For the past 20 years, MIT's Plasma Science and Fusion Center
(PSFC) has been experimenting with nuclear fusion through the world's
smallest tokamak-type (doughnut-shaped) nuclear fusion device -- the Alcator C-Mod.
The
goal? To produce the world's smallest fusion reactor -- one that
crushes a doughnut-shaped fusion reaction into a 3.3 meter radius --
three of which could power a city the size of Boston.
And MIT researchers are getting close to their goal, despite a recent cut in federal funding that could slow their progress.
The
lessons already learned from MIT's smaller Alcator C-Mod fusion device
have enabled researchers, including MIT Ph.D candidate Brandon Sorbom
and PSFC Director Dennis Whyte, to develop the conceptual ARC
(affordable, robust, compact) reactor.
"We wanted to produce something that could produce power, but be as small as possible," Sorbom said.
A
working ARC fusion reactor would use 50 megawatts (MW) of power to
produce 500MW of fusion power, 200MW of which could be delivered to the
grid. That's enough to provide 200,000 homes with electricity.
MIT
A look inside MIT's C-Mod, which is only 0.68 meters in radius
the
smallest fusion reactor with the strongest magnetic field
in the world.
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rather than present a long list of job Read Now
While three other fusion devices roughly the same size as the
ARC have been built over the past 35 years, they didn't produce anywhere
near its power. What sets MIT's reactor apart is its superconductor
technology, which would enable it to create 50 times the power it
actually draws. (MIT's PSFC last year published a paper on the prototype ARC reactor in the peer reviewed journal ScienceDirect.)
The
ARC reactor's powerful magnets are modular, meaning they can be easily
removed and the central vacuum vessel in which the fusion reaction
occurs can be replaced quickly; besides allowing upgrades, a removable
vessel means a single device could be used to test many vacuum vessel
designs.
Fusion
reactors work by super heating hydrogen gas in a vacuum, the fusing of
hydrogen atoms form helium. Just as with splitting atoms in today's
fission nuclear reactors, fusion releases energy. The challenge with
fusion has been confining the plasma (electrically charged gas) while
heating it with microwaves to temperatures hotter than the Sun.
Sustainable energy
The
result of successfully building an ARC reactor would be a plentiful
source of clean and reliable power, because the needed fuel -- hydrogen
isotopes -- is in unlimited supply on Earth.
"What we've done is
establish the scientific basis...for, in fact, showing there's a viable
pathway forward in the science of the containment of this plasma to make
net fusion energy -- eventually," Whyte said.
Fusion research
today is at the threshold of exploring "burning plasma," through which
the heat from the fusion reaction is confined within the plasma
efficiently enough for the reaction to be sustained for long periods of
time.
MIT
A look at the exterior of MIT's C-Mod nuclear fusion device. The C-Mod project has paved the way for a conceptual ARC reactor. Normally, gas such as hydrogen is made up of neutral molecules
bouncing around. When you superheat a gas, however, the electrons
separate from the nuclei creating a soup of charged particles rattling
around at high speeds. A magnetic field can then press those charged
particles into a condensed shape, forcing them to fused together.
The
40-year conundrum of fusion power is that no one has been able to
create a fusion reactor that puts out more power than is required to
operate it. In other words, more power is required to keep the plasma
hot and generating fusion power than the fusion power it produces.
Europe's working tokamak reactor named JET, holds the world's record for power creation; it generates 16MW of fusion power but requires 24MW of electricity to operate.
MIT's
researchers, however, believe they have the answer to the net power
problem and it'll be available in a relatively tiny package compared to
today's nuclear fission power plants. By making the reactor smaller, it
also makes it less expensive to build. Additionally, the ARC would be
modular, allowing its many parts to be removed for repairs to upgrades,
something not previously achieved.
What sets MIT's fusion device apart
What
MIT alone has done is create the world's strongest magnetic containment
field for a reactor its size. The higher the magnetic field, the
greater the fusion reaction and the greater the power produced.
"We're
highly confident that we will be able to show this medium can make more
fusion power than it takes to keep it hot," Whyte said.
MIT Plasma Science and Fusion Center
A cutaway view of the proposed ARC reactor. Thanks to powerful new
magnet technology, the much smaller, less-expensive ARC reactor would
deliver the same power output as a much larger reactor.
Fusion reactors would have several advantages over today's
fission nuclear reactors. For one, fusion reactors would produce little
radioactive waste. Fusion reactors produce what are called "activation
products" with the fusion neutrons.
