How do fusion reactors work?[ Front page ] [ Bibliography ] [ Previous ] [ Next ]Scientists have been trying for many years to build nuclear reactors that would allow a sustained fusion reaction to occur. There are several factors that influence a fusion reaction. Since very high kinetic energies are needed for nuclei to fuse, the plasma in which fusion occurs is extremely hot. Temperatures in excess of 100 million degrees celsius are required for the easiest fusion reaction to take place. Plasmas are fluids, and therefore they have no permanent shape and will quickly disperse if not confined. A 100 million degree plasma will vaporise any container in which it is placed, so magnetic fields are used to contain the plasma. Since the electrons are stripped from the atoms in a plasma, all that remains is the positively charged nucleus, which can be acted on by magnetic fields. In magnetic confinement reactors, so-called magnetic bottles are created with magnetic fields that confine the plasma. In experiments, however, plasmas can only be contained for a few seconds before their oscilations cause them to come into contact with the walls of the reactor. The biggest problem in controlling plasmas with magnetic confinement is their chaotic behaivior. With continuing research, longer containment times are being recorded. Inertial confinement reactors use a different approach. Small fuel pellets containing isotopes of hydrogen, usually deuterium and tritium, are caused to undergo fusion by extremely powerful lasers that can produce up to 2*10^14 Watts for very short periods (Halliday et al, 1112). Nuclear fuel for both types of reactor is almost always deuterium and tritium, hydrogen nuclei with one and two neutrons, respectively. Deuterium can be obtained from common sea water, it is present in about 1 part to 6700 hydrogen atoms in seawater (Halliday, 1110). Tritium is also present in seawater, but only in trace amounts. Tritium can also be obtained from Lithium inside of a nuclear reactor. Once energy has been released by a nuclear fusion reaction, the conversion to electrical or mechanical energy will probably be similar to that used by contemporary devices. The heat from the reaction will be used to heat water which will drive steam turbines, whose mechanical energy can be used directly or more likely converted into electrical energy. |