
Wendelstein 7-X achieves world record - _fizz_buzz_
http://www.ipp.mpg.de/4413312/04_18
======
blattimwind
Just to reiterate, Wendelstein 7-X is _not_ about fusion. 7-X is a research
project about controlling a plasma. It is not meant to evaluate whether energy
production is viable, neither is it setup to do so.

~~~
darawk
> 7-X is a research project about controlling a plasma.

Which is the primary impediment to developing viable fusion reactors. So yes,
it is absolutely about fusion. We're not trying to contain plasma because we
think it'd be a neat thing to do. We're trying to contain plasma because it's
necessary for fusion.

We already know that energy production is viable if we can solve the
containment problem. Saying this project "isn't about fusion" is like saying
"guns don't kill people, bullets do".

~~~
jnxx
> We already know that energy production is viable if we can solve the
> containment problem.

No. That's only a small part of the problems. What is probably a far more
difficult problem is the fact that any nuclear fusion which is remotely viable
in this century will use a Deuterium-Tritium reaction. And tritium is an
isotope which does not occur in nature - it is unstable. Therefore tritium has
to be bred, using heavy water reactors. And lots, lots, of uranium. The idea
is now to breed tritium, using neutrons from nuclear fusion, and further
nuclear chemistry which is supposed to happen in a breeding blanket. But this
runs into an additional problem, the deuterium-tritium reaction has no neutron
surplus, as uranium fission has. And in addition to the very difficult task of
exfiltrating traces of Tritium, one essentially needs a breeder technology
(similar to Monju in Japan), and there are huge, unsolved material sciences
problems, such as constructing a large structures which withstands very strong
magnetic forces, very high temperatures, and a very high neutron flux, and
this of course without any elements like carbon which will become
radioactively activated.

Oh, and I forgot, the whole process is also unlikely to be clean, because of
the breeder technology needed.

And all these questions are so extremely difficult, that today's large
projects, like ITER, do not even address them.

More on these issues for example in the article by Michael Moyer which is
contained in the page below (Michael Moyer, "Fusion's false Dawn", Scientific
American 302, 50 - 57 (2010) doi:10.1038/scientificamerican0310-50 )

[http://energyskeptic.com/2014/why-fusion-is-
still-30-years-a...](http://energyskeptic.com/2014/why-fusion-is-
still-30-years-away/)

~~~
philipkglass
Tritium can be bred in any sort of fission reactor. The US has recently used
light water power reactors to breed tritium for supplying the US nuclear
weapons stockpile.

Lithium-7 plus a high energy neutron yields tritium, helium, and a lower
energy neutron. I don't know what a practically engineered system can do, but
a 14.1 MeV neutron from D-T fusion formally has enough energy to transmute 5
lithium-7 nuclei into tritium and helium (each transmutation is endothermic to
the tune of 2.466 MeV).

I agree about the huge unsolved material science problems. I just don't think
that tritium availability lies on the critical path of unsolved problems for
industrial fusion power.

~~~
jnxx
> I just don't think that tritium availability lies on the critical path of
> unsolved problems for industrial fusion power.

Well.

[https://scholar.google.co.uk/scholar?hl=en&as_sdt=0%2C5&q=Sa...](https://scholar.google.co.uk/scholar?hl=en&as_sdt=0%2C5&q=Sawan+Abdou+Tritium+breeding&btnG=)

[http://fti.neep.wisc.edu/pdf/fdm1273.pdf](http://fti.neep.wisc.edu/pdf/fdm1273.pdf)

M.E. Sawan and M.A. Abdou, "Physics and Technology Conditions for Attaining
Tritium Self-Sufficiency for the D-T Fuel Cycle", Presented at the Seventh
International Symposium on Fusion Nuclear Technology, May 22-27, 2005, Tokyo,
Japan; to be published in Fusion Engineering and Design.

