Fusion 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 by combining 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 andMagnetic 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 apart.
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 agallon 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.
We’re Getting 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 energysource for the future.
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reaction in which two atoms of hydrogen combine together, or fuse, n
Deuterium P
to form an atom of helium. In the process some of the mass of the
Neutron
n
hydrogen is converted into energy. The easiest fusion reaction to make
Fusion
happen is combining deuterium (or “heavy hydrogen) with tritium (or
“heavy-heavy hydrogen”) to make helium and a neutron. Deuterium is P
n
n P
plentifully available in ordinary water. Tritium can be produced by n
n P
combining the fusion neutron with the abundant light metal lithium.
Helium
Tritium
Thus fusion has the potential to be an inexhaustible source of energy.
To make fusion happen, the atoms of hydrogen must be heated to
n He
very high temperatures (100 million degrees) so they are ionized
(forming a plasma) and have sufficient energy to fuse, and then be held
E=mc2
D T
together i.e. confined,
long enough for fusion
Magnetic
to occur. The sun and
Confinement Magnetic stars do this by gravity.
Field
Nucleus More practical approaches on earth are magnetic
+
confinement, where a strong magnetic field holds the ionized
Intense
atoms together while they are heated by microwaves or other
Energy
-
energy sources, and inertial confinement, where a tiny pellet of
Beams
Electron
frozen hydrogen is compressed and heated by an intense energy
Fuel
beam, such as a laser, so quickly that fusion occurs before the
Pellet
atoms can fly apart.
Sun
Who cares? Scientists have sought to make fusion work on
Inertial
Confinement earth for over 40 years. If we are successful, we will have an
Gravitational
Confinement 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 Fusion
studies show that electricity from fusion should Power
Power
ITER
be about the same cost as present day sources. 1,000
Plant
MWth 100 TFTR/JET
TFTR
10
We’re getting close! While fusion sounds JET
1,000
simple, the details are difficult and exacting. JET/TFTR
kWth 100 JT–60U
TFTR
Heating, compressing and confining hydrogen 10
House
DIII–D
plasmas at 100 million degrees is a significant PDX
1,000 DIII Achieved (DD)
PLT
challenge. A lot of science and engineering 100 Achieved (DT) Light
Alcator C
Wth 10 Projected (DT) Bulb
had to be learned to get fusion to where we are
1
today. Both magnetic and inertial fusion pro- 1970 1980 1990 2000 2010
grams expect to build their next experiments Alcator C: Massachusetts Institute JET: Joint European Torus
that will reach ignition and produce more energy of Technology
JT–60U: Japanese Tokamak Experiment
than they consume shortly after the year 2000. DIII & DIII–D: General Atomics
TFTR: Princeton Plasma Physics Laboratory
Tokamak Experiment
If all goes well, commercial application should PDX: Princeton Divertor Project
ITER: International Thermonuclear
be possible by about 2020, providing Experiment Reactor PLT: Princeton Large Tokamak
humankind a safe, clean, inexhaustible energy
source for the future.
very nice