
Chinese Tokamak reaches over 100M degrees - 7ero
http://english.hf.cas.cn/new/news/rn/201811/t20181113_201186.html
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i_am_proteus
A tokamak is a kind of fusion reactor, and basically the most prevalent.

"100M degrees" (Kelvin) corresponds to 10 KeV (kilo electron volts), which is
an important figure to exceed for D-T fusion. D-T fusion which is the kind of
fusion the ITER Tokamak (a forthcoming fusion reactor and international
megaproject) intends to demonstrate.

An older fusion experiment, JET (Joint European Torus) reached these levels,
so this does not break new ground, but it is important if this Chinese Tokamak
is going to provide data useful for ITER.

I will note that it's rather unusual to refer to plasma temperature in Kelvin
rather than in KeV. I edited this comment with a few more details to try to
make it easier for laypeople to understand.

~~~
maaaats
> _" 100M degrees" (Kelvin)_

Off topic, but this distinction made me laugh. Like the difference between
Kelvin and Celsius would throw everything off.

~~~
marcosdumay
Well, there is almost certainly somebody that read the number and thought
about Fahrenheit.

~~~
hkt
Do scientists use farenheit? Genuine question

~~~
sandworm101
Some. Not the physicists or astronomers, but some Americans who work with data
from non-scientists regularly stay with the units in the data. Some engineers,
those who are dealing with older equipment, stick with the units used when the
equipment was built. US pilots and aerospace generally still talk in knots and
feet of altitude.

~~~
jschwartzi
Mountain climbers in the US typically also use feet for elevation. Compasses
sold in the US also have different markings for measuring the Universal
Transverse Mercator grid(1:24,000 and 1:50,000 in the US) and rulers(inches,
feet). 1:24,000 is used on USGS 7.5-minute maps, and I believe 1:50,000
originates from an older map series, both of which have topographical lines
marked in feet instead of meters. Altimeters sold in the US also customarily
use feet although the digital ones can be switched to Meters.

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mrpdaemon
The main challenge in working with these high temperature plasmas is
confinement. In order to achieve nuclear fusion matter needs to be heated to
immense temperature, so that the kinetic energy of nuclei colliding can
overcome the electrostatic force of the protons pushing each other away and
"fuse" into larger nuclei (held together by the "strong force"), converting a
fraction of the reaction mass into a relatively large amount of energy in the
process.

In order to keep the plasma at the temperatures where fusion can occur, rather
extreme measures have to be taken. In the Tokamak approach, the plasma is
placed in a toroidal vacuum chamber, and "suspended" in the center of the
torus by using electromagnets that line the Tokamak chamber's walls. At such
high temperatures the plasma is so energetic that it is very hard to contain
such fast moving particles. If the plasma "escapes" the confinement and
contacts anything (ie. the walls of the Tokamak) it rapidly cools down to
temperatures below where fusion can happen.

The immense engineering challenge here is to heat plasma to ridiculous
temperatures, and keep it confined in a very small volume at great temperature
and pressure to mimic conditions that give rise to nuclear fusion in the
center of stars.

~~~
qwerty456127
> If the plasma "escapes" the confinement and contacts anything (ie. the walls
> of the Tokamak) it rapidly cools down to temperatures below where fusion can
> happen.

Sounds relieving. I used to think that «if the plasma "escapes" the
confinement and contacts anything (ie. the walls of the Tokamak) it rapidly…»
disintegrates everything around or, when the power is huge enough, causes an
apocalypse…

~~~
sergiosgc
At those temperatures, it will disintegrate whatever it touches. It's just
that, unlike fission, fusion is unstable[1] so it quickly fizzles out, and
damage will be local.

[1] Unstable in the sense that it is hard to maintain fusion conditions, not
in the Hollywood sense that it blows up if you look at it sideways.

~~~
robin_reala
It’s not particularly hard to maintain fusion conditions, you just need a
stellar mass levels.

------
agoldis
Okay, did some search:

\- When two hydrogen nuclei combine, they produce an enormous amount of
energy. That process is known as nuclear fusion.

\- Light nuclei have to be heated to extremely high temperature, it is
challenging to create a controlled, safe fusion reactor that offers more
energy than it consumes. Once we have such we’d have a near-limitless source
of clean energy.

\- Nuclear fusion does produce radioactive waste. However, in contrast to
fission produced wastes, they are short lived and decay to background levels
in a very short time.

