This is my friend Jade, creator of the Up and Atom channel. She makes these incredible math
and physics explainers that I absolutely love, and she recently got the opportunity to visit
ITER (eater) in France. You may have seen this place in the news: 35 nations working
together to build an enormous, industrial-scale nuclear fusion reactor. The size of the project
is mind-boggling. It’s been under construction since 2013, and… I like construction. So, when
Jade and I were chatting about her tour, she said, “Why don’t you just make a video about it too?!”
If everything goes to plan, ITER’s tokamak reactor will house plasma at temperatures
in the hundreds of millions of degrees, ten to twenty times hotter than the center of the sun,
hopefully paving the way for an entirely new form of electricity generation. I
don’t know much about superconducting coils or cyclotron resonance heating or breeder blankets,
but I do know it takes a lot of earthwork and steel and concrete to build the biggest
nuclear fusion reactor on earth. So let me give you the civil engineer’s tour of what
might be the most complicated science experiment in human history. I’m Grady,
And I’m Jade, and this is Practical Engineering. Today we’re exploring the ITER megaproject.
I was fairly new to fusion when I went to visit, and although I'm still no expert,
I still felt I should explain it rather than let a civil engineer. Before we dive into the
mechanics. Here's a question. Why is the world so interested in nuclear fusion? Basically, it comes
down to the huge potential payoff. If we could harness the power of nuclear fusion here on Earth.
It would be a way more powerful energy source than fossil fuels, without the environmental
baggage. This water bottle full of seawater plus one gram of lithium could provide electricity
to a family of four for a whole year. Unlike nuclear fission, there's no long lived waste
and no chance of nuclear meltdowns. It's a clean, sustainable and powerful energy source.
Some scientists go so far as to say that commercial nuclear
fusion is the next step for humanity. That's exactly what ITER, which translates to the way
in Latin aims to do. To nail down the technologies needed for a fully functioning commercial fusion
reactor. For you to get an idea of how ambitious their goal is, they plan to import 50 megawatts
of thermal power and get out 500 megawatts of fusion power, a gain of ten in fusion talk.
Nothing close to this has ever been achieved or even attempted in fusion history. So how
are they going to do it? Right in here. "So this is where the Tokamak is going to be
built?" This is the Tokamak pit where ITER is assembling the largest nuclear fusion
device in the world, a giant tokamak. Here's a man for comparison. It's going to be huge.
A tokamak is a nuclear fusion machine that works by magnetic confinement. It will hold about 840
cubic meters of piping hot plasma. Why plasma? Plasma is what the sun is primarily made of.
And it has the perfect conditions for fusion. To get fusion started in the ITER tokamak,
two isotopes of hydrogen, deuterium and tritium are pumped into a large donut shaped chamber.
This is just one of the six vessels that will make up the chamber. The fuel is heated to
temperatures of up to 150 million degrees celsius. When they fuse, the energy they
unleash is of epic proportions. But here's a question for you engineers. How is it possible
to contain so much plasma? No regular material can withstand those kinds of insane temperatures.
Imagine trying to hold onto a piece of the sun. These giant magnets produce magnetic
fields of almost 12 tesla, over 200,000 times stronger than Earth's magnetic fields. Plasma
is electrically charged. And just like iron filings align with magnetic fields,
so does plasma. How cool is that? But how does this fusion stuff actually
lead to electricity? ITER itself will not actually produce any electricity.
It's our learning ground, an experimental arena to fine
tune how a real reactor might operate. But in a real reactor, the walls of the
tokamak will be filled with cooling fluid. When the deuterium and tritium atoms fuse,
they release a neutron and a helium atom. About 80% of the energy released is carried
by the neutrons and being electrically neutral, they pass straight through the magnetic field.
When these high energy neutrons strike the tokamak walls, they heat up the fluid,
turning it into steam. Then, just like a regular power plant, the steam will spin turbines,
which will generate electricity. But how will ITER heat the plasma to such insane
temperatures? And when can we expect commercial nuclear fusion to get off the
ground? Check out my video after you've finished watching Grady's and find out.
Jade’s video goes into a lot more of the groundbreaking science at ITER, but all that
science requires a lot of actual breaking ground.
This is a bird’s eye view of the whole facility,
and this is where the Tokamak lives. So if all the nuclear fusion is going to happen in there,
what are all these other buildings and structures for? Fortunately, there’s a
civil engineer there in France amongst all the technicians and scientists who knows the answer,
and I was lucky enough to chat with him. This is Laurent Patisson, the civil engineering and
interface section leader at ITER, and he’s been there almost since the very beginning,
including taking delivery of some truly massive pieces of equipment.
Laurent walked me through the whole campus, and gave me an overview of how construction
is progressing across the facility. Many of those big deliveries get stored in one of the many tents
scattered around the site until they’re ready to be installed, and then onto one of the various
buildings. For example, the poloidal field coils that form superconducting magnets to help shape
and contain the plasma in the reactor are just too big to be completed offsite and shipped to ITER,
so instead, they built a manufacturing facility right on campus in this long building on the south
side. Similarly, the cryostat workshop was built to assemble the massive, vacuum-tight structure
that will surround the reactor and magnets. The cryostat parts, the poloidal field coils,
and lots of other truly large pieces of equipment destined for the Tokamak itself are then moved to
the adjacent assembly hall as needed. Pretty much every part of the Tokamak reactor is not only huge
but sensitive to environmental conditions too, so this building makes it possible to protect,
stage, assemble and install each one without having to worry about temperature or weather.
That’s about 21 stories tall and longer (and wider) than an American football field, end zones
included! And maybe the most critical part of the whole building is what runs along the top of it.
