The chapter deals with the use and production of tritium in tokamak fusion device. The tokamak is a torus shaped magnetic confinement device in which a combination of toroidal and poloidal magnetic fields confines the hot plasma inside a torus-shaped vacuum vessel. In a reactor it is necessary to confine the energy of sufficiently dense plasma for a time allows to an adequate fraction of the fuel to react. The most promising configuration for future controlled thermonuclear fusion reactor, at least for the first generation, is based on deuterium (D)-tritium (T) cycle in a tokamak type machine. In order to induce the D-T fusion it is necessary to overcome the mutual repulsion of the positive charges of the reacting nuclei. In thermonuclear fusion device this energyis supplied by heating the fuel at temperature higher than 10 keV. At those energies, the reactants are fully ionized and form a plasma, which must be confined to be kept away from the walls of the vessel, e.g. applying magnetic fields in a proper configuration. During the D-T fusion the products of the reactions, alpha and neutrons, undergo different behaviour.The alpha particles are trapped by the magnetic fields and transfer their energy to the plasma. Under proper conditions, this internal heating is sufficient to sustain the required temperature and the condition of ignition is reached. Conversely, the neutrons being electrically neutral particles are unaffected by magnetic fields and represent the energy "carriers". In the blanket, a proper component surrounding the vacuum vessel, the fast neutrons are slowed down and their energy is transferred, in form of heat, to a cooling medium and used to drive turbines to generate electricity. To guarantee the self-sufficiency of the reactor the tritium fuel must be produced in the blanket itself through transmutation reactions on lithium. Moreover, under neutron irradiation, the material properties are affected by elemental transmutation and nuclide activation leading to the production of unstable radionuclides, including tritium itself: it leads to a radiation hazard potential both under normal and off-normal operations. © 2013 Nova Science Publishers, Inc. All rights reserved.
|Titolo:||The deuterium-tritium fuel cycle in tokamak devices|
|Data di pubblicazione:||2013|
|Appare nelle tipologie:||2.1 Contributo in volume (Capitolo o Saggio)|