\- Tokamaks try to do just that.

~~~
i_am_proteus
I will add:

\- While the products of the fusion reaction are short-lived, operating a
fusion reactor will active materials in the reactor and create some longer-
lived radioisotopes.

\- Unlike a fission reactor, which is loaded with months to years worth of
fuel, a fusion reactor would have fuel constantly injected. So operator action
to stop injecting fuel would stop the nuclear reaction.

~~~
afraca
Can either you or your parent poster say what "short lived" and "longer-lived"
would be roughly?

~~~
Nimelrian
Longer-lived would be thousands of years for the steel structure until it is
manually handable. 50-100 years for remote handling.

> It was shown that wait times are required in the order 50–100 years for the
> remote handling recycling option and hundreds (Li4SiO4) to thousands
> (Eurofer) years for hands-on handling.

Source:
[https://doi.org/10.1016/S0022-3115(02)01273-4](https://doi.org/10.1016/S0022-3115\(02\)01273-4)

------
jabl
As there seems to be quite a lot of confusion in this thread about what this
is, here's an excellent video giving an overview of the state of the art in
fusion energy research that is understandable by a lay audience:
[https://www.youtube.com/watch?v=L0KuAx1COEk](https://www.youtube.com/watch?v=L0KuAx1COEk)

(somebody posted that video on another recent HN fusion thread)

~~~
joosters
Thank you for (re)posting that video, it's an excellent introduction/overview.

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nickdothutton
Is it just me, or have we converged on 1 reactor design (the tokamak)
relatively early on in the process? I appreciate that funds need to be
concentrated in order to have an impact, but we have built dozens of this
design since the 1950s, yet here we are.

~~~
majewsky
Wendelstein 7-X in Germany is a stellarator-type reactor:
[https://en.wikipedia.org/wiki/Wendelstein_7-X](https://en.wikipedia.org/wiki/Wendelstein_7-X)

~~~
tim333
And YC is invested in Helion Energy using pulsed inertial fusion. Though the
tokamak seems closest to being functional. The MIT ARC design is theoretically
supposed to be able to work, at least on paper:

>The ARC design aims to achieve an engineering gain of three (to produce three
times the electricity required to operate the machine) while being about half
the diameter of the ITER reactor and cheaper to construct. (Wikipedia)

It's not been built because of the $5bn or so cost, though given global
warming / saving the planet type issues I'd be happy enough as a tax payer to
have governments fund one and maybe knock 1% off the defence budget to counter
that. It'd probably do more for world peace than churning out some more f35s.

~~~
DennisP
ARC has some funding now. They spun off a startup called Commonwealth Fusion
Systems, which has $50M so far, from an Italian oil/gas company.

[https://en.wikipedia.org/wiki/Commonwealth_Fusion_Systems](https://en.wikipedia.org/wiki/Commonwealth_Fusion_Systems)

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nscalf
Since I don't see any comments mentioning this, I've heard a lot of talk about
skepticism on other forums regarded Chinese scientific breakthroughs. I know
on the state level, their numbers are not considered reliable (economic data
for instance). Does anyone have thoughts on the reliability of this?

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Santosh83
Let me ask a different question to the knowledgeable folk here. It has been
noted that producing the temperature is not the hardest part but confining the
plasma for long periods of time is.

On this note, do we have any reason to be particularly confident that magnetic
confinement will ever break even and produce surplus energy? In nature fusion
seems to occur through gravitational compression, so what makes us sure that
we can simulate this by other means that will ever amount to more than just
demonstrations?

~~~
thinkcontext
ITER is designed to address exactly what you have asked.

"The ITER thermonuclear fusion reactor has been designed to produce a fusion
plasma equivalent to 500 megawatts (MW) of thermal output power for around
twenty minutes while 50 megawatts of thermal power are injected into the
tokamak, resulting in a ten-fold gain of plasma heating power."

[https://en.wikipedia.org/wiki/ITER](https://en.wikipedia.org/wiki/ITER)

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_Microft
As far as I know temperature is one of the important but not the only
important parameter. Density and confinement time can be taken into account as
well to get a number that better characterizes the performance of a reactor,
iirc.

 _Edit:_ I think this is what I meant:
[https://en.wikipedia.org/wiki/Lawson_criterion](https://en.wikipedia.org/wiki/Lawson_criterion)

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dmos62
Can someone comment on what kind of economic effect that working fusion
reactor technology would have?

I hear sometimes contradictory hear-say on the lines of "unlimited energy",
"reactor would have to be fed constantly".

~~~
quotemstr
I'm not sure that it would have a profound effect at all. Fission is very
power dense as well and fission fuel cost is not the primary driver of overall
costs in existing nuclear designs.

Fusion might end up looking a lot like fission, but hopefully with a lower
perceived safety risk and thus more public acceptance.

Granted, modern fission designs aren't _actually_ unsafe, but that doesn't
matter for PR purposes.