The small amount of
radioactive isotopes produced are short lived, with a half life lasting
tens of years vs. thousands of years from fission waste products, Sorbom
said.
The reactors would also use less energy to operate than fission reactors.
While
MIT's current Alcator C-Mod produces no electricity, it demonstrates
the effects of a magnetic containment field on super-heated plasma, and
by hot we're talking about 100 million degrees Fahrenheit. By
comparison, our Sun is a chilly 27 million degrees Fahrenheit.
Far
from being dangerous, the 100-million-degree plasma instantly cools and
resumes a gaseous state when it touches the inner sides of the reactor.
That's why a powerful magnetic containment field is needed.
Just
like a fission nuclear reactor, a fusion reactor would essentially be a
steam engine. The heat from the controlled fusion reaction is used to
turn a steam turbine that, in turn, drives electrical generators.
MIT's
current C-Mod fusion device uses plentiful deuterium as its plasma
fuel. Deuterium is a hydrogen isotope that is not radioactive and can be
extracted from seawater.
In order to create a conceptual ARC
reactor, however, a second hydrogen isotope is needed: tritium. That's
because the rate at which deuterium-deuterium isotopes fuse is about 200
times less than the rate at which deuterium-tritium isotopes fuse.
Tritium,
while radioactive, only has a half-life of about 10 years. Although
tritium does not occur naturally, it can be created by bombarding
lithium with neutrons. As a result, it can be easily produced as a
sustainable source of fuel.
With fusion reactors, smaller is better
While MIT's reactor might not fit conveniently into Tony Stark's chest (that is
a movie after all), it would be the smallest fusion reactor with the
most powerful magnetic containment chamber on earth. It would produce
the power of eight Teslas or about two MRI machines.
By
comparison, in southern France, seven nations (including the U.S.) have
collaborated to build the world's largest fusion reactor, the International Thermonuclear Experimental Reactor (ITER) Tokamak. The ITER fusion chamber has a fusion radius of 6.5 meters and its superconducting magnets would produce 11.8 Teslas of force.
However,
the ITER reactor is about twice the size of ARC and weighs 3,400 tons
-- 16 times as heavy as any previously manufactured fusion vessel. The
D-shaped reactor will be between 11 meters and 17 meters in size and
have a tokamak plasma radius of 6.2 meters, almost twice the ARC's
3.3-meter-radius.
The concept for the ITER project began in 1985,
and construction began in 2013. It has an estimated price tag of between
$14 billion and $20 billion. Whyte, however, believes ITER will end up
being vastly more expensive, $40 billion to $50 billion, based on "the
fact that the U.S. contribution" is $4 billion to $5 billion, "and we
are 9% partners."
Additionally, ITER's timetable for completion is 2020, with full deuterium-tritium fusion experiments starting in 2027.
When
completed, ITER is expected to be the first fusion reactor to generate
net power, but that power will not produce electricity; it will simply
prepare the way for a reactor that can.
MIT's ARC reactor is
projected to cost $4 billion to $5 billion dollars and could be
completed in a four to five years, Sorbom said.
The reason ARC
could be completed sooner and at one-tenth the cost of ITER is due to
its size and the use of the new high-field superconductors that operate
at higher temperatures than typical superconductors.
Typically,
fusion reactors use low-temperature super conductors as magnetic coils.
The coils must cooled to about 4 degrees Kelvin, or minus 452 degrees
Fahrenheit, to function. MIT's tokamak fusion device uses a
"high-temperature" rare-earth barium copper oxide (REBCO)
superconducting tape for its magnetic coils, which is far less expensive
and efficient. Of course, "high temperature" is relative: the REBCO
coils operate at 100 degrees Kelvin, or about minus 280 degrees
Fahrenheit, but that's warm enough to use abundant liquid nitrogen as a
cooling agent.
Lucas Mearian
In his left hand, Brandon Sorbom holds a rare-earth barium copper
oxide (REBCO) superconducting tape used in the fusion reactor's magnetic
coils. In his right hand is a typical copper electrical cable. The use
of the new super conducting tape lowers costs and enables MIT to use
plentiful liquid nitrogen as a cooling agent. "The enabling technology to be able to shrink
the fusion device size is this new superconducting technology," Sorbom
said. "While the [REBCO] superconductors have been around since the late
1980s in labs, in the last five years or so companies have been
commercializing this stuff into tapes for large scale projects like
this."
