WHAT IS FUSION?
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is the process that powers the sun and the
stars. It is the reaction in which two atoms of hydrogen combine
together, or fuse, to form an atom of helium. In the process
some of the mass of the hydrogen is converted into energy.
The easiest fusion reaction to make happen is combining deuterium
(or heavy hydrogen) with tritium (or heavy-heavy
hydrogen) to make helium and a neutron. Deuterium is
plentifully available in ordinary water. Tritium can be produced
the fusion neutron with the abundant light metal lithium. Thus
fusion has the potential to be an inexhaustible source of energy.
To make fusion happen, the
atoms of hydrogen must be heated to very high temperatures (100
million degrees) so they are ionized (forming a plasma) and have
sufficient energy to fuse, and then be held together i.e. confined,
long enough for fusion to occur. The sun and stars do this by
gravity. More practical approaches on earth are magnetic confinement,
where a strong magnetic field holds the ionized atoms together
while they are heated by microwaves or other energy sources,
and inertial confinement, where a tiny pellet of frozen hydrogen
is compressed and heated by an intense energy beam, such as a
laser, so quickly that fusion occurs before the atoms can fly
Who cares? Scientists have sought to make fusion
work on earth for over 40 years. If we are successful, we will
have an energy source that is inexhaustible. One out of every
6500 atoms of hydrogen in ordinary water is deuterium, giving
a gallon of water the energy content of 300 gallons of gasoline.
In addition, fusion would be environmentally friendly, producing
no combustion products or greenhouse gases. While fusion is a
nuclear process, the products of the fusion reaction (helium
and a neutron) are not radioactive, and with proper design a
fusion power plant would be passively safe, and would produce
no long-lived radioactive waste. Design studies show that electricity
from fusion should be about the same cost as present day sources.
close! While fusion sounds simple, the details
are difficult and exacting. Heating, compressing and confining
hydrogen plasmas at 100 million degrees is a significant challenge.
A lot of science and engineering had to be learned to get fusion
to where we are today. Both magnetic and inertial fusion programs
expect to build their next experiments that will reach ignition
and produce more energy than they consume shortly after the year
2000. If all goes well, commercial application should be possible
by about 2020, providing humankind a safe, clean, inexhaustible
energy source for the future.