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The
energy Nuclear |
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The energy nuclear is produced in the fission or the fusion of atomic nuclei.
The possibility to take advantage of the energy nuclear in order to produce to
electric power was prevailed in years Fifty, as a result of the happened one obtained
from the scientists Americans, during the second world war, in the realization
of the powerful bomb To, based on the fission nuclear. The energy amount that
can be gained from the atomic nucleus, in fact, is by far greater of the one which
the combustion is obtained in transformations chemistries which, that they are
involved constituent the elementary ones of the more external part of the atom.
Until 1800 approximately the main fuel it was the wood, that it allowed to indirectly
use the stored solar energy from the trees in the course of their life. With the
advent of the industrial revolution, the man has begun to use fossil fuel, like
the coal and the oil, anch'essi, in last analysis, reservoirs of stored solar
energy in the time. Burning a fossil fuel, as an example the coal, the atoms of
hydrogen and carbon of the coal are arranged with those of oxygen present in the
air, and produce to carbon dioxide and water; in this chemical reaction it comes
produced a heat amount that corresponds to approximately 6500-9500 kcal/kg, equivalent
to 1,6 kilowattora/kg. The typical yield of a chemical reaction is this, that
it derives from transformations of the structure electronic of the atom. A part
of this thermal energy, moreover, comes subsequently absorbed from the same fuel,
in order to maintain it one such temperature to render the prosecuzione of the
reaction possible. Viceversa, in a typical reaction nuclear, which the fission
of the uranio, 1 kg of uranio 235 develops, in heat shape, 18,7 million kilowattora.
The fission
The phenomenon, uncovered in from Or. Hahn and F. Strassmann and independently
from F. Joliot and 1938 L. Meitner and Or. R. Frisch, as a result of work of Firm,
was revealed taking advantage of the neutron action discs of a valve on the uranio.
The lantanio was stated that this element, bombed from neutrons, breaks off and
produces two new elements of intermediate mass, to es. the bromo and. In the single
process of fission of the nucleus of uranio more neutrons are emitted, in average
from 2 to 3 (ready or instantaneous neutrons), and free energy, mostly under shape
of kinetic energy of fission fragments; subsequently the fragments, that they
are in general terms unstable nuclei, decay sometimes emitting of neutrons (neutrons
delay to you). All the nuclei of heavy elements, beginning from the thorium, can
endure the fission with greater or smaller facility, in correspondence of energies
more or less elevated of neutrons incidents. The fission can happen also spontaneously
or can be induced from photons (fast fotofissione) and loaded particles (for es.
protons or particles to). The nuclei of elements uranio 233, uranio 235, plutonio
239 can endure the fission any are the energy of the neutron incident and the
maximum probability that the process is come true has in neutron correspondence
many discs of a valve (thermal neutrons). Viceversa the fission of uranio the
238 happens alone with fast neutrons much. The energy freed in a single process
of fission in uranio the 235 is of approximately 200 MeV. In this case 2,4 neutrons
for nucleus are produced in average that has endured the fission; these neutrons
can be are become lean or can to they time produce to other fissions, giving origin
to chain reaction when the number of a produced is greater of the number of neutrons
is become lean or dispersed neutrons.
The fusion
The fusion process consists in joining between they two or more light nuclei in
order to obtain of one heavier; it is therefore the inverse one of the fission.
In theory for fusion nuclear the approach between they of protons agrees until
the point to make to enter in game the nuclear forces short range. Practically
one finds of forehead to enormous difficulties due to us to the resistance of
the repulsive forces between loaded electrical workers with equal sign. In order
to gain such forces it is necessary to carry the matter to the state of plasma
by means of temperatures made out to ten million degrees. E' clearly that, once
grafted the fusion process, the enormous freed amounts of energy do not have difficulty
to support it, giving to place to fusions on a large scale how much wants. The
fusion processes nuclear give one amount of energy, nuclear energy, ten times
generally advanced to that one freed in the fission processes; here because it
would be preferred to use such process. The sun works this principle second. Every
second, in the Sun, 564,5 tons of Hydrogen come converted in 560 tons of Helium,
while 4,5 tons become energy that, under shape of range beams, will go back slowly
to the surface for being irraggiata in the space and to reach in smallest part
on the Earth. In a gas constituted from heavy isotopes of hydrogen, deuterium
and trizio, every event of fusion rilascia an equal energy to 17,6 MeV, than manifest
at first like kinetic energy of the produced helium nucleus 4 and the neutron,
therefore is transformed in thermal energy, determining an express heating of
the surrounding gas. The gas reagent finds in the state of the said matter plasma,
that mixture of positive and negative free charges consists in one, altogether
neutral. Because the process is favorable is necessary to confine the plasma within
a reduced space, therefore to increase the most possible number of the fusion
events.