When Will Fusion Work? Insights from ITER and Expert Opinions

[rogerk8]

Hi!

I am just asking a question a friend of mine asked me: "When will fusion work?"

I personly think it is not a question of if as much a question of when.

I am a little bit lazy here but I have read the ITER information a while ago and I think they said very confidently that this new Tokamak will give more energy out than is put in.

It would be very nice if someone competent would care to comment on the above.

Roger

 

[mfb]

I am a little bit lazy here but I have read the ITER information a while ago and I think they said very confidently that this new Tokamak will give more energy out than is put in.

That is expected, but ITER won't produce electricity. The planned DEMO, to be built based on ITER results, might demonstrate the viability of a power plant, including estimates of the costs.

 

[Drakkith]

When will fusion work? Without a sudden breakthrough, probably about 50 years from now.

 

[the_wolfman]

"When will fusion work?"

As a fusion researcher the honest truth is that nobody knows, but unless there are major changes/breakthroughs its not going to be any time soon. There are technological issues, but there are also political and economic issues. Currently some European (Germany) and Asian (China, Korea, Japan) countries are serious about developing fusion as a power technology. They are the ones building the next generation research facilities that are needed to support ITER. IMO it is the future policies of these countries that will likely dictate when fusion will work.

I am a little bit lazy here but I have read the ITER information a while ago and I think they said very confidently that this new Tokamak will give more energy out than is put in.

There is a lot of angst in the US fusion community with regards to ITER. Yes we expect that a tokamak with ITER's parameters to ignite. But the story isn't that simple. We know that ELM's and disruptions are going to be problematic. Both of which have potential to cause major damage. Avoiding or mitigating these events is essential to the success of ITER, and they are major thrusts of research. While there are a number of promising solutions, there are currently no guarantees! There are also serious concerns about first wall materials. The inside of a burning tokamak is an incredibly harsh environment, and there are few if any known materials that can withstand that environment for long periods of time.

The planned DEMO

I just want to stress that there are no plans for DEMO. DEMO is just an idea, and the necessary "objectives" of DEMO differs greatly. For example you mention demonstrating economic competitiveness. I'd argue that as an experimental power plant, DEMO is likely going to have a lower duty cycle. It is also going to be a unique first of a kind facility. Both of these are going to greatly increase its cost of electricity. As a result DEMO is inherently poorly suited to demonstrate the economic feasibility of fusion.

 

[cjl]

When will fusion work? Without a sudden breakthrough, probably about 50 years from now.

Fusion is 50 years away, just like it was 50 years ago...

:tongue:

 

[PAllen]

Fusion is 50 years away, just like it was 50 years ago...

:tongue:

As someone fascinated with controlled fusion from the 1950s (thinking, circa 1960, in elementary school, that laser ignition of lithium deuteride pellets was the way to go - for some reason I was quite confident of this ), my perception is that the time between now and commercial fusion has slowly increased over time. In 25 years, then 30 years, then 40, then 50 ...

 

[rogerk8]

Fusion is 50 years away, just like it was 50 years ago...

:tongue:

What would the world be without pessimists? :)

 

[PAllen]

Of course, in the absence of being in the "Nuclear Engineering" forum, we can give many silly answers to the question "when will fusion work"?

1) It has worked fine for nearly 14 billion years.
2) Man made fusion has worked fine for over 60 years for some (MAD) purposes

 

[PAllen]

Fusion is the ultimate counterexample to those who say that any technological breakthrough comes sooner than expected. This attitude is nothing but a case of selective memory - many times yes, many times no, sometimes with a vengeance.

 

[mfb]

I just want to stress that there are no plans for DEMO. DEMO is just an idea, and the necessary "objectives" of DEMO differs greatly.

Let me rephrase that: it appears on timelines, andthere are estimates how some important parameters would look like.

For example you mention demonstrating economic competitiveness. I'd argue that as an experimental power plant, DEMO is likely going to have a lower duty cycle. It is also going to be a unique first of a kind facility. Both of these are going to greatly increase its cost of electricity. As a result DEMO is inherently poorly suited to demonstrate the economic feasibility of fusion.

I said DEMO should help to do that estimate. I did not say DEMO would be such an estimate itself.

Fusion is 50 years away, just like it was 50 years ago...

:tongue:

50 years ago, scientists planned with more money.
If you cut funding, timelines extend (or stay constant even with scientific progress). That is quite natural.

 

[PAllen]

If you cut funding, timelines extend (or stay constant even with scientific progress). That is quite natural.

I don't think that is very relevant. Many other technologies came sooner than expected despite politics of funding. Further, funding for fusion only decreased after multiple predictions failed. To my mind, predicting future technology you have a range of possibilities:

- something unforeseen makes a challenge much easier
- development goes roughly as guessed
- something unforeseen makes progress harder than expected

Examples of the first are numerous and obvious. I would say rocketry is an example of the second case. Fusion is the clearest example I know of for the third case. True AI is perhaps another, but for that, there never was a consensus of expert opinion. For fusion, it really seemed less difficult 50 years ago than today.

 

[mfb]

I don't doubt that fusion has some unforeseen problems. I just think they are problems that new fusion test reactors can solve, and that we see the same for solved issues in the past.

 

[russ_watters]

Frankly, at this point I wish fusion (and solar and wind and clean coal to lesser extent) would just go away. Hope for these Salvation technologies steals focus, funding and political capital from fission, which is a significantly underutilized Now technology.

 

[mfb]

I like fission, but it has some acceptance problems in many countries.
It is not more dangerous than some other types of electricity production, but it is way easier to induce fears and bad news about it.

 

[rogerk8]

Frankly, at this point I wish fusion (and solar and wind and clean coal to lesser extent) would just go away. Hope for these Salvation technologies steals focus, funding and political capital from fission, which is a significantly underutilized Now technology.

I kind of agree with you here. But fusion would be cleaner and hydrogen is abundant.

As the situation is right now I am actually longing for some politically incorrect power company to claim that they are only supplying fission power.

Roger

 

[cpscdave]

I like fission, but it has some acceptance problems in many countries.
It is not more dangerous than some other types of electricity production, but it is way easier to induce fears and bad news about it.

This is the fallacy of the current enviromental movement. They've blocked construction of new fission plants, and then site 50 year old technology as examples of why we shouldn't be building fission plants. (The same goes with oil pipelines but that's off topic)

I can't remember the chaps name, but I think its telling that one of the most ardent anti-fission activists in the 70's has done an 180 switch and now supports them whole heartly.

 

[rogerk8]

It is a strange thing with these transmutation reactors. They seem to exist but no one talks about them. I wonder why because what they do is that they make hazardous nuclear waste less hazardous by some genious means.

May the lack of discussion come from the fact that things are still and simply radioactive?

Roger

 

[mfb]

This is the fallacy of the current enviromental movement. They've blocked construction of new fission plants, and then site 50 year old technology as examples of why we shouldn't be building fission plants. (The same goes with oil pipelines but that's off topic)

What do you mean with "this"?
Your post is just another argument why nuclear reactors are not as problematic as they are perceived by many.

It is a strange thing with these transmutation reactors. They seem to exist

They do not (yet?).
They would reduce the amount of problematic nuclear