The union of light nuclei into heavier
nuclei can also lead to a transfer of mass and a consequent liberation
of energy. This reaction is known as nuclear fusion. Such a reaction
is believed to be the principal source of the sun's energy.
nuclear fusion on the sun
Making Nuclear Fusion
Possible
Fusion of the two deuterium nuclei will
only occur if they overcome their mutual electrostatic repulsion.
This may happen if they collide at very high speed when, for example,
they are raised to a temperature of as high as 100 million oC.
Then, the energy released by fusion will allow the reaction to
continue.
However, how can
we achieve such high temperature?
This reaction can be triggered off with
energy produced from nuclear fission. All matter is gaseous above
about 6000 oC. If we make it even hotter, a [plasma] will
be formed. Since no physical container can withstand such high
temperatures, the most promising method seems to be magnetic confinement
in which the gas is ionised. The gas is placed in a region with
strong [magnetic field] where
the [flux lines] form
circles. Then, the ions will spiral along the flux lines.
Potential of Fusion
Power
Although the fuel for nuclear fission
(U-235 is rare), deuterium and tritium for nuclear fusion is much
more abundant. There are 1025 deuterium atoms in one
cubic metre of water. Tritium, which is produced from lithium,
is also abundant. Therefore, fusion power can satisfy energy needs
for at least 200 times the lifespan of the thermal nuclear reactor
program.
Also, the resulting fusion product, helium, is inert and non-radioactive.
It can be released back into the air afterwards. It is much easier
to handle than the radioactive waste from fission.
Besides using nuclear fusion as a source of energy, this nuclear
process has also been used to produce another lethal weapon, the
hydrogen bomb. Hydrogen fusion bombs are designed to maximize
the production of neutrons. The bomb is detonated at a few hundred
metres above ground; people in the vicinity are killed by the
intense neutron radiation but buildings and vehicles are relatively
unscathed.
A
fusion bomb
But after decades of research, scientists
still have not solved all the technical problems.
The problem of fusion remains a great technical challenge. If
the problems can be solved, mankind will no longer have to worry
about energy shortage.
*back* (C) 1999 ThinkQuest Team 27954