What makes Nuclear Fusion possible?
(Lansing State Journal, December 11, 1991)

Fusion is a type of nuclear reaction in which two light nuclei are forced to combine to form a heavier nucleus.  Because the mass of the final nucleus may be less than the sum of the masses of the starting nuclei, excess mass is converted into energy, in accordance with Einstein’s famous formula, E=mc².  The energy is released in various forms: for example, the energy we receive from the sun is a result of fusion.

Since the amount of energy released in a fusion reaction can be large, controlled fusion is a potential source of energy for human use.
Such an energy source is particularly attractive because it is clean burning, meaning the products of the reaction are not environmentally dangerous.

When we look at the waste products of present day energy sources - such as coal or oil - we find gases which produce health and environmental hazards and, in the case of nuclear fission reactors, radioactive waste.

The products of fusion reactions would be stable, easily disposable elements like helium. The potential of such a fuel source has inspired a great deal of research into producing sustainable fusion reactions.

The major difficulty in making a fusion reactor is that, for a fusion reactor to occur, the two initial nuclei must each have a large energy.

Imagine two cars crashing together; if the cars have a relatively low energy - meaning they are not traveling at great speeds - they will collide and bounce off each other.  The cars would have to travel very fast to stick together after the collision.

We can use particle accelerators to give the initial nuclei the required energy, but the nuclei must be accelerated to get one fusion reaction.  The undesirable result is more energy is required to run the particle accelerator than is generated by the fusion reaction.

A large part of this problem is due to high temperatures - millions of degrees - necessary for a fusion reactions.

Recently, a group of scientists at the Joint European Torus (JET) laboratory in England produced 1.7 million watts of power in a fusion reaction which lasted less than one second.  Although the experiment generated a large amount of power, almost ten times as much power was needed to heat the plasma.

Science Theatre thanks Steve Snyder for contributing to this column.

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