Abstract + conclusions:

"There is no practical external source of tritium for fusion energy
development beyond ITER and all subsequent fusion systems have to breed their
own tritium. To ensure tritium self-sufficiency, the calculated achievable
tritium breeding ratio (TBR) should be equal to or greater than the required
TBR. The potential of achieving tritium self-sufficiency depends on many
system physics and technology parameters. [...] It is clear from the above
discussion that both the required and achievable TBR values depend on many
system physics and technology parameters. Many of these parameters are not yet
well defined. In addition, the rapidly decreasing tritium resources imply that
the time window for the availability of tritium to supply fuel for the DT
physics devices is closing rapidly. It is, therefore, necessary to establish
without delay an extensive R&D program to determine the “phase-space” of
plasma, nuclear, material, and technological conditions in which tritium self-
sufficiency can be attained.

[...] Tritium self-sufficiency in DT fusion systems cannot be assured unless
specific plasma and technology conditions are met. [...]

~~~
philipkglass
This seems to be the critical assumption in Sawan and Abdou's paper:

 _The tritium bred in the CANDU reactors is the only practical source
available for ITER and other DT fusion systems [3,4]._

Citation 3 is "personal communication." 4 is this 2002 presentation:
[http://www.fusion.ucla.edu/abdou/abdou%20presentations/2002/...](http://www.fusion.ucla.edu/abdou/abdou%20presentations/2002/DevPath%20Presentation/DevPath%20Presentation%20\(10-28-02\)%20FINAL2.pdf)

Page 32 of that presentation, "Tritium Supply Calculation Assumptions", says
it is assumed that the following will NOT happen:

• Restarting idle CANDU’s

• Processing moderator from non-OPG CANDU’s (Quebec, New Brunswick)

• Building more CANDU’s

• Irradiating Li targets in commercial reactors (including CANDU’s)

• Obtaining tritium from weapons programs of “nuclear superpowers”

• Premature shutdown of CANDU reactors

But assumptions 3 and 4 have already been invalidated. China has added CANDU
reactors since the presentation and is building a few more abroad for other
countries. The United States has started irradiating lithium targets in
commercial reactors.

So in my judgment, closing the tritium cycle still isn't on the critical path
to fusion industrialization. There are other crucial problems to solve before
"where will we get enough tritium for these fusion reactors?" becomes a
crucial issue.

------
saganus
What does "At an ion temperature of about 40 million degrees" mean?

How does "ion temperature" relate to "regular" temperature?

Is it similar to how we can cool down things to fractions above absolute zero,
by using lasers to reduce the movement of atoms? i.e. is the "ion temperature"
a measure of how fast are they moving, as opposed to the every-day meaning of
temperature as "how hot something is"?

I realize that "how hot something is" depends on how fast the atoms of said
"something" are moving, but since they specify "ion temperature" I'm guessing
it has a very specific meaning.

I searched for "ion temperature" but only found about Electron temperature
[0].

Could someone explain it to me in lay terms? :)

[0]
[https://en.wikipedia.org/wiki/Electron_temperature](https://en.wikipedia.org/wiki/Electron_temperature)

~~~
contact_fusion
Other replies have explained that the ions and electrons can be at different
temperatures, and that is of course true. I can offer some more explanation
why. While you have linked temperature to some average kinetic energy, this is
not a strictly accurate notion of temperature. Temperature only means
something in the context of thermodynamic equilibrium; for any system out of
equilibrium, often a temperature cannot be defined, even as an average kinetic
energy. The two concepts are linked to each other, in the sense that an
average kinetic energy at the particle scale is a significant (and sometimes
only, but not always) component of the internal energy of the system. But
temperature is first and foremost an equilibrium concept.

A plasma is composed of both ions (partially ionized atoms, or if they are
fully ionized, bare nuclei) and electrons. Together, they constitute two co-
located but separate fluids, whose motions may be distinct; indeed, because
electrons are so much lighter than ions, they respond to forces much more
readily. In equilibrium, a single fluid must have sufficiently rapid
interactions so that the particle distributions are driven to a Maxwellian. In
that case, for a single fluid, a temperature is well defined. In the case of a
two-fluid system, self-interactions (such as interactions between ions and
themselves, and electrons and themselves) may be sufficient to establish two
separate equilibria corresponding to each fluid; hence, the electron vs. ion
temperature. Only in the case that ion-electron interactions are sufficiently
rapid would those equilibria be driven together to a single-temperature fluid,
in which case, Te = Ti.