In addition to size and cost, REBCO tape is also able to
increase fusion power 10-fold compared to standard superconducting
technology.
Before MIT's ARC can be built, however, researchers
must first prove they can sustain a fusion reaction. Currently, MIT's
C-Mod reactor runs only a few seconds each time it's fired up. In fact,
it requires so much power, that MIT must use a buffer transformer in
order store enough electricity to run it without browning out the city
of Cambridge. And, with a plasma radius of just 0.68 meter, C-Mod has is
far smaller than even the ARC reactor would
So before it builds the ARC reactor, MIT's next fusion device -- the Advanced Divertor and RF tokamak eXperiment (ADX) -- will test various means to effectively handle the Sun-like temperatures without degrading the plasma performance.
After
achieving sustainable performance, the ARC will determine whether net
power generation is possible. The last hurdle before fusion reactors can
supply power to the grid is transferring the heat to a generator.
IPP, Wolfgang Filser
A researcher works inside of the Wendelstein 7-X (W7-X) an
experimental nuclear fusion reactor built in Greifswald, Germany, by the
Max-Planck-Institut für Plasmaphysik (IPP). The reactor, completed in
October 2015, is the largest to date. Throwing a wrench into its efforts, MIT learned
earlier this year that funding for its fusion reactor under the
Department of Energy (DOE) is coming to an end. The decision to shut
down Alcator C-Mod was driven by budget constraints, according to Edmund
Synakowski, associate director of science for Fusion Energy Sciences
(FES) at the DOE.
In the current budget, Congress has provided $18
million for MIT's C-Mod, which will support at least five weeks of
operations in its final year and cover the costs associated with the
shutdown of the facility, Synakowski said in an email reply to Computerworld. (Researchers hope to find other funding sources to make up for the loss.)
The
PSFC has about 50 Ph.D students working to develop fusion energy. Past
students have left MIT to start their own companies or take develop
academic projects outside of MIT.
Making sure that scientists and
students at MIT can transition into collaborations at other DOE-funded
fusion energy research facilities in the U.S. -- especially the two
primary facilities: DIII-D at General Atomics in San Diego, and NSTX-U
at Princeton Plasma Physics Laboratory -- has been "one of the major
concerns," Synakowski said.
Over the past fiscal year, FES worked
with MIT to establish a new five-year cooperative agreement, beginning
on Sept. 1, 2015, to enable its scientists to transition to FES-funded
collaborations.
Whyte, however, believes the promise of fusion energy is too important for research to wind down.
"Fusion
is too important to have only one pathway to it," Whyte said. "My motto
is smaller and sooner. If we can [create] the technology that allows us
to access smaller devices and build a variety of them..., then this
allows us to get to a place where we've got more options on the table to
develop fusion on a faster timescale."
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And, Whyte said, the scientific basis for small fusion reactors has been established at MIT.
"We
did that despite the fact that we have the smallest of the major
experiments around the world. We actually have the record for achieving
pressure of this plasma. Pressure is one of the fundamental bars you
have to get over," Whyte said. "We're very excited about this."
Plans left over from an unfinished Cold War tech rivalry could help meet the world’s clean energy needs.
Today, the Max Planck Institute in Greifswald, Germany, started up a
nuclear fusion reactor using hydrogen fuel, the Associated Press
reports. German Chancellor Angela Merkel, herself a former physicist,
ceremoniously pushed the button. But the basic design of the new reactor
is as old as the color TV.
Photo of the plasma generated today in the Wendelstein 7-X.
Scientists have struggled to build a bug-free fusion reactor since
the 1950s. The original Soviet model, a bagel-shaped device called a
tokamak, is relatively simple to build and is the same design that
underpins the massive ITER reactor under construction in France. Using
powerful magnetic fields, the machine superheats hydrogen gas until it
becomes plasma. At this point, the hydrogen atoms begin fusing into
helium.
Not to be outdone by the Soviets, the Americans had their own fusion
research program. Lyman Spitzer of Princeton University designed the
American alternative in 1951. Dubbed the stellarator, the extra magnetic
coils that wind their way around the outside of the tube to keep the
plasma fuel under better control, but they make for a much more
complicated design.
So far, both models have had problems. For tokamaks, the plasma
current tends to halt unexpectedly, causing powerful electric fields to
escape and damage the reactor, and for stellerators, construction costs
have kept most on the drawing board. But the Planck Institute is giving
the stellarator blueprint another shot.
