Nuclear fusion


Nuclear Fusion
 
 
What is fusion?
Fusion is the process that powers the sun and other stars. It is the reaction in which two light atoms, such as atoms of hydrogen, combine or fuse to form a heavier atom, such as an atom of helium.  In the process, some of the mass of the hydrogen is converted into energy.  Hydrogen atoms repel each other due to the electrical charge of their core or nucleus.  For fusion to occur, the atoms of hydrogen must be heated to extremely high temperatures (millions of degrees C) so they have enough thermal energy to overcome this repulsion, and then they must be held together or confined long enough for fusion to occur. The sun and stars are held together by gravity, but this method only works when the amount of fuel is much larger than the earth.  Two alternative methods are being studied to produce controlled fusion on earth. With magnetic confinement fusion, strong magnetic fields hold the electrically charged or ionized atoms together as they are heated.  With inertial confinement fusion (ICF), the method discussed here, a tiny pellet of frozen hydrogen is compressed and heated so quickly that fusion occurs before the atoms can fly apart, so the reaction is confined, in effect, by the inertia of the fuel.
 
Why is fusion power attractive?

Controlled fusion has the potential of becoming an important energy source because the fuel is widely available and because the reaction is relatively clean. the easiest fusion reaction to produce is combining two forms orisotopes of hydrogen, deuterium (also called heavy hydrogen) and a heavier isotope tritium, to make helium and a neutron. Deuterium is found abundantly in ordinary water, and tritium can be produced by combining the fusion neutron with the light metal lithium.  There is enough deuterium in the oceans to provide an effectively unlimited supply of energy.

Compared with the main sources of electrical energy used now, fusion is a clean source of energy.  Unlike the burning of fossil fuels, like coal and petroleum, fusion  produces no "greenhouse" gases and therefore does not contribute to global warming.  Also, even though fusion is a nuclear process, it produces no long-lived radioactive waste.  A properly designed fusion power plant would therefore be safe, and design studies indicate that electricity from such a plant would cost about the same as today.