There's always a huge temptation in videos about nuclear fusion to quote the hackneyed
old cliche that it's a technology that's only 20 years away and always will be. "No doubt many of
you have heard the cliche phrase that nuclear fusion is just 20 years away and always will
be" So I promise you this time I definitely will not be using the cliche that nuclear fusion is
only 20 years away and always will be. Because to be completely honest, I'm not actually sure
the picture is even quite as optimistic as that. There's been a lot of press interest in apparently
major breakthroughs in nuclear fusion recently and just to be clear no one had been more delighted
than me to see commercially viable electricity generation from fusion power become a reality
because if it did it'd have pretty much solved the world's energy and resource scarcity problems in
one fell swoop. So, you know, I do see the appeal don't get me wrong! The slight wrinkle is that the
whole structure for gauging how well the various research centres are progressing appears to be
built on what a cynical person might describe as willful mass delusion. So what's going on?
Hello and welcome to Just Have a Think. It's a very compelling story isn't it,
the whole nuclear fusion thing? The dream is to reproduce the reaction that happens inside our own
sun where lighter elements like hydrogen and its isotopes of deuterium and tritium are converted
into heavier elements like helium. As the nuclei of these lighter elements are fused together
they emit neutrons and very large quantities of energy. We're talking about energy levels
about 10 million times greater than we can currently achieve by burning fossil fuels.
Nuclear fusion is in fact the process by which all elements in the universe were created in
the first place, which is why that nice man Mr Moby tells us we're all made of stars.
Lovely. In theory, by replicating that process in a controlled environment
here on earth you could get a relatively cheap and essentially unlimited amount of energy without
any greenhouse gas emissions and with only a tiny fraction of the radioactive nuclear waste
produced by the global nuclear fission industry today. And all of this coming from good old H20.
According to the Dutch high energy physicist LJ Reinders, who produced this mammoth 900 page tome,
there's an awful lot of hydrogen's heavier isotope, deuterium, in our oceans. To be more
precise, one in every six thousand four hundred and twenty atoms of hydrogen is deuterium.
And it can be literally scooped up isolated and utilized. As Reinders points out,
no mines are needed, no transport of fuel to power stations will be required because
you'll just build your power plant close to every coastline where your water supply will be
effectively infinite. And the fact that the fusion process itself produces no greenhouse
gas emissions means it could be the perfect solution to our present day climate emergency.
Almost sounds too good to be true doesn't it? And that's because it quite probably is. The
best funded experimental fusion reactors in operation today use designs known as
Tokamak and Stellarator. They're both examples of what's called magnetic confinement technology.
The International Thermonuclear Experimental Reactor or ITER has been in development since
1985. When construction work is finally completed in the latter half of this decade
it'll be the biggest tokamak machine on the planet. It originally had a budget
of 5 billion euros but it's now looking like it'll burn its way through more like 25 billion
with no guarantee of a successful outcome. It's basically a bunch of incredibly strong magnets
that contain a huge donut shaped stream of superheated plasma. The plasma is contained and
compressed by the magnets until the nuclei fuse together and release their energy as heat. That
heat then gets trapped in a specially created blanket that sits around the reaction chamber.
Then theoretically it's just a matter of piping that heat into water to create steam that goes
across a turbine and drives a generator that makes electricity. Sounds quite straightforward
in principle, but applying those principles to the real world has proven to be anything but easy.
First of all, getting plasma up to a temperature that's many times hotter than the surface of the
sun and keeping those streams of plasma in place long enough for fusion reactions to take place
is extremely challenging. China holds the current temperature record with their Experimental
Advanced Superconducting Tokamak or EAST, which in 2021 reached 160 million degrees Celsius.
That's more than 10 times hotter than the sun's core. So, you know, pretty impressive!
But they only managed it for 20 seconds and the power required to achieve it was enormous,
which is something we'll come back to in a moment. In late December 2021 another
experimental tokamak device called the Joint European Torus or JET, near Oxford in the UK,
achieved what they claimed to be the highest sustained energy pulse ever created
using a fuel made of equal parts deuterium and tritium. The JET tokamak produced 59 megajoules
of energy over a five second fusion pulse. That's about enough energy to boil 60 kettles and it's
twice the amount they achieved in their last record-breaking attempt back in 1997. But that was
25 years ago, so it's taken all this time to achieve that small incremental level of progress.
The experiment achieved a ratio of energy out to energy in, which the fusion community refer to
as Q, of 0.33 over the 5 second interval, and to be clear that means the energy they got out was
only one third of the energy they put in. And the Q they were referring to was specifically Q
plasma, which in nuclear fusion speak means the ratio of energy going into plasma to energy
coming out of plasma. It doesn't account for any other energy requirements for the overall system,
which is something else we'll come back to later. You may well also have seen an announcement in
2021 from the U.S Department of Energy's National Ignition Facility, who used a different technique
called Inertial Confinement, using laser energy instead of the magnetic confinement technique
used in tokamaks. They achieved a Q plasma of 0.7. It was big news at the time and the fusion
community was very excited by what they saw as a significant breakthrough. It meant that seventy
percent of the energy that went into the plasma came out again as a result of the fusion reaction.
