Eddy Current Analysis of Large Scale Vacuum Vessel of Fusion Grade Tokamak

Abstract

Considering fast growing energy requirements, there is need for technology which can meet the future energy demands. Fusion energy provides a very competent option for producing large amount of energy. Therefore research is going on worldwide to achieve viable controlled fusion through fusion reactors. Nuclear fusion reactor fuses nuclei of two atoms, typically deuterium and Tritium to release large amount of energy and also a neutron. One method achieving fusion is thermonuclear fusion in which the deuterium-tritium fuel is heated to sufficiently high temperature. This high temperature can be achieved inside plasma. For successful fusion to occur, it is necessary to keep plasma dense and hot long enough to undergo fusion, which is generally known as confinement. There are two major ways of confinement, inertial confinement and magnetic confinement. Magnetic confinement can be achieved in a device called tokamak. In a tokamak, plasma is generated in a vacuum vessel and is confined to a toroidal path by means of magnetic field produced by toroidal and poloidal field coils. A typical tokamak used for nuclear fusion has plasma current of the order of 15 MA for energy production of 500 MW and the size of the torus vacuum vessel containing plasma is typically of around 12m height and 20m outer diameter. The dissertation work includes complete modeling of plasma and vacuum vessel. This has been accomplished using ANSYS in conjunction with modeling software like CATIA available at the institute. Due the Plasma instabilities, plasma is subjected to vertical or radial displacements or disruptions, which induces eddy currents in the surrounding structural components like main vacuum vessel, port structures, port plugs, blanket modules and magnetic coils. These induced eddy currents will interact with the toroidal magnetic field (about 5 T typically for fusion grade tokamaks) resulting in significant forces exerted by them on different structural components of vacuum vessel. Transient analysis for different transient conditions, such as plasma displacement in vertically downward directions and abrupt current disruptions, which reduce current abruptly from normal range of MA to only a few kA in duration of only few milliseconds, has been carried out. Through analyses for these conditions, the eddy currents produced in different components of vacuum vessel have been determined and their patterns have been studied using ANSYS.