MIT Fights for Clean Power With Holy
Grail of Fusion in Reach
In the first part of a week-long series at the breakthrough
university, our resident geek looks down the belly of extreme machines with
forces some 100,000 times stronger than the Earth's—and forecasts the future
of efficient energy.
By Erik Sofge
Published on: February 25, 2008CAMBRIDGE, Mass. — This is what a
fusion lab is supposed to be like. As I walk in, a woman’s voice is on the
speakers, counting down from 10. Banks of chairs face banks of computer
monitors, where data is literally streaming across application windows that
are pulsing, multicolored and reassuringly complex. And at the head of the
control room is a massive projection showing a diagram of the fusion chamber
nearby—a top-down view of the donut-shaped, concrete-lined structure that’s
about to fill with superheated ionized gas, or plasma. On the same wall is
looped footage of the last “shot,” a brief attempt to harness that plasma,
and make fusion a little more feasible. The countdown is over, and there’s a
sound straight out of sci-fi—a high tone coupled with a deep, resonating
hum. On a tiny, black-and-white monitor mounted on the ceiling, a 1-second
flash ripples across the screen. A sign lights up over the door leading to
the chamber, indicating that the oxygen is too low for anyone to approach
without breathing gear, and the clock starts again. Next shot in 15 minutes.
MIT’s Plasma Science and Fusion Center (PSFC) is about as Hollywood-worthy
as science gets. The stakes, after all, could hardly be higher. If fusion
can be perfected, it could mean a golden age for power production, with
systems providing all of the benefits of nuclear reactors—but none of the
drawbacks. Fusion is, to some extent, the exact opposite of fission: Instead
of splitting atoms, fusion combines them, creating larger atoms and
releasing a massive amount of energy in the process. Despite the high
temperatures often associated with plasma, fusion is a relatively stable
reaction, generating little to no radioactive waste. Even in a worst-case
scenario, there’s no chance of a fusion reactor turning into a catastrophe
on the scale of Three-Mile Island or Chernobyl. “Fission can run away,” says
Miklos Porkolab, director of the PSFC. “Fusion can only fizzle.” Since
there’s no chain reaction at work, the biggest danger associated with fusion
is a temperature collapse. And even if the materials lining the chamber were
to suddenly give way because of sabotage or terrorism, the introduction of
debris into the plasma cloud would actually smother the process at an even
faster rate. Fusion is fragile, difficult to maintain and ultimately its own
worst enemy. But it is not dangerous.
That quality makes it utterly useless as a weapon, Porkolab explains, which
is why the federal government decided to declassify its fusion research 50
years ago and make the results public. That was effectively the birth of
open, academic fusion in the United States. So a half-century into this
quest for one of science’s holy grails, are we any closer to grace?
The answer, not surprisingly, is mixed. Here at MIT, the fusion center’s
primary research tool is the Alcator C-MOD, the largest university-run
fusion reactor in the world, and one of only three “tokamaks” in the
country. Tokamaks are reactors that use magnetic fields to control the flow
of plasma. Extreme machines like the C-MOD, which has the most powerful
magnetic fields of any tokamak (and some 100,000 times stronger than the
Earth’s) have enhanced our understanding of fusion. But a truly efficient
reaction, with more energy released than poured in, is still decades away.
The problem, Porkolab says, is turbulence. To increase the chances of a
fusion reaction, a cloud of plasma must be incredibly hot and dense. As the
atoms become more closely packed and excited, the natural tendency for
nuclei to repel each other can be overcome. C-MOD uses microwaves to heat
the ionized gas and magnets to shape it, building up pressure within the
plasma. But as any meteorologist can tell you, juggling temperature and
pressure is a recipe for bad weather. “We have our own storms, inside the
plasma, just like in the atmosphere,” Porkolab says. Temperature gradients
within the plasma can lead to eddies, and the more unstable the cloud
becomes, the more heat it loses. When the temperature gets low enough, the
reaction dies. Plasma turbulence, in other words, is the biggest obstacle to
fusion, limiting current reactors to brief pulses and preventing the kind of
long-term reaction necessary for true power production.