This picture becomes rapidly more complicated at very high temperature
(usually, around 0.1 keV or about a million K), at which point the photons
being exchanged by hot charged particles become dynamically important, and a
third temperature, the radiation temperature, may emerge. At this point, the
plasma must be described using three temperatures - if, and only if, you are
in a situation lucky enough for equilibrium to manifest. (Fortunately,
equilibrium is not usually that hard to access.) In many cases, such as when
the system undergoes a strong shock, the system may be driven very far from
equilibrium, but only temporarily. In others, some underlying energetic
process may continuously drive the system away from equilibrium, resulting in
a metastable state; this is the case in stellar atmospheres, in which NLTE
(non-local thermodynamic equilibrium) processes matter a great deal. Usually,
physicists resort to kinetic theory to try to understand such situations.

~~~
saganus
Awesome explanation!

Thanks a lot.

It's amazing how something seemingly simple as "temperature" can be so
counter-intuitive.

------
maxxxxx
If you speak German the podcast Alternativlos has a fantastic episode about
Wendelstein. Highly recommended.

~~~
sschueller
Did you mean this one
[https://alternativlos.org/36/](https://alternativlos.org/36/) ?

~~~
maxxxxx
That's the one.

~~~
kaeluka
Thanks for the tip, started out really interesting!

~~~
krylon
Even if you don't care about fusion itself, it is highly interesting in that
it covers some of the engineering that went into building that thing.

~~~
maxxxxx
And the guests are perfect. Competent and entertaining at the same time.

------
epistasis
> The objective of fusion research is to develop a power plant favourable to
> climate and environment. Like the sun, it is to derive energy from fusion of
> atomic nuclei

While plasma containment seems like an essential step towards fusion-based
energy, is fusion-based energy a desirable goal?

Right now, fission-based nuclear energy is only used as a heat source for
steam-driven turbines. It's a fantastically complex and expensive way to make
heat.

Is fusion energy on Earth going to do something similar? And if so, is this
source of heat actually going to be cheaper than using the sun as a distant
fusion reactor? (Which is what drives both solar and wind energy on Earth.) It
seems quite doubtful that fusion could ever be cheaper than solar or wind
energy, the tech-to-energy ratio just seems massive in comparison.

So if it's not Earth where fusion energy will be useful, how about in space?
Here on Earth, the Carnot cycle is used to convert heat into useful mechanical
energy, then finally electrical energy, which is usually the true goal. But
the Carnot cycle requires dissipating massive amounts of heat; just as much
energy is dissipated as heat as gets turned into electricity. And heat
dissipation isn't such an easy thing in space, is it?

I feel like I'm missing some rather large puzzle pieces here. Without them,
fusion does not really seem like an engineering goal towards a good energy
source, just engineering research into better containment of difficult
materials. Could somebody help enlighten me?

~~~
rohit2412
Just a layman. But wind and solar have big limitations. They are available
only in a limited amount only under certain conditions and their variability
isn't under our control. And if you think energy storage would solve all this,
batteries aren't cheap. We would like to have an infinite source of energy
that we can control on demand.

~~~
rock_hard
Oh, but a fusion power plant is gonna be cheap?

~~~
rohit2412
Who knows about the future. And considering the amount of energy feasible via
fusion, it can be insanely cheap in terms of price per kwhr

------
rurban
General comparison of the two competing systems: Tokamak vs Stellerator
[https://www.sciencedirect.com/science/article/pii/S2468080X1...](https://www.sciencedirect.com/science/article/pii/S2468080X16300322)

Looks like theoretically the Stellerator is superior in practice, while in
practice only the Tokamak is being worked on practically.

~~~
nabla9
Fortunately the ITER project does wast amount of R&D and basic engineering
that solves problems common to both design. If the problems in stellators are
solved and it proves to be superior to tokamak in practice there is no need to
start from scratch.

~~~
ygra
There's also quite a bit of talk going on between scientists on both projects.
If I remember correctly, the microwave heating design of Wendelstein 7-X also
solved a few problems for ITER and in general it's more of a friendly
competition.

~~~
azernik
I view it as less of a competition than as projects working on different parts
of the same problem - ITER seems to be working more on the problems of
managing a fusion reaction (materials, procedures, shielding, etc.), while
using a better-studied containment design with lower technical risk.
Meanwhile, Wendelstein is ignoring all those other challenges in order to
study an alternate containment design in isolation.

