The electric energy from a nuclear source is obtained from the fuel (uranium reaction) reaction heat o used as a basic principle for the operation of a
conventional thermal power plant, which is always the same: the burning of
fuel produces heat, it boils the water of a boiler transforming it in steam.
The steam moves a turbine that in turn, starts a generator that produces electricity.
To understand what is the energy released by a nuclear reaction, it is necessary
to understand a bit more about the atom.
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Atoms are lighter or heavier depending on the number of particles comprising it. The lighter atom known
is the hydrogen atom and the heavier is the uranium atom.
An atom is comprised of a nucleus and smaller particles that gravitate around the nucleus. These particles
are called electrons; they are very light and have a negative electric charge. Inside the nucleus, there are
two types of particles, called protons and neutrons.
The number of protons is always equal to the number of electrons, but their charge is positive. As for the
neutrons, these vary in number and the more numerous the heavier the atom. They have no electric charge;
they are neutral, as the name indicates.
Although we know that atoms form everything existing in nature, we will only study the atoms of the element
called uranium.
In the uranium found in nature, atoms contain in their nucleus 92 protons and 143 neutrons
(whose sum totals 235), atoms with 92 protons and 142 neutrons (234) and others with 92 protons and 146
neutrons (238). As the protons and the electrons have the same number (92), we can say that these atoms
are chemically equivalent and we will call them isotopes of same element, i.e., the uranium.
To differentiate them, we use the chemical symbol of the element and a number, according to the atomic
weight - isotope I-234, isotope U-235 and isotope U-238.
The shock of a free neutron with the isotope U-235 causes the nucleus division of
such isotope into two parts - another two atoms - generating a relatively high release of
energy. This phenomenon is called nuclear fission.
The nuclear fission causes the transformation of matter into energy, through the division of the isotope U-235.
Why the U-235 and not the U-234 or the U-238?
When the U-235 isotope fission occurs, the nucleus is divided into two parts forming two new elements,
and from that 2 or 3 neutrons are released that in turn, may collide with another U-235 nucleus leading
to another fission, new elements are formed, causing a sequence of fissions called nuclear chain reaction.
In nature, only the U-235 is capable to fission and therefore to sustain a chain reaction.
The use and the control of this released energy is carried out inside nuclear reactors, which in the
nuclear power plants have the same role as the boiler in the ordinary thermal plants.
So as to optimize the nuclear reactions, the uranium is enriched before its use in the reactors. This
operation comprises simply the increase of the level of U-235 isotope (the only one that fissions) in
the isotope mixture of the natural uranium (U-234, U-235 and U-238).
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Among the advantages and contributions presented by the use of nuclear energy instead of the conventional
thermal plants we can state that, when used for the production of electric energy, it is a source of energy
that does not emit any gas of greenhouse effect (carbon dioxide, methane, nitrous oxide and others) and no
gas causing acid rain (sulfur dioxide, nitrogen oxides). The nucleus-electric energy does not emit any
carcinogenic, teratogenic, or mutagenic metals (Arsenium, Mercury, Lead, Cadmium, etc.) as do the alternatives
using fossil fuels. The use of nuclear energy does not release gases or particles that cause urban pollution or
reduction of the ozone layer either.
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