These two bridge cranes combine to become one of the largest cranes in the world with
a combined capacity of 1500 tonnes needed to assemble all the parts of the tokamak.
And everything has been tested and tested before each critical lift operation happens
with dummy loads before they do the real thing. But material and equipment aren’t
the only things flowing through this project site. There’s also a lot of electricity.
Imagine what your utility bill would be if your toaster got as hot as the sun!
ITER connects to the European power grid from a 400 kilovolt transmission line. During peak
periods of plasma production, the facility may need upwards of 600 megawatts! That’s
the capacity of a small nuclear power plant. Obviously you can’t just turn the reactor on
with a flip of a switch. ITER has to coordinate with the power grid manager to carefully time
the huge power draws with surrounding power plants to make sure it doesn’t cause brownouts
or surges on the grid. The 400 kV line feeds a large switchyard and substation on the ITER
campus. Electricity is stepped down to a lower voltage using transformers. Then it
flows through busbars, cables, and breakers to feed all the various buildings and equipment.
Like many electronic devices, the superconducting magnets that surround the tokamak run on direct
current, DC. So the AC power from the grid has to be rectified. For a phone or a flashlight,
an AC to DC converter looks like this. But at ITER, it takes up two full buildings. The
magnet power converter buildings have enormous rectifiers dedicated to each one of the magnet
systems. Once energized, those magnets can collectively store upwards of 50 gigajoues
of energy in their fields, though, so you also need a way to quickly get rid of that
energy if the magnets lose superconductivity (called a quench). Fast discharge units,
located in this building, allow ITER to dissipate that stored energy as heat in
a matter of seconds. There are also a lot of critical safety systems and parts to maintaining
the expensive and delicate equipment at ITER that require power 24/7/365. So,
there are two huge diesel generators that can provide backup power in case the grid goes down.
The flow of electricity is closely tied to the flow of heat through all the parts of ITER. Really
the whole thing is an experiment in heat, and there are so many ways things are being warmed
or cooled throughout the campus. Of course, you have heating, ventilation, and air conditioning
in all the buildings, and it’s not just for the comfort of the people working in them. Even tiny
temperature swings can affect the size of these huge components, complicating the assembly.
And it’s not just temperature, but humidity and cleanliness as well. So,
ITER has a robust ventilation and chilling system located in the site services building
along with a lot of the other industrial support systems like air compressors,
water treatment, pipes, pumps, and more.
Heat is also important for the electromagnets, which have to be cooled to cryogenic temperatures
so they act as superconductors.
That’s made possible by the Cryoplant, a soccer-field-sized
installation of helium refrigerators, liquid nitrogen compressors, cold boxes, and tanks that
keep the various parts of the tokomak supercool during operation. But, although some parts of
the machine have to be cryogenically cooled, to create nuclear fusion, you need to heat the plasma
to incredible temperatures, and there’s three external heating systems at ITER. One, called
neutral beam injection, fires particles into the plasma where they collide and transfer energy.
The other two, ion and electron cyclotron heating (say that three times fast), use radio waves, like
huge microwave ovens. Those systems are located in the RF Heating building near the Tokamak complex.
And then there’s the matter of the heat output. The whole point of exploring nuclear fusion is
to use it as an energy source, to convert tiny amounts of tritium and deuterim into
copious amounts of heat. ITER’s goal is to produce a Q of ten, to get ten times as much
thermal energy out as it puts into the reactor. But there’s no electrical generator on site. In
a commercial fusion facility, you would need to convert that output heat to electricity,
probably using steam generators like typical nuclear fission plants. That part of the
process is pretty well understood, so it’s not part of this research facility. Instead,
ITER needs a way to dissipate all that heat energy they hope the fusion will create. That’s the job
of the water cooling system and the enormous cooling tower nearby. Water is circulated
around the tokomak and then to the tower where it can reject all that heat into the atmosphere.
That brings us back to where we started, the Tokamak complex itself. That machine,
once its finished, will weigh an astounding 23,000 tonnes, more than most freight trains. And with
all the heating and cooling going on, there are some serious challenges in just holding the thing
up. As the tokomak is cooled cryogenically, it shrinks, but the building stays the same size.
And, because, you know, this is an actual nuclear reactor, it has to follow all the
safety regulations of any nuclear power plant. No one will be inside the Tokamak complex when it’s
running. They’ll be nearby in a separate control building, physically distant from the reactor.
And the complex itself has been engineered to withstand a host of disastrous conditions,
from floods to plane crashes to explosions on the nearby highway. Like all nuclear power plants,
it has a containment structure to confine any fusion products that
might be released into the atmosphere in the event of an accident. And that’s made
using a special concrete formula developed over two years just for this application
that contains extra heavy aggregate and boron to provide radioactive shielding.
And, it’s not just thermal movement that the designers planned for,
but seismic movement too. An earthquake could ruin the entire structure in an instant if
the Tokamak was violently shaken, so engineers had to get creative.
Big thanks to the folks at ITER for taking the time to help me understand all this. I
only had time to scratch the surface of all the incredible engineering involved. And, go check
out Jade’s video to learn more about this awesome project; she actually got to be inside some of
the buildings we showed. The civil engineering at the Tokamak building just wrapped up, but there’s
a long way to go before fusion experiments start. Like all ambitious projects, this one
has struggled through its share of setbacks and iterations. But with 10 times the plasma volume
of any fusion reactor operating today, they’re hoping to eventually demonstrate the potential
for fusion as a viable source of energy. And that might eventually change the world. Only
time will tell if it happens, but it’s exciting right now to see countries across the world
collaborating on such a grand scale to invest in the long-term future of energy infrastructure.
Innovation in energy infrastructure is one of those topics that you can understand from wildly
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