~~~
dmos62
Yeah, that's what's bittersweet about these technologies and policy in
general. They're held back by PR.

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agoldis
Please explain what does it mean and why is it good? :) Thank you.

~~~
saagarjha
It’s an important milestone in the search for sustainable nuclear fusion.

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gwbas1c
I know very little about fusion.

Did the reactor produce more energy then was put into it? I just don't
understand enough about the field to figure that out by reading the article.

~~~
DennisP
No, they've just reached fusion temperatures. It's a step along the way but
we're not at net power yet.

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argc
100M seems insanely high, beyond what anything man made would be able to
contain. Is it extremely short lived? Or over a very small area? Very
interesting.

~~~
NamTaf
It is incredibly high. We hold it in not by any material, but by magnetic
fields. Plasma has the handy feature of being magnetic. The Tokamak[1] design
used in ITER and this example uses a whole heap of magnets to hold this plasma
in a doughnut-shaped area.

[1]:
[https://en.wikipedia.org/wiki/Tokamak](https://en.wikipedia.org/wiki/Tokamak)

~~~
arez
Doesn't it take a lot of energy to have such a big magnetic field?

~~~
whatshisface
Fundamentally it doesn't have to, because like a weight resting on the top of
a ladder magnetic fields store energy and do not dissipate it. In practice it
does because our ways of producing and maintaining strong magnetic fields
require a lot of upkeep. This, like most things in fusion, is an example of
where the realities of present day engineering are far cruler than the laws of
physics.

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conjectures
Anyone know what the 'standard' and state of the art approaches to inference
are for fusion?

I.e. going from sensor readings to inference of the plasma state.

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creeble
How are these results more (or less) significant than the stellerator
(Germany) achieved earlier this year?

I thought the stellerator had already achieved 100M Kelvin?

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rio517
If you added one gram of 100M degree material in a 5 sq meter room at 15
degrees C, how hot would the room get?

~~~
emeijer
Well.. assuming the room is about 3 meters high, that's a room volume of 15
cubic meters. Assuming it's filled with air, and air weighs about 1,29 kg per
cubic meter, that's 19,35 kg or 19350 grams of air. 15 degrees C is 288
Kelvin, so that's 19350*288 = 5.572.800 gram-kelvins of energy in the room
initially. Now we add 100.000.000 gram-kelvins (the one gram of hot stuff) to
it, and assuming this energy distributes over the air contents, our air now
has a heat energy of 105.572.800 gram-kelvins. Dividing it back the same way
(over the 19350 grams of air) gives us 105572800/19350 = 5456 gram-kelvins per
gram of air, so a temperature of 5456 kelvins or 5183 degrees C. Still pretty
hot.

------
adtac
Once we achieve sustainable fusion, will it be possible to "share" the energy
with everyone else to create more independent fusions? Kinda like keeping the
candle burning so as to light more candles because matches are too costly.

Now, I don't expect politics to allow sharing of fusion energy to help other
countries.

~~~
hoffs
Isn't fusion reactor basically infinite energy, I mean sure it makes total
sense to no share it with other because you can sell your free energy for
cash, but considering that a lot of global scientists work on it and most of
the findings are published, don't think that such strategy would last long.

~~~
jabl
Just like previous predictions that the introduction of fission power plants
would result in electricity 'too cheap to meter', I suspect the same will
happen for fusion. Even if the fuel is nearly free, you still have to build
and maintain the power plant, the grid etc., neither which is cheap.

But yes, the first ones to 'crack' the problem will have a head start in the
commercial fusion power plant market, but I don't think it will last very
long. As you say, most of the research is being published, and even if
somebody manages to initially keep that final 'dot on the i' secret, it
wouldn't take other researches long to figure it out.

~~~
Balero
From what i've read[0] it will remove about a third of the cost (probably
less). About a third of energy cost goes on fuel (now almost 0), a third on
the grid, and a third on the station (now probably more).

Whilst a 20-30% reduction in energy cost would be great. The really important
change is that it is much more scalable and easy to get. You don't need to dig
up coal, or drill for oil. All of which can be limited. With a working fusion
reactor a country like Singapore can be energy independent, in a way it never
could with any other type.

This independence would mean no more need to mess around in areas with these
resources (think middle east) or have your countries energy rely on a third
party you'd rather not rely on (think Germany and others and their reliance on
Russian gas)

[0] A Piece of the Sun: The Quest for Fusion Energy - throughly enjoyed this
book.