The Institute’s reactor, called the Wendelstein 7-X, has been under
construction since 1993—it was “hell on Earth” to build, the project’s
leader told
Science. The first test run was completed in December using helium
fuel, which is easier to heat than hydrogen, the standard fuel. At
today’s event, the Associated Press spoke to physics professor David Anderson of the University of Wisconsin, who was optimistic about that first test:
“The impressive results obtained in the startup of the
machine were remarkable,” he said. “This is usually a difficult and
arduous process. The speed with which W7-X became operational is a
testament to the care and quality of the fabrication of the device and
makes a very positive statement about the stellarator concept itself.
W7-X is a truly remarkable achievement and the worldwide fusion
community looks forward to many exciting results.”
Today’s test smashed hydrogen atoms together to produce superheated
plasma—but only for a fraction of a second. The Wendelstein 7-X isn’t
set up to provide power to northeastern Germany—it’s just testing the
design for future reactors. It could be decades before stellarators
replace other power sources.
Germany just turned on a new experimental fusion reactor
Today, scientists began the first tests of an ambitious new fusion reactor in Greifswald, Germany. Dubbed W7-X, the new reactor is based on the Stellerator design,
in contrast to the Tokamak reactors that dominate much fusion research.
It's still unclear whether the new design will have an advantage in
producing a workable fusion reaction, but the W7-X represents a major
step forward in researching that question. The experiment conducted
today was relatively simple, heating hydrogen particles into a suspended
plasma state, but it represents a crucial first step in the facility's
ambitious research plans.
German
Chancellor Angela Merkel pressed the button to initiate the symbolic
first test. "As an industrial nation we want to show that an affordable,
safe, reliable and sustainable power supply is possible, without any
loss of economic competitiveness," Merkel said in a statement to the
press. "The advantages of fusion energy are obvious."
Following the first successful test of the Wendelstein X-7 Stellarator—extremely sophisticated nuclear reactor in Germany—the Chinese have accomplished a wildly impressive in one of their reactors. According to the South China Morning Post,
China's Experimental Advanced Superconducting Tokamak (EAST) was able
to sustain 90 million Fahrenheit plasma (50 million Kelvin) for 102
seconds. For context, the center of the sun is thought to be only about a
third as hot.
Unlike
the mind-bendingly complex supercomputer-optimized shape of the X-7
Stellerator, China's EAST is torus-shaped, like a donut, and uses
magnetic field to keep its plasma fields in check. At a glance, the most
jaw-dropping part of its most recent test is seems to be
the temperature—hotter than the sun. But in actuality, other fusion experiments have reached up into the billions of degrees and ion colliders like the LHC have been known to reach into the trillions.
The
really important part is how long the reactor was able to maintain that
plasma. Keeping plasma around and under control for a long enough time is one of the chief barriers to practical nuclear fusion.
The Wendelstein X-7 Stellerator's first successful test was only a
fraction of a second, though the team behind it hopes to be able to
extend that out to a whopping 30 minutes, citing the Stellerator's much
calmer operation. It was much, much harder to build than China's
Soviet-designed EAST, but should eventually prove easier to operate.
In
the meantime, however, EAST's feat is a true triumph that places it on
the leading edge of the nuclear fusion race. Other reactors of its
design have a hard time maintaining plasma of this temperature for 20
seconds before a reactor meltdown starts to be a concern, much less a
minute and 42.
Researchers
from EAST tell the South China Morning Post that their experimental
data may prove useful in the development of the International
Thermonuclear Experimental Reactor (ITER)
which is currently being built in France. That project has the lofty
goal of generating 500 megawatts through fusion power for 400 seconds. That sort of success might still be way off in the distance, but we are certainly taking steps towards it.
http://nextbigfuture.com/
Chinese experimental nuclear fusion reactor contained a 50 million degree plasma for 102 seconds
The goal of the Experimental Advanced Superconducting Tokamak was to
reach 100 million Kelvins for over 1,000 seconds (nearly 17 minutes). It
would still take years to build a commercially viable plant that could
operate in a stable manner for several decades.
Most of the tokomak devices built over the last 60 years have not been able to sustain for more than 20 seconds.
The team claimed to have solved a number of scientific and engineering
problems, such as precisely controlling the alignment of the magnet, and
managing to capture the high-energy particles and heat escaping from
the “doughnut”.
