Okay, show of hands. Who wants a nuclear power plant built in his/her
backyard? Anyone? Wouldn't it be neat to be that close to that awesome
power of the atom? Well, most people would shy away from a nuclear
reactor, so let's give a little summary of what a nuclear reactor is all
about.
You may not think so, but energy is actually locked in the nuclei of
atoms.
The nuclei of atoms contain two kinds of particles--protons and
neutrons. The nuclear particles can store energy. Some nuclei
spontaneously rearrange, or lose some particles, and emit energy.
This process is called radioactivity. For example, a radium nucleus
can spontaneously eject a cluster of two neutrons and two protons
(called an alpha particle) and a gamma ray (electromagnetic radiation).
These carry away energy from the nucleus, which changes into a
smaller, more stable form.
Two techniques exist by which nuclear energy is released by
human intervention. The first makes use of elements with very
heavy atoms, such as uranium. More energy is required to hold
together the uranium nucleus than to hold together two nuclei
that are half the size of a uranium nucleus.
In atom bombs and in fission reactors, free neutrons bombard
uranium atoms. When a neutron hits a nucleus, the nucleus splits
into two smaller nuclei, releasing a great deal of energy. In
the reaction, some of the neutrons of the uranium nucleus fly
off and hit other nuclei, causing them to split in two and release
more energy and more neutrons. The process can continue explosively
unless metal rods are inserted in the middle of the uranium to
capture some of the neutrons and slow down the reaction. This
sort of reaction is called a fission reaction because in it nuclei
are broken apart.
The second kind of nuclear reaction is harder to produce and
control. It makes use of the fact that very small nuclei, such
as hydrogen and its isotopes, require slightly more energy per
proton and neutron to exist than do somewhat heavier nuclei. (The
situation is exactly opposite to that of the uranium nucleus,
where the lighter nuclei require less energy.) If two hydrogen
nuclei can be combined to form one heavier nucleus, energy is
released. This type of reaction goes on in the sun. By a somewhat
complicated series of reactions, four hydrogen nuclei join together
to form a new helium nucleus, giving off a great deal of energy
in the process. This is the source of all the energy given offby
the sun.
Temperatures in this kind of reaction must be very high (in
millions of degrees) before the nuclei have enough energy
to collide with the force needed for them to join together. The
reaction is called a thermonuclear fusion reaction. "Thermonuclear"
refers to the heat required for the nuclei to react, and "fusion"
means that in the reaction nuclei join together.
A thermonuclear fusion reaction occurs when a hydrogen bomb
explodes. Scientists are trying to develop a way of releasing
energy by fusion reactions under controlled conditions.