------
xinyhn
Anyone interested in the subject matter would probably enjoy Omega Tau
Podcast.
[http://omegataupodcast.net/tag/fusion/](http://omegataupodcast.net/tag/fusion/)

------
pfdietz
Whenever you're shown a new gosh-wow fusion design, ask "What is the power
density of this design?"

The power density of a PWR fission reactor core is 100 MW/m^3.

The power density of ITER (gross fusion power/volume inside the cryostat) is
maybe 0.05 MW/m^3.

There are fundamental engineering limits to fusion that guarantee the power
density will suck compared to fission. So my default take on any fusion design
is that it will never be competitive with fission, never mind the things that
are cheaper than fission.

------
tzahola
How’s Lockheed’s Z-pinch based compact reactor?

~~~
topspin
Latest news is a patent grant to Lockheed in March. Not much else recently.

------
phkahler
So where are they along the project plan to useful fusion energy? Since that
is not the end goal of this project, how far along the project plan for this
device are they?

I'm really well past the phase of being excited about milestones like "record
for a stellarator". Put it in context, show where we are on the plan. Perhaps
it's behind, but still moving forward - that's fine. Confirming things work as
predicted is awesome and tells me they should be moving forward at a good pace
right? So where are they on that gantt chart?

~~~
Semirhage
Nowhere close, but as you rightly stated, that isn’t the goal of this
experimental device. For what it is, which is an exploration of the dynamics
of containing high temperature plasmas, it is a resounding success. What
you’re asking is sort of like someone asking Babbage how close he is to a
Pentium 90. Babbage still did some incredible and foundational things, and it
was still a world away from playing Doom.

There are a lot of issues outstanding for fusion to be a viable power source,
and this reactor is simply exploring the dynamics of one of those issues.
Putting aside hype and desperation, there is no chart yet. For a fusion plant
to work and compete with any other plant, you need it to have good uptime,
relatively low maintenance burdens in terms of downtime and costs, good
output, a viable source of fuel, a fusion cycle that is safe and sustainable,
and more.

As of today the d-t cycle isn’t sustainable because it requires tritium,
produces a lot of energetic neutrons that along with helium will undermine the
reactor. The problem is that more viable fusion cycles occur at significantly
higher temperatures and it’s a struggle to control plasma at d-t temps. The
lack of control both quenches the reaction, and exposes parts of the reactor
to plasma which erodes the material. Neutron bombardment causes the metal to
become brittle, and helium infiltrates and undermines it too. So a reactor
would be down for maintenance a lot, which would make it difficult to work as
an economically viable source of power.

As of today the tritium for the reaction has to be bred in fission reactors.
There are theoretical plans to use a “blanket” impregnated with an isotope of
Lithium to breed tritium within the fusion reactor, but so far no one has
gotten it to sustainably work near necessary levels. As a result a fusion
reactor today would require fission reactors, and it might make sense to ask
why we don’t just stick to the far more mature and efficient fission
technology.

There are lots of other issues that aren’t as big or obvious as what I’ve
described, but ITER and desperation hype aside, there are more unsolved
problems than solved. So where this reactor is concerned, be excited for what
it is away from the context of “fusion any day now!” hype. Appreciate the
slow, but steady progress in the context of incremental research.

If you want clean power in your lifetime, support fission plants.

~~~
Certhas
Mostly agreed, but: "If you want clean power in your lifetime, support fission
plants."

Not anti nuclear or anything, but you really want a large share of wind+solar.
Less hard to handle waste and cheaper. Once we are approaching 80% wind+solar
we can discuss how to best deal with the difficult remaining 20% (load
shifting, expanded transmission grids, storage, CCX and Carbon2Gas gas plants
and nuclear are all options that are possibly going to play a role).

~~~
apendleton
They're only cheap and low-waste if you don't have to worry about storage, and
that needs to be solved well before the 80% point. Battery manufacture is
pretty dirty, and even if the environmental issues were not a concern, it's
not clear that enough raw materials (rare earths, etc.) exist in the world to
move the entire power grid to intermittent sources plus battery storage. And
so far, no alternative storage sources have proven themselves broadly viable
(pumped hydro is probably closest but requires fairly specific climate and
geography).

