POWER June 2020 - 36

NUCLEAR TECHNOLOGY
Fusion Energy Is Coming, and
Maybe Sooner Than You Think
The joke about fusion energy is that it's 30 years away and always will be. But
significant recent advances in fusion science and technology could potentially put
the first fusion power on the grid as soon as the 2040s.
Thomas W. Overton, JD
W
hen British physicist
Arthur
Stanley Eddington first proposed
in the 1920s that the
sun and stars were powered by the fusion
of hydrogen into helium, his idea
sparked a rush of research and speculation
into the possibility of bringing
this energy source to earth. It was not
long before journalists and pulp fiction
authors were predicting a time, surely
not far away, when the world would be
powered by simple fusion reactors requiring
nothing more than abundant hydrogen
from water.
Obviously, these early predictions
were more than a little off-base. Vastly
more is understood about the physics
of fusion energy than in Eddington's
day, yet commercial electricity generation
from fusion still remains a goal
rather than a reality. Decades of overly
enthusiastic predictions have led to a
long-running joke that fusion is the energy
source of the future-and always
will be.
Practical, economic generation from
fusion is not yet here, and it's a solid bet
that it will not arrive on the grid before
the 2030s. Yet that reality is considerably
closer than many people realize.
As the result of decades of scientific
advancement by the U.S. and other nations,
most of the key physics questions
behind fusion have been answered.
Meanwhile, the first reactor that should
achieve " burn " -that is, self-sustaining
fusion-is currently under construction
in France, with operations set to begin
within the next few years (Figure 1).
Though it may be premature for utility
resource planners to begin preparing
for electricity from fusion, the time
is growing closer when it becomes an
option alongside other large generation
projects. Accordingly, power generation
professionals can benefit from a clear
understanding of the current fusion
landscape and where things are likely to
go over the next decade.
36
1. The ITER project, shown during construction in February 2020, will be the first experiment
to create a " burning, " or self-sustaining, fusion plasma. This photo shows the partly completed
building that will house the fusion tokamak and its support systems. Courtesy: ITER
The Basics of Fusion
Fusion is a nuclear reaction in which two
or more atomic nuclei combine to form
one or more different atomic nuclei and
often subatomic particles as well. The
fusion of light elements releases energy
due to the interplay of two opposing
forces: the " strong " nuclear force,
which holds protons and neutrons together
in the nucleus, and the Coulomb
force, which causes positively charged
protons to repel each other.
At the very short distance scales of
an atomic nucleus, the strong force
overcomes Coulomb repulsion to bind
the protons and neutrons together.
When small nuclei are fused together,
this increases the strong force nuclear
binding, releasing energy in the form of
radiation and/or emission of subatomic
particles. (Larger nuclei-those above
iron-do not release energy when they
fuse, as the higher number of protons
increases Coulomb repulsion.)
These nuclear binding forces are far
stronger than the forces that hold elecwww.powermag.com
trons
in orbit around a nucleus and influence
the energy of chemical processes.
This is why fusion fuels offer vastly
higher energy density than chemical
methods-about a million times denser
than fossil fuels.
A variety of fusion reactions are possible.
Proton-proton fusion is the process
that powers stars like our sun.
This gravity-powered reaction requires
enormous densities and takes about a
billion years to complete. Thus, it's not
something that would be practical for
energy production on earth. Instead,
terrestrial magnetic fusion experiments
employ lower densities but far higher
temperatures, around 100 million degrees
Celsius. When confined at these
temperatures, the nuclei can collide
with sufficient speed to overcome Coulomb
repulsion and fuse together.
The deuterium-tritium (DT, Figure 2)
reaction is the most useful for fusion
energy because it most easily overcomes
the Coulomb repulsion, and it
has the highest energy release among
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POWER June 2020

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