Characterization of main ion properties for the optimization of future fusion power plants

In the search for a clean and sustainable energy source for our society, fusion energy emerges as a promising candidate. The realization of a fusion power plant on Earth faces important technological and physical challenges. This thesis is a multidisciplinary project that addresses the optimization of future fusion devices from a plasma physics and engineering perspective. From the plasma physics perspective, the performance of future fusion reactors depends on the properties of the plasma, the fusion fuel. The main ion properties (in present experimental devices, deuterium) are particularly important as they determine the fusion power, which sets the electricity production. Traditionally, the main ions have been rarely diagnosed and their properties have typically been inferred from minority impurity measurements and theoretical models. In this thesis, a novel diagnostic method has been established that enables the direct experimental measurement of the main ions with a focus on the plasma edge. The plasma edge is a critical region, as it prescribes the boundary conditions for the plasma core performance, while it must enable a heat exhaust solution that limits the power loads to the plasma facing components, keeping the integrity of the fusion reactor. Plasma edge diagnostics are demanding in terms of spatial and temporal resolution, as they need to resolve fast transient events and strong spatial gradients. From an engineering perspective, the efficiency of the power conversion cycle coupled to a fusion reactor has been studied and optimized to maximize the electric power output. Cogeneration schemes as opportunities for boosting the efficiency of future fusion power plants have also been investigated. In the framework of this thesis, a new edge main ion diagnostic based on the Charge Exchange Recombination Spectroscopy technique has been installed and exploited at the ASDEX Upgrade experimental reactor, a full metal wall device, to provide main ion temperature and toroidal rotation velocity measurements. A new in-vessel optical head has been installed, which covers the outermost plasma region with a resolution down to 3 mm. A forward model, based on the collisional radiative model implemented in the fidasim code, and data analysis tools have been developed to enable an accurate interpretation of the main ion data. These are state-of-the-art measurements of edge deuterium temperature and toroidal rotation profiles in a tungsten environment, which resembles conditions relevant for future fusion reactors. Several experiments have been carried out at the ASDEX Upgrade tokamak to characterize the main ion temperature and toroidal rotation in a variety of plasma conditions. The role of plasma collisionality and heating scheme on the main ion temperature and toroidal rotation has been addressed. The main ion properties have been compared to minority impurity ion and electron measurements and serve as a testbed for theoretical transport models. In particular, the measurements are compared against neoclassical transport theory. The main ion properties in high and low confinement regimes, such as the high confinement mode (H-mode), low confinement mode (L-mode), improved energy confinement mode (I-mode) and quiescent high confinement mode (QH-mode), have been documented. It has been found that the impurity ion temperature does not always give a good description of the main ion properties, and the thermal equilibration between main and impurity ions is a complex function of heating scheme and collisionality. In H-mode, the main ion toroidal rotation is in remarkably good agreement with neoclassical theory in the steep gradient region of the plasma edge. The detailed diagnosis of the edge plasma properties is essential for understanding plasmas in present experimental devices, and consequently, for the projection towards future fusion power plants and their optimization. The integration of a portfolio of Rankine and Brayton power conversion cycles with a fusion reactor has been studied in a framework that couples the engineering equation solver and the process systems code. The fusion reactor is based on the European DEMO Baseline 2018, which sets the temperature and power boundary conditions. In the intermediate temperature range envisaged for the EU-DEMO Baseline 2018, supercritical carbon dioxide power conversion cycles constitute a very attractive technology. Nuclear fusion cogeneration of heat and electricity has been put forward as a strategy for boosting the efficiency of future fusion devices. The use of district heating networks for the recovery of low-grade heat yields efficiency improvements for all power cycle layouts. The economic viability has been studied by the definition of the levelized cost of hybrid production, which is an indicator that integrates cost estimates from process and production and distribution costs. The cogeneration scheme is feasible from an economic point of view for Rankine and supercritical carbon dioxide power cycles. This work expands potential fusion energy applications and its deployment in the energy market.

Author dc:creator

• Cano Megías, Pilar

Advisors dc:contributor.advisor

• Chacartegui, Ricardo
• Viezzer, Eleonora

Statement dc:rights

• Attribution-NonCommercial-NoDerivatives 4.0 Internacional

Licence dc:rights.uri

• http://creativecommons.org/licenses/by-nc-nd/4.0/

Language dc:language.iso

eng

Handle dc:identifier.uri

https://hdl.handle.net/11441/142823

OAI identifier oai:identifier

oai:idus.us.es:11441/142823