Personally I'm with Bill Gates on this one: we basically need an innovation
miracle to solve our energy and climate problems, but probably just one, and
it can be in any of four or five different fields (renewables + storage,
fission, fusion, biofuels, carbon capture, etc.). Success in any one of those
spaces is far from guaranteed, so we shouldn't put all our eggs in one basket,
and should be aggressively pursuing all of them in the hopes that at least one
will pan out.

~~~
Certhas
Could you please point me to reputable studies that back up your claim that
storage will be needed before very high penetration?

Even for extremely high carbon reductions (95% on 1990) the best models I've
seen consider transmission lines and sector coupling considerably cheaper. And
these models make very aggressive assumptions on the fall of battery prices.
E.g.:

[https://arxiv.org/pdf/1801.05290.pdf](https://arxiv.org/pdf/1801.05290.pdf)

Edit: The thing to look at is figure 11. on page 16. It gives a policy trade
off. Given political limits on the amount of transmission grid extension (x
axis) what is the cost of the economically optimal mix of technologies (y
axis). Left graph shows sector coupling, right graph shows sector coupling.
The second graph almost completely eliminates the need for battery storage.

Nuclear is not in this mix, partly because this is exploring policy
constraints on transmission capacity in the context of Europe (and nuclear is
pretty much a non-starter politically) but it clearly shows that the idea that
large amounts of battery are inevitable is outdated.

I'll leave you with a quote from the conclusions:

"The All-Flex-Central scenario with optimal transmission costs just 13% more
than today’s system [even when excluding health benefits]"

~~~
apendleton
You're right that arrangements that mostly avoid storage are _possible,_ but
might not be cost efficient in a way that leads to their eventual adoption,
and any mass adoption of renewables at high percentages of overall capacity
requires some kind of major investment beyond the cost of generation itself,
to deal with the intermittency, be it storage or transmission (and the latter
is really only helpful if by "renewables" you mostly mean wind -- the
intermittency of solar is obviously highly correlated over broad geographic
areas). Still, I think the more interesting question isn't "could it be done"
\-- it's pretty clear that it could -- but "could it be done in a manner
that's cost-competitive with non-renewable technologies," and there's pretty
abundant research at this point that shows that any advantages renewables have
in terms of levelized cost of ownership get more than wiped out once these
kinds of investments are factored in; see, e.g.,
[https://www.lazard.com/perspective/levelized-cost-of-
energy-...](https://www.lazard.com/perspective/levelized-cost-of-energy-2017/)
From the executive summary:

> Despite the sustained and growing cost-competitiveness of certain
> Alternative Energy technologies, advanced economies will require diverse
> generation fleets to meet baseload generation needs for the foreseeable
> future

with specific numbers in the actual report.

It's easy enough to focus on Europe or the Americas where the rich have the
comparable luxury of being able to overpay for generation if the political
will is there, but the overwhelming majority of new generation capacity
brought online globally in the next century won't be in these places, it will
be in Asia, Africa, and South America, as these countries work towards
developmental parity with the West. We need to come up with solutions that
aren't just possible, but cheap, and deployable in places that are starting
from basically nothing in terms of modern grid infrastructure, and where
hyper-inefficient diesel generation is currently the norm, to the extent that
electricity is broadly available at all (as is the case in large parts of
Africa in particular today).

Again: this isn't to say that renewables can't work, or that any other
particular technology will or won't be the solution. We just don't know yet,
both in terms of feasibility and economics.

~~~
jnxx
> We need to come up with solutions that aren't just possible, but cheap

Renewable energy sources are already cheaper than traditional nuclear energy,
in many parts of the world already cheaper than fossil sources, and rapidly
getting even cheaper:

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

And at the same time, Westinghouse had to file for chaper 11 bankruptcy
because ... well, nuclear power does not seem to be so economical at all.

As an interesting side note, both nuclear power as well as renewable energy
sources have the cost structure that almost all investments are up-front,
while the relative amount of running costs is very small. Because in a market
system, the marginal cost of production per unit determines the market price,
and the market price is therefore close to zero, both technologies have the
problem that they actually need subsidies and incentives to be created. In
other words, while renewable power sources definitively need incentives,
nuclear power also can't exist without huge subsidies.

