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ARRoGANT CoURiERS WiTH ESSaYS
Grade Level: Type of Work Subject/Topic is on:
[ ]6-8 [ ]Class Notes [Essay on Fusion Energy ]
[x]9-10 [ ]Cliff Notes [ ]
[ ]11-12 [x]Essay/Report [ ]
[ ]College [ ]Misc [ ]
Dizzed: 11/94 # of Words:868 School: ? State: ?
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A fusion reaction is one in which two atomic nuclei merge to form a
heavier nucleus. this is the process that happens in in the stars. In
average stars, like the sun, the process of fusion is converting hydrogen
nuclei (or protons) into helium nuclei. There is an enormous amount of
kinetic energy and gamma rays released in this process that heat the star's
interior, and this realease is what maintains it at the extreamly high
temperatures (greater than 10 million K) required to continue the fusion.
This process has been making the stars go for billions of years has
clear potential as a power source on earth. Once we have started the
reaction, Fusion requires no energy and realeases energy in a great
surplus. It also has no environmental problems and causes no pollutions
whatsoever.
The problems with fusion are the molecules of hydrogen that are
supposed to be fused, electro-statically repel each other at a great force.
The only way to create the conditions where the it is possible to force
these atoms together and override their repulsion is through enormous heat,
this method is called thermonuclear.
Even though fusion reasearch still needs a lot of time, there has been
some progress in discovering how we can use this. The two fusion reactions
that are the most promising both involve the heavier isotopes of hydrogen:
1) deuterium (composed of one proton and one neutron) Deuterium occurs
naturally as a minor constituent in all hydrogen-containing materials--such
as water--in quantities sufficient to meet all the energy needs of
societies for many billions of years.
2) tritium (composed of one proton and two neutrons). Tritium can be
bred from lithium by a neutron-induced reaction in a blanket that could
conceivably surround a fusion reactor. The western United States contains
large lithium deposits in the salts of dry lake beds, and much larger
quantities are dissolved in the sea.
Scientists are trying different combonations of these nuecli to make
fusion. The reaction that occurs with the greatest probability and at the
lowest temperatures involves the fusing of a deuterium nucleus with a
tritium nucleus to form a helium (He4) nucleus and a neutron. The products
contain 17.6 million electron volts of released kinetic energy, this is
great--except it's only in theory.
Now the only thing to figure out is how can someone can get the
deuterium nuecleus and the tritium nuecleus to fuse. The other objective
is to create an energy source that you can get more energy out of than you
put into.
The first method tried was to use a charged particle accelerator to
bombard a solid or gaseous tritium target with energetic deuterium nuclei.
This technique consumes power rather than producing it, however, because
most of the accelerated nuclei lose their enegy traveling like this.
Another idea proposed in 1990 involved Tritium within metal bars that
was put into a tank of dueterium in water. When energy was put into this
tank something in the tritium bars forced dueterium out of the water and a
chemical reaction fused the materials. Unfortunaltely, the was again a net
energy loss, and only a small amount of extra heat was produced.
Another approach to fusion, pursued since about 1974, is
termedinertial confinement. Its aim is to compress a solid pellet of
frozen deuterium and tritium to very high temperatures and densities in a
process analogous to what occurs in a thermonuclear (hydrogen) bomb. The
compression is accomplished by bombarding the pellet from all sides,
simultaneously, with an intense pulse of LASER light, ions, or electrons.
In 1988 it was learned that the U.S. government, which secretly had been
using underground nuclear tests in Nevada to study inertial -confinement
fusion, had achieved such fusion in 1986 by this means, unfortunately it
only lasted less than a second.
After trying these methods, most scientists now agree that the only
way there is a net energy gain obtained is by mimicking the Sun, and
producing starlike thermonuclear conditions.
The goal of fusion--in effect, to make and hold a small star--is so
daunting as to be widely considered the supreme technological challenge yet
undertaken.
In addition to an almost inexhaustible fuel supply, fusion has other
attractive features:
it is environmentally benign; the resulting ash is harmless helium and
hydrogen; and the afterheat in the reactor structure would be much less
than in a fission reactor and would be distributed through a greater
thermal mass. In addition, because fusion is not a chain reaction, it
cannot run out of control, and any tampering to the process would cause the
plasma (the energy involved in the process) to extinguish itself. It would
also be far more difficult to produce nuclear-weapons materials
surreptitiously at a fusion plant than at a fission plant; because no
fissionable material should ordinarily be present at a fusion plant.
Present levels of support for research are aimed at building the first
demonstration fusion plant in about the year 2024. This year is based on
the amount nessesary for fusion reasearch and the very small amount of
money given to fusion to this reasearch by most governments. If spending
increases this year will most likely move out of our life times.