What is Nuclear Fusion?
(Picture Copyright ITER)
Nuclear fusion is the energy-providing process that has been taking place in the sun and stars for billions of years. Under extreme pressure conditions and temperature of about 15 million degrees, the atomic nuclei fuse together there in the so-called plasma. Since the pressure conditions of the sun cannot be realized on the Earth, the reactor temperature has to reach more than 100 million degrees to achieve the plasma state. In order to protect the surrounding reactor walls from the hot plasma, the plasma is confined by a very high magnetic.
In the future fusion power reactors, deuterium and tritium will be used as fusion fuels. The nucleus of heavy hydrogen deuterium fuses with the nucleus of the super heavy hydrogen tritium to helium - 4 nuclei, the so-called α-particles (two protons and two neutrons) decay through the emission of a neutron. 80% of the released energy is bound to the neutron, which escapes the magnetic field. In the blanket, the kinetic energy of the neutron will be transformed into heat, which will be subsequently converted via a conventional steam cycle into electricity.
Deuterium accounts for about 0.015% of all naturally occurring hydrogen in the oceans on Earth and therefore it is available in almost unlimited quantities. Naturally occurring tritium is extremely rare on Earth. Therefore, tritium should be produced in the reactor blanket, by the reaction of the neutrons with lithium. Lithium is approximately uniformly present in the Earth's crust, the total stock is estimated to be 100 million tons.
Fusion has many advantages, namely a practically limitless fuel supply, no production of long lived radioactive materials, no CO2 emission in reactor operation, and therefore no contribution to climate change. All these features make fusion energy a safe, sustainable and environmentally attractive source of energy for future electricity supply.