~~~
apendleton
> Renewable energy sources are already cheaper than traditional nuclear energy

Again: only when looking at the cost of generation alone. It's more expensive
if you factor in the storage and/or long-distance transmission necessary for
high utilization (even the study I'm responding to says so, though by a
smaller amount than I've seen elsewhere -- ~13%).

> well, nuclear power does not seem to be so economical at all.

Nuclear power isn't economical under the current regulatory environment and
set of political realities. There's no fundamental reason that that need be
the case. More people die from wind and solar per year than nuclear (mostly
installers and technicians falling off of things), and obviously both are
dwarfed by orders of magnitude by coal once externalities are factored in. If
we were as risk-averse with those sources as we are with nuclear, they would
be expensive too. Coupled with the slowness of construction eliminating
economies of scale or effective market competition, and you don't have a great
situation.

~~~
jnxx
I live in Scotland, and was living in Northern Germany before. We _do_ have
high penetration here:

[https://www.businessgreen.com/bg/news/3029756/scottish-
wind-...](https://www.businessgreen.com/bg/news/3029756/scottish-wind-power-
enjoys-record-breaking-start-to-2018)

And it works pretty well. The last power failure I can remember which was in
any way related to wind energy was in 2006:

[https://en.wikipedia.org/wiki/2006_European_blackout](https://en.wikipedia.org/wiki/2006_European_blackout)

(but wind energy was not the primary cause, the main cause was bad planning)

What happens at large scale is that the fluctuations induced by variable wind
speeds smooth out over larger regions. And having a large, interconnected grid
is usually much cheaper than battery storage.

What would also help is diversification. In Scotland, there was a fascinating
project to generate electricity from wave power, the Pelamis wave power
converter. It had working 500 kW installation but was scrapped then.

[https://www.youtube.com/watch?v=JYzocwUfpNg](https://www.youtube.com/watch?v=JYzocwUfpNg)

Fortunately, some Chinese companies seem to have copied the design:

[http://www.dailymail.co.uk/news/article-3832029/Chinese-
wave...](http://www.dailymail.co.uk/news/article-3832029/Chinese-wave-power-
device-suspiciously-similar-Scottish-machine.html)

> If we were as risk-averse with those sources as we are with nuclear, they
> would be expensive too.

A wind power plant blowing up will not cause half of Europe to be contaminated
with huge costs to agriculture, like it happened in 1986. You must also not
forgot the extreme health costs of uranium mining.

------
ckastner
This is fantastic news!

Based on this information, I conclude that nuclear fusion is probably only
about 20 years away.

~~~
adrianN
Can we stop with the "fusion will always be x years away" meme? Fusion is
mostly a number of invested dollars away. A big reason why we don't have
fusion reactors yet is because nobody invests sufficient amounts into the
necessary research. Check this graph
[http://imgur.com/sjH5r](http://imgur.com/sjH5r) from the old Slashdot
interview

[https://hardware.slashdot.org/story/12/04/11/0435231/mit-
fus...](https://hardware.slashdot.org/story/12/04/11/0435231/mit-fusion-
researchers-answer-your-questions?sdsrc=rel)

It's just disrespectful to all the brilliant physicists and engineers who work
on the topic to belittle their efforts like that.

~~~
bischofs
You have to admit that there is something to this meme, It seems like Fusion
suffers from a lack of focus and direction. Ive heard all sorts of horror
stories about physicists and engineers going off on fusion design tangents
that pull funding away from more viable designs as far as energy-in/energy-
out.

I understand that there is a level of experimentation and R&D that is
guaranteed not to generate viable results but at some point you need to trim
the fat, get everyone moving in one direction etc. This grand project has been
going on for over 50 years at this point, It seems like we should at least
have one design that everyone should be focusing on. If they had real, defined
commercial goals (even if they miss the goals) it might be easier to secure
funding because your average politician would see the benefit to them.

I'm not a nuclear engineer so take that all with a grain of salt.

~~~
alexgmcm
It's hard to know what is a 'tangent' and what is the next breakthrough
though.

As they say - if we knew what we were doing it wouldn't be research.

