| MadSci Network: Physics |
Hi Jeremy.
You asked is Neutron fusion feasible or practical.
There are many different nuclear fusion reactions occurring in the sun
and other stars, but only a few such reactions are of practical value for
potential energy production on earth.
The easiest fusion reaction to make happen is combining deuterium with
tritium to make helium and a neutron.
Deuterium is plentifully available in ordinary water.
Tritium can be produced by combining the fusion neutron with the abundant
light metal lithium.
The "D-T" reaction has the highest reaction rate at the plasma
temperatures which are currently achievable; it also has a very high
energy release.
These properties make it the easiest reaction to use in a man-made fusion
reactor.
The proton-proton chain, the reaction process is the dominant fusion
mechanism in light stars, including our sun. In the P-P chain, two pairs
of protons fuse, forming two deuterons.
Each deuteron fuses with an additional proton to form helium-3.
The helium-3 nuclei then fuse to create beryllium-6, which is unstable
and disintegrates into two protons plus a helium-4 (alpha particle).
In addition, the process releases two neutrinos, two positrons, and gamma
rays. The positrons annihilate quickly with electrons in the plasma,
releasing additional energy in the form of gamma rays.
The neutrinos interact so weakly that they fly right out of the sun
immediately.
The p + p => D reaction rate coefficient in the sun is much lower than
that achievable with a deuterium-tritium fuel mix. A proton in the sun
will exist for an average of billions of years before it fuses.
By comparison, a deuteron in a magnetic fusion power plant would only
exist for about 100 seconds, and a deuteron in an imploding, fully-burned
inertial confinement pellet only for 1.0E-9 seconds.
Neutron – Neutron fusion dose not appear to be feasible at any time in
the near future. Though it is theoretically possible in the laboratory
the main problem is that it suffers from an unattractive power balance it
consumes significantly more power than it produces. So for now magnetic
fusion research has focused on systems that produce a high fusion gain,
producing more power than they consume.
The difficulty in producing fusion energy has been to develop a device
which can heat the deuterium-tritium fuel to a sufficiently high
temperature and then confine it for a long enough time so that more
energy is released through fusion reactions than is used for heating.
I hope this answers your question.
Sources: http://FusEdWeb.llnl.gov/CPEP/
http://w
ww.pppl.gov/fusion_basics/pages/fusion_basics.html
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