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Nuclear energy reactors, the most common
mix is stable uranium (called
reactions, U238) with unstable uranium
Nuclear
unlike chemical reac- (U235), so that the concentra-
tions, take place using tion of the U235 allows
bits (particles) in the control of the disintegration
central part (the reaction.
nucleus) of the atom.
As you will remember This is the basis of present-
from school science day nuclear energy: the
classes, atoms are the controlled disintegration of
n ational electric supply from smallest part of an element, radioactive unstable nuclei
fifty-nine nuclear plants. In
and have a nucleus, the home (radioactive isotopes). In a
the twenty-seven EU coun-
of protons and neutrons (and simplified nuclear power
tries, there are already 152
a bunch of other small, light- plant, the mixture used for
reactors producing 30% of weight particles being disco- fuel rods consists of a fairly
Europe's electricity. In vered by CERN all the time), low concentration (about
Switzerland, there are five
as well as electrons orbiting 3.5%) of U235 mixed into an
reactors generating 40% of
around the outside of the enormous amount of U238.
the national electrical supply; nucleus. There are heavy The disintegration or brea-
in the United States, there are atoms with lots of protons and king up of these heavy nuclei
104 reactors producing nearly neutrons, and lighter ones is called "fission": fission of
20% of all electricity. So with very few. U235 or other radioactive iso-
nuclear energy is real, signifi-
topes (e.g. plutonium 239)
cant -- and most importantly - Fission produces two or more other
- safe and non-polluting. nuclei of lower mass -- and a
I m Safe, I hear you cry, but what Many of the heavy elements very small net loss of mass;

about Chernobyl and what have unstable nuclei, and tend this mass loss is converted to
to disintegrate over time, but energy through Einstein's
about Three Mile Island? And
that "time" can be extremely famous E=mc2 equation. The
what about nuclear waste?
long -- centuries -- or extre- remaining material is a com-
Well, of course, Chernobyl
mely short -- milliseconds. plex mixture of other ele-
was a disastrous accident When they disintegrate, they ments, some of which are
which happened twenty years spin off some of the particles radioactive; this mixture is the
ago, and few people will deny in the nucleus, which someti- infamous nuclear waste,
that it was probably the worst
mes bang into other nuclei which requires processing
industrial accident the world
and cause them to disintegra- and careful disposal.
has ever seen. But no other
te also. If one has a lot of
reactor in the modern world is
these unstable ("radio So, in simple terms: uranium
like Chernobyl -- that type of
0 reactor hasn't been made for -active") nuclei near enough is mined, enriched to bring
to each other such that the dis- the U235 content up to 3.5%
over twenty years and none integrations happen extreme- from the naturally-occurring
will be. It was old-fashioned ly quickly, all hell breaks 0.7%, made into fuel rods
even when it was built! Three
loose and you have a chain which in a reactor generate
Mile Island was an accident
reaction. heat during fission, which
that didn't happen -- but it was
makes steam, which turns tur-
pretty close, and lessons were
So, if you get the right kind of bines and which ultimately
learned. No other significant unstable element with the makes electricity. This is the
accident has occurred with right amount of it present (the commercial process known as
nuclear energy worldwide.
critical mass), you get a nuclear fission energy.
nuclear explosion -- an ato-
One could spend a lot of time
) mic bomb. This is usually not One can see that there is no
discussing these items, but we
a pleasant situation, and carbon dioxide and no other
should move on to the princi-
obviously not a normal one -- greenhouse gases produced in
pal purpose of this article --
bombs aren't going off all the this system for generating
that is, to explain how nuclear
time. The idea is to produce a electricity, but there is nuclear
energy is generated and, in
mixture where the unstable waste; this is probably the
particular, what new types of
nuclei are mixed in with sta- most difficult problem
nuclear energy are foreseen.
ble ones. For nuclear energy nuclear power plants have to
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