Abstract
In order to ensure stable power exhaust and to protect the walls of fusion reactors, liquid metals that are fed to the wall surface through a capillary porous system (CPS) are considered as alternative plasma-facing components (PFCs). However, operational issues like drop ejection and plasma contamination may arise. In this study, the unsteady flow of a liquid metal inside a single pore of the CPS in the presence of Lorentz forces is investigated. A numerical solution is performed via the finite element methodology coupled with elliptic mesh generation. A critical magnetic number is found (Bondm = 4.5) below which the flow after a few oscillations reaches a steady state with mild rotational patterns. Above this threshold, the interface exhibits saturated oscillations. As the Lorentz force is further increased, Bondm > 5.8, a Rayleigh–Taylor instability develops as the interface is accelerated under the influence of the increased magnetic pressure and a finite time singularity is captured. It is conjectured that eventually, drop ejection will take place that will disrupt cohesion of the interface and contaminate the surrounding medium. Finally, the dynamic response of different operating fluids is investigated, e.g., gallium, and the stabilizing effect of increased electrical conductivity and surface tension is demonstrated.
Highlights
IntroductionThermonuclear fusion is perhaps the most promising one since it offers a profuse energy supply without seriously affecting the environment [1,2]
It is widely known that the global oil and gas resources are diminishing, and in order to avoid an energy crisis in the future, alternative sources of energy must be explored and implemented.Thermonuclear fusion is perhaps the most promising one since it offers a profuse energy supply without seriously affecting the environment [1,2]
Assuming a fixed contact point arrangement of the liquid metal at the pore exit where it joins the surrounding medium and the solid substrate, simulations performed in the context of axisymmetry have shown that a critical threshold exists for the magnetic number (Bondm,cr1 = 4.5), below which the interface, after few decaying oscillations as a result of the interaction between the capillary and the Lorentz forces, concludes quite fast (t ~ 1 ms) to a steady state with mild rotational patterns
Summary
Thermonuclear fusion is perhaps the most promising one since it offers a profuse energy supply without seriously affecting the environment [1,2] It is based on the fusion reaction between deuterium and tritium that produces a helium nucleus and a neutron, releasing a high amount of energy. This reaction does not occur spontaneously, but instead a temperature of 150 million degrees Celsius is needed inside the reactor. A magnetic field is usually needed to control the confinement of the plasma in the reactor For these reasons, the design of a fusion reactor is a challenging task and several issues must be addressed before this idea becomes widely applicable. The Eurofusion Plant Physics and Technology Work Program aims at putting in operation a demonstration fusion power reactor (DEMO) by 2050
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