46
PHYSICS OF THE IMPOSSIBLE
field that confines the plasma inside the doughnut. When an electrical
current is fed inside the doughnut, the gas is heated to stellar temperatures.
The reason scientists are so excited by the ITER is the prospect of
creating a cheap energy source. The fuel supply for fusion reactors is
ordinary seawater, which is rich in hydrogen. At least on paper, fusion
may provide us with an inexhaustible, cheap supply of energy.
So why don't we have fusion reactors now? Why has it taken so
many decades to make progress after the fusion process was mapped
out in the 1950s? The problem has been the fiendish difficulty of compressing the hydrogen fuel in a uniform manner. In stars, gravity compresses hydrogen gas into a perfect sphere, so that gas is heated evenly
and cleanly.
In NIF's laser fusion, the concentric beams of laser light incinerating the surface of the pellet must be perfectly uniform, and it is exceedingly difficult to achieve this uniformity. In magnetic confinement
machines, magnetic fields have both north poles and south poles; as a
result, compressing gas evenly into a sphere is extremely difficult. The
best we can do is to create a doughnut-shape magnetic field. But compressing the gas is like squeezing a balloon. Every time you squeeze
the balloon at one end, air bulges out somewhere else. Squeezing the
balloon evenly in all directions simultaneously is a difficult challenge.
Hot gas usually leaks out of the magnetic bottle, eventually touching
the walls of the reactor and shutting down the fusion process. That is
why it has been so hard to squeeze the hydrogen gas for more than
about one second.
Unlike the current generation of fission nuclear power plants, a fusion reactor will not create large amounts of nuclear waste. (Each traditional fission plant produces 30 tons of extremely high-level nuclear
waste per year. By contrast, the nuclear waste created by a fusion machine would be mainly the radioactive steel left over when the reactor
is finally decommissioned.)
Fusion will not completely solve the Earth's energy crisis anytime
in the near future; Pierre-Gilles de Gennes, French Nobel laureate in
PHYSICS OF THE IMPOSSIBLE
field that confines the plasma inside the doughnut. When an electrical
current is fed inside the doughnut, the gas is heated to stellar temperatures.
The reason scientists are so excited by the ITER is the prospect of
creating a cheap energy source. The fuel supply for fusion reactors is
ordinary seawater, which is rich in hydrogen. At least on paper, fusion
may provide us with an inexhaustible, cheap supply of energy.
So why don't we have fusion reactors now? Why has it taken so
many decades to make progress after the fusion process was mapped
out in the 1950s? The problem has been the fiendish difficulty of compressing the hydrogen fuel in a uniform manner. In stars, gravity compresses hydrogen gas into a perfect sphere, so that gas is heated evenly
and cleanly.
In NIF's laser fusion, the concentric beams of laser light incinerating the surface of the pellet must be perfectly uniform, and it is exceedingly difficult to achieve this uniformity. In magnetic confinement
machines, magnetic fields have both north poles and south poles; as a
result, compressing gas evenly into a sphere is extremely difficult. The
best we can do is to create a doughnut-shape magnetic field. But compressing the gas is like squeezing a balloon. Every time you squeeze
the balloon at one end, air bulges out somewhere else. Squeezing the
balloon evenly in all directions simultaneously is a difficult challenge.
Hot gas usually leaks out of the magnetic bottle, eventually touching
the walls of the reactor and shutting down the fusion process. That is
why it has been so hard to squeeze the hydrogen gas for more than
about one second.
Unlike the current generation of fission nuclear power plants, a fusion reactor will not create large amounts of nuclear waste. (Each traditional fission plant produces 30 tons of extremely high-level nuclear
waste per year. By contrast, the nuclear waste created by a fusion machine would be mainly the radioactive steel left over when the reactor
is finally decommissioned.)
Fusion will not completely solve the Earth's energy crisis anytime
in the near future; Pierre-Gilles de Gennes, French Nobel laureate in