Home' Technology Review : September 2005 Contents 43
By Invitation Ian H. Hutchinson
T the Interna-
tional Thermonuclear Ex-
perimental Reactor (ITER)
has nally been chosen:
southern France. Both the
European Union and Japan were bidding
to host ITER, and the selection of one of
them opens the way to the scienti c dem-
onstration of controlled fusion energy
production and removes perhaps the last
major impediment to a project under
consideration for nearly 20 years.
This result is good news for the two
bidders, for the rest of the ITER consor-
tium (the United States, Russia, China,
and South Korea), and for the citizens of
the world, since it enables us to take the
next step toward developing a sustainable
energy source---nuclear fusion, the pro-
cess that powers the sun---that produces
zero climate-changing emissions.
Nuclear reactions that release energy
by combining light nuclei like hydrogen's
to form heavier nuclei such as helium's are
called fusion. They are, in a sense, the op-
posite of the ssion reactions that generate
power in present-day nuclear plants. Fis-
sion breaks up the nuclei of heavy elements
such as uranium. Fusion has the potential
to provide practically inexhaustible energy
with greatly reduced radioactive waste.
The fuel in a fusion reaction must
be subjected to tremendous heat, which
tur ns it into an electrically conducting gas
called a plasma. The plasma state must be
maintained long enough for the reactions
to occur. In stars like our sun, gravity con-
nes the plasma in a wonderfully stable
and long-lived con guration. A human-
scale fusion reactor must use a much
stronger con ning force: a magnetic eld.
ITER will use a donut-shaped magnetic
containment device called a tokamak.
But con ning a plasma tightly enough
to enable useful energy release is far more
di cult than early researchers had hoped.
Many important optimizations have been
developed, but one unavoidable measure
is to make the plasma large. Existing large
tokamaks typically have a plasma radius
of three meters and have demonstrated
substantial energy releases. But keeping
their fuel in a plasma state has required
The next big step is to create a plasma
that keeps itself hot with its own fusion
reactions. The ITER collaboration has
designed a reactor that should sustain
such a "burning plasma." It will require a
plasma about twice as large as those pro-
duced by current tokamaks and supercon-
ducting magnets that consume negligible
electric power. ITER will cost about $5
billion to construct.
Fusion is the kind of grand technologi-
cal challenge that calls for international
coöperation. But the length of time its de-
velopment will require can breed skepti-
cism and discourage policymakers. In the
mid-1990s, cuts in the United States' fu-
sion research budget led it to pull out from
the ITER consortium. Thankfully, it re-
joined in 2003, but in a more junior role,
re ecting its relatively modest funding of
fusion projects: $290 million in 2006, less
than half Europe's commitment.
The United States still has two world-
renowned tokamaks---one at MIT, the
other at General Atomics in San Diego---
whose research will be crucial in helping
to resolve and prepare for challenges that
ITER faces. But U.S. leadership in fusion
plasma science cannot be sustained with-
out a renewed commitment of resources.
The United States' present 10 percent
share of ITER will call for peak expendi-
tures of perhaps $150 million per year---
mostly for industrial procurements, not
If that money were taken from the ex-
isting federal fusion research budget, it
would decimate U.S. fusion research.
That is why the U.S. fusion community's
over whelming enthusiasm for ITER is
predicated on strong domestic support for
fusion and plasma physics research, plus
additional funds for ITER construction.
Even if the U.S. increased its funding for
fusion research to $500 million per year,
that would still be substantially less than it
spends separately on high-energy physics,
fossil energy research, and basic energy
sciences, not to mention the recent bud-
gets of the Missile Defense Agency ($9
billion) and NASA ($16 billion).
Ultimately, fusion could prove to be
one of the most environmentally attractive
energy options. The United States should
seize the opportunity to play a strong role
in ITER's success and demonstrate its
commitment and long-term vision as a
scienti c collaborator by revitalizing its
overall fusion program. ■
What about the U.S.?
Fusion, though long-term, is a worthy investment.
Ian H. Hutchinson is head of the
Department of Nuclear Science and
Engineering at MIT. He and his team
designed and built a major national fusion
research facility, which he directed for its
first 10 years of operation.
Fusion's grand challenge requires global
coöperation---and U.S. research funding.
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