A team at the Max Planck Institute in Greifswald, Germany was able to
heat hydrogen to even more intense temperatures -- up to 100 million
degrees C -- but for much shorter periods of time. The German government
has dedicated more than £1 billion to the search for nuclear fusion
This $14-billion machine is set to usher in a new era of nuclear fusion power
By Jessica Orwig
February 19, 2016 4:28 PM
(ITER Collaboration) Picture of ITER under construction. The
first and largest machine of its kind is currently under construction
at the French scientific research center called Cadarache, which
specializes in nuclear power research.
It's called ITER, Latin for "The Way," and is expected to
usher in a new era of nuclear fusion-powered electricity — something
scientists and engineers have been working toward for over 40 years.
By fusing two forms of hydrogen, called deuterium and tritium,
together, the machine would generate 500 megawatts of power. That's ten
times more energy than it would require to operate.
Once completed, ITER would measure 100 feet in diameter and height,
representing a new breed of nuclear fusion device. If it reaches its
energy output goals, it will be the first machine of its kind to bridge
the gap from fusion research in the lab to readily available fusion
power for cities.
As of June 2015, construction costs for the machine exceeded $14 billion.
But, in the end, experts say it will be worth it. After all, nuclear
fusion is the process that powers stars like our Sun and offers a number
of advantages to current energy sources if we can harness that power
here on Earth:
Fusion generates non-radioactive waste that can be completely recycled within 100 years, unlike the toxic radioactive residue that today's nuclear fission reactors produce.
There's no chance of a runaway reaction because any malfunction would halt the fusion process, meaning that fusion reactors don't run the risk of a nuclear meltdown.
It's a clean source of energy compared to coal, natural gas, and crude oil.
Fusion reactors can run on seawater, offering a relatively renewable source of energy.
The problem with fusion
Right now, the biggest one is this: Fusion machines in operation
today use more energy to run than they put out, which is the exact
opposite of what you want from a power plant.
The problem stems from the super-heated plasma that machines, called
tokamaks, produce and where the fusion reactions takes place. Below is a
schematic of the plasma, shown in purple:
(Uploaded by Matthias W Hirsch on Wikipedia)
While
reaching these temperatures is a feat of engineering in and of itself,
tokamaks can't sustain the plasma flow for very long. The record for the
longest sustained plasma is 6 minutes and 30 seconds, which a French tokamak achieved in 2003.
This pulsing behavior, which comes with turning the plasma
repeatedly on and off in short bursts, is what scientists have been
trying to bypass for decades because pulsing costs too much energy to be
a viable approach for net energy gain.
Instead, the ideal approach is to build a machine that can produce a self-sustaining plasma. That's where ITER comes in.
Below is a cross section of what the inside of ITER will look like where the rotating particles are deuterium and tritium atoms:
The plasma inside ITER will
reach 150 million degrees, or ten times hotter than the center of the
Sun and enough to fuse deuterium and tritium.
An important byproduct of the
fusion is helium — specifically the nucleus of helium atoms. Once
produced, these atoms bounce around, imparting energy in the form of
heat, which helps to keep the plasma intrinsically hot, without the aid
of additional, external energy input.
"That's how it will be almost completely self sustaining,"Jonathan Menard, the program director of a major fusion facility at the Princeton Plasma Physics Lab (PPPL), told Business Insider.
This type of fusion burning is very similar to what's happening in the core of our Sun.
The future of fusion
(Science Magazine on YouTube) An illustration of Wendelstein 7-X's main plasma generator. Another machine in Germany called Wendelstein 7-X — which was recently turned on for the first time — is also expected to generate self-sustaining plasma.
However, Menard noted that it isn't likely that this machine
will generate enough surplus energy to serve as a potential nuclear
fusion power plant, which is what ITER is being designed to do.
Still another form of fusion reactors use lasers instead of plasma, like the National Ignition Facility in California, but that area of research still has a ways to go before it can compete with the tokamaks of the world.
"So far, the laser based systems are pretty inefficient an we think
the [plasma] fusion systems are closer to having net energy," Menard
said.
Construction began on ITER in 2007 and is expected to end in 2019
with the firing of its first plasma in 2020. The machine is expected to
reach full deuterium–tritium fusion experiments for potential net energy
gain by 2027.
In the mean time, fusion research facilities across the globe are using their tokamaks, like PPPL's National Spherical Torus Experiment, to explore different aspects of how ITER will operate.
"Particularly [we're investigating] how well those alpha particles or helium nuclei are confined," Menard said.
Check out a virtual tour through the ITER facility on YouTube, or below:
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