That's why, when the next countdown begins in the control room, and I try to
catch the real-time flash of the plasma shot on that tiny ceiling-mounted
monitor, it’s gone before my camera can even focus. The replay starts to
loop on the main screen—a slightly misleading bit of pyrotechnics, since the
visible light released by the shot is generated at the edges of the plasma
donut, where temperatures are at their lowest, and where fusion is not
likely to occur. And while it’s possible that C-MOD’s pulses could one day
last longer than seconds, this particular tokamak won’t reach the promised
land. In many ways, C-MOD’s most important job is to pave the way for a
reactor 10 times its size, called ITER.
The product of an international collaboration, ITER will be the world’s
largest tokamak, and according to MIT’s Porkolab, it will be capable of
pulses as long as 8 minutes, generating up to 500 megawatts of power (the
most powerful tokamak, Britain’s JET, tops out between 10 and 20 MW). The
jointly developed reactor will have roughly the same shape as C-MOD, but
with 1000 times more volume in its chamber, and radio-frequency arrays
operating at much higher frequencies. The goal for ITER is a self-sustaining
reaction, where the plasma cloud remains stable and intact for long periods.
For that to happen, scientists like Porkolab are using supercomputers to
more precisely model plasma turbulence, and to develop novel methods of
avoiding it. One technique is to go beyond simply surrounding the cloud with
magnetic fields and slice it into cross sections, creating layers that flow
alongside each other, similar to the titanic superheated clouds on Jupiter.
This process can break up the eddies that lead to instabilities and create a
more sustainable environment for fusion.
But even ITER, which is scheduled to be built within 8 to 10 years, is
intended as a research facility—not as an answer to our current energy
dilemma. It might produce an overall surplus of energy, but it won’t be
cost-effective production. For that, Porkolab estimates we’ll have to wait
for ITER to show results, possibly in the 2020s, and then wait another
decade or so while demo reactors are built. That means we’d see economically
feasible fusion power by 2035, at the earliest, and increasingly efficient
commercial reactors somewhere in the middle of the century.
Even that protracted timeline now appears optimistic. Since 2006, when seven
member countries committed to the ITER’s $10 billion budget, federal funding
for scientific research in the United States appears to have bottomed out.
The U.S. agreed to pay 9.1 percent of the project’s total cost—but of the
$160 million contribution planned for this year, Congress has approved just
$10.7 million. Porkolab says eight ITER engineers had been laid off without
severance pay.
The C-MOD reactor is also limited by shrinking science funds. With more
financial support, it could operate for 24 weeks out of the year. “Progress
is very slow. We’re only running about half the time,” Porkolab admits. The
work is likely to slow even further because of nationwide cuts to
high-energy physics programs; such cuts have already led to 200 layoffs at
Fermilab, a Department of Energy-funded particle accelerator in Illinois. If
belts are in need of tightening, it might seem reasonable to limit research
that appears to be wandering on the fringes. But when the primary goal of
fusion is a revolution in clean energy, and the rest of the world is
preparing to take a historic step in that direction, scientists fear it’s a
particularly dangerous time to limit C-MOD and effectively pull out of ITER.
But even if C-MOD never reaches its full research potential, there’s more
than one way to cook a plasma donut, and scientists are also working
feverishly on those. I leave C-MOD’s eerily perfect control room, with its
starship-computer voice and distant, periodic generator rumble, for an
entirely different set of pop-culture associations. Deeper, more
subterranean, is a three-story-tall jumble of stainless steel—a mad
scientist’s vision called the Levitating Dipole eXperiment, or LDX. Through
grates in the floor, I can see researchers in hard hats weaving among the
cables on the level below. In this reactor, the process of fusion
confinement is complicated even further—a superconducting ring is lowered
into the center of the chamber, where it levitates within the plasma. The
resulting magnetic field is closer to the kind of field produced by planets
like Jupiter. This project, which is a collaboration between MIT and
Columbia University, is currently the only fusion experiment in the United
States that uses the same kind of superconducting magnets that ITER will
use. The project achieved a successful levitation this past November;
unfortunately, there will be no levitation today, no plasma ignitions or
ominous countdowns. For the LDX, glimpses of plasma—and the holy grail
within—are few and far between.
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