazione cinematica dettagliata verrà eseguita, al fine di minimizzare la deformazione delle parti flessibili e mitigare il rischio di rottura a fatica. Questo lavoro è da intendersi come una base per futuri miglioramenti progettuali in termini di caratterizzazione elettromagnetica del sistema, ottimizzazione termodinamica, verifica della resistenza alle radiazioni dei componenti e ulteriore progresso verso una configurazione meccanica senza attrito.
Design of an ECRH steering launcher for Divertor Tokamak Test machine
BUSI, DANIELE
2018/2019
Abstract
Controlling nuclear fusion reactions to transform their immense power into electric energy has been the challenge and the dream of many scientists for almost a century. Indeed, the nuclear fusion process presents a tempting combination of characteristics, as it exhibits both, high power density and low environmental impact. In the last 60 years, great advances have been achieved in the research field of magnetic confinement fusion reactors. In order to sustain the magneto-hydrodynamic (MHD) stability of confined plasmas, all modern reactors employ Electron Cyclotron Resonance Heating (ECRH) systems, which are capable of generating and directing multiple microwaves beams, of about 1 MW each, in the core of the plasma. These systems use highly reflective steerable mirrors to control the beam direction, in order to follow the movement of local plasma instabilities — called Neoclassical Tearing Modes (NTM) — and achieve their suppression. The aim of this thesis is to provide the conceptual, thermo-mechanical design of a steering launcher system for use in Divertor Tokamak Test (DTT) machine, a bridge reactor between today's most ambitious international project, ITER, and tomorrow's first fusion power plant, DEMO. The design process starts from a discussion of the typical constraints found in thermonuclear reactors. After defining some guidelines about general design decisions, an innovation-oriented approach is followed in the choice of the main features of the system. The thermodynamic analysis of the steering mirror will allow to choose the constructive materials and the configuration of the internal cooling channels. As a further study, an analytical model of mirror's transient thermodynamics will allow to refine the sizing of inlet and outlet cooling tubes, which are critical components for systemic feasibility. On the mechanical side, the choice of in-vessel, piezoelectric actuators will be motivated, while compliant mechanisms will be designed in order to progress towards a friction-free mechanical configuration. A detailed kinematic optimization of the system will be performed, in order to minimize the deformation of the flexible parts and mitigate fatigue failure risk. The present work should be treated as a base for future design improvements in terms of electromagnetic system characterization, thermodynamic optimization, nuclear radiation assessment of the components, and further progress towards a friction-free mechanical configuration.File | Dimensione | Formato | |
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https://hdl.handle.net/10589/151561