~~~
philwelch
Even though the cost of energy is divided by thirds, fusion still generates so
much more power that the sheer scale can overpower lots and lots of
bottlenecks.

For instance, it is chemically possible to combine water (either atmospheric
or from a normal water source) with atmospheric CO2 to chemically synthesize
hydrocarbons. It just takes energy. So you could have a single, absolutely
massive fusion plant next to an atmospheric fuel refinery and use the
hydrocarbons for fuel storage and distribution. You could do likewise with
hydrogen and oxygen if you wanted to make fuel cells or rockets. And this
would probably be cheaper than refining fossil fuels. You could actually run
OPEC out of business this way, make the electric car obsolete, make airlines
carbon-neutral, etc., etc.

Climate change? Just extract the atmospheric CO2 using cheap fusion energy and
turn it into an easily sequestrable form. Nitrogen fertilizers? You can make
those from the air too. Drought? Use fusion power to run desalination plants.
Arable land becomes a non-issue with fusion because vertical farming becomes
easy. Every city could just grow whatever they needed in exactly the right
climate conditions in a set of enclosed vertical farms, though they might not
need to because energy will be so cheap that there's no problem shipping the
stuff from Honduras anyway.

Computation scales with power, too. More power, more computation, except
computation produces heat, which you need even more power to chill.

~~~
Balero
That's a great explanation of some of the benefits! These are the most
important in my opinion: "You can make those from the air too. Drought? Use
fusion power to run desalination plants. Arable land becomes a non-issue with
fusion because vertical farming becomes easy." You could also use this water
to stop desertification, which would be a great thing.

I do disagree with you on Hydrogen fuel cells replacing electric cars though.
I think battery powered cars will be better than hydrogen powered ones. The
power storage is more reliable, and the power transfer is more simple (lines
as opposed to truck delivery or pipeline. And if we assumed that it would be
done on site at stations, then they would already have power lines, so just
use that!)

~~~
philwelch
> I do disagree with you on Hydrogen fuel cells replacing electric cars
> though.

Not what I meant to imply. You’d just use old-fashioned hydrocarbons, except
reconstructed from atmospheric CO2 and water.

------
docker_up
Stories like this scare me. With all of the precautions, even things like
Fukushima failed and will poison our ocean for millennia. What happens if we
have a runaway fusion process through some pathway that was unexpected?

With all the talk about the LHC possibly producing mini blackholes or magnetic
monopoles that could potentially cause protons to decay spontaneously, I don't
have enough nuclear physics background to know whether we are inherently safe,
or if there is a real risk here.

~~~
Quenty
Fusion is not a chain reaction. The energy maintained for this is incredible
and it can’t run away. Fusion has no toxic or radioactive bioproducts.

As a power source fusion is pretty good, which is why it’s such a target for
research.

See: [http://www.fusenet.eu/node/38](http://www.fusenet.eu/node/38)

~~~
throwaway_se099
> Fusion has no toxic or radioactive bioproducts.

D-T fusion, which is the easiest to achieve and perhaps sustain, directly
produces He nuclei (that is, alpha particles) and rather energetic neutrons at
14 MeV. Those neutrons, aside from being a form of ionizing radiation
themselves, are bound to transmute some of the surrounding material into
radioactive isotopes. So, I don't think that "no toxic or radioactive
byproducts" is correct. However, the results _are_ easier to handle than those
of fission reactors.

------
w323898
Fusion was, and for the foreseeable future will be, a boondoggle. In the US it
was a cold-war-era arms race program intended to scare the USSR and have them
overextend, and now the Chinese are using it for propaganda and scientific
Keyensianism.

The fact is, fusion generates neutron radiation that destroys the reaction
vessel, making it an unviable technology. Nobody takes it seriously as a
source of energy, aside from uninformed people. As cool as the idea of
controlled fusion is, it is and will remain science fiction.

~~~
dbingham
I dunno, my buddy who just got a degree in high energy plasma physics working
on fusion reactors might disagree with you.

And really, you just sound like every crank ever who thought X technology was
totally unfeasible and always would be -- until it wasn't. So currently
attempts haven't found a solution to the reaction vessel destruction problem.
That does not mean someone in the future couldn't figure that one out.

~~~
jeffreyrogers
OP at least gave a reason: neutron radiation destroys the reaction vessel. No
one who's responded has given any evidence for why this is false.

~~~
eutropia
It's not false. But it's also not a universal constant like the speed of light
or something, absent a reason why it couldn't be planned for and dealt with,
I'm inclined to treat it as an as-yet-unsolved engineering challenge.