OK, so that's getting another step closer to one for one right?
Well not really because we're only still talking about the energy in the plasma
not the entire system and the pulse lasted for less than four billionths of a second,
so I wouldn't go trying to switch your energy supply to Fusions R Us just yet!
Part of the problem is that as well as keeping them incredibly hot you also need to keep your
plasma particles moving in the right direction. The magnetic field in a tokamak's donut shape is
stronger in the middle and weaker at the edges, so there's a tendency for particles to drift
off course and hit the containment walls, and once that happens the reaction is over.
Stellarator reactors are an attempt to overcome this problem. Open up one of these devices and
you'll find the weirdly contorted twists of its vacuum chamber and containment magnets. It's a
shape so complicated that it had to be designed on a supercomputer at the Max Planck institute
in Germany and welded together by precision computer guided robots. There are 50 magnet
coils in here, each containing over a kilometre of superconducting cable weighing six tons designed
specifically to force particles through regions of high and low magnetic fields so that in theory
the effects of the two cancel each other out and keep the plasma away from the containment walls.
But whichever design you look at the fact is that firing up and running all the components of these
systems requires a massive amount of auxiliary power which is not reflected in that Q plasma
number we just looked at. So to truly consider how close the fusion bods are getting to a machine
that can actually produce useful electricity that you and I can use to make a cup of tea,
you have to look at what's called Q Total. Sabine Hossenfelder is a Physics PhD and research fellow
at the Frankfurt Institute for Advanced Studies in Germany. She also runs a YouTube channel
called Science Without the Gobbledygook, which no doubt many of you are already subscribed to.
Sabine made a brilliant video back in October 2021 explaining the whole 'Q' thing,
so if you want the deep dive then I'll leave a link to that video in the description box below.
In very basic terms though, if you're an investor looking to build a commercially profitable power
plant then you obviously need to know the total amount of energy required by the entire system
compared to the total amount of usable electricity your system will send into the grid. That's where
Q total comes in. It takes into account all the power required to run cool and
maintain the enormous magnets and all the other electrical and control systems
that keep the reaction going. It also factors in the efficiency of converting heat into steam
and driving the electrical generator, which is likely to be somewhere around 50 percent.
The ITER reactor that we looked at earlier is designed to have a power generation capacity
of 500 megawatts when it's completed and the team claimed to be aiming for a Q plasma of 10, which
is more than 14 times greater than anything anyone has so far achieved. But according to their head
of electrical engineering the whole system would actually require 440 megawatts of input power
to achieve a fusion generation capacity of 500 megawatts so the cube total in that case would be
500 over 440 which is about 1.14. Now that's not earth shattering but it's still better than break
even right? Well no because we still have to apply that heat to electricity conversion efficiency
of 50%, so now we're down to a Qtotal of 0.57. So even assuming that ITER does indeed one day
achieve its goals, which by the way it's nowhere close to even after 37 years of hard work,
then it'd still be consuming almost twice as much energy as it produces. And if we apply all those
numbers to the headline grabbing Q plasma of 0.7 that the U.S National Ignition Facility announced
last year, even if their lasers were measurably more efficient than magnetic containment methods
of Tokomaks and Stellarator, we're still left with a Q total that's almost certainly going to be far
less than 0.1. And here's another little reality check that I doubt the fusion bods are keen to
trumpet from the rooftops. Just using deuterium to drive the fusion reaction doesn't cut the mustard.
To reach even the modest numbers we've looked at today fusion reactors have to add tritium to the
mix like I mentioned earlier with the European JET facility. The combination of tritium and
deuterium results in a far higher production of neutrons from the fusion reaction, but tritium
is not abundantly available like deuterium. It's much rarer and much more expensive. And
unlike deuterium it's dangerously radioactive. If full-scale commercial fusion reactors ever came
into existence then to get enough tritium to make the reaction work they'd need to breed it
in the reactor by allowing some of the neutrons created by the fusion reaction to smash into atoms
of another element like lithium within the walls of the blanket that surrounds the fusion reactor.
Then there would have to be some way of extracting that newly created tritium from the blanket
and feed it back into the reactor, all without disrupting the magnets or the flow of the plasma.
Two small problems with that idea. Firstly it's never actually been demonstrated to work in the
real world, and secondly splitting atoms is not a nuclear fusion process it's a nuclear
fission process. That inevitably means that any prospective new fusion power plant of the future
would be subject to all the same tortuous and time-consuming regulatory constraints that tend
to cause such costly overruns in today's nuclear efficient power plants. I have to say I really do
admire the tenacity and dedication of the research scientists striving to achieve the ultimate energy
solution for our planet and I really do hope that one day in the future our descendants will enjoy
the fruits of their labour. But it looks very unlikely to happen in my lifetime and right now
we've got eight years to wean ourselves off fossil fuels, so I can't help wondering whether the tens
of billions of dollars being pumped into fusion research around the world might be better spent
on more immediate solutions that are already in place and well proven. Now I'm quite sure that
many of you will have your own very strong views on the subject of nuclear fusion and they may well
differ from mine so if you do then as always feel free to jump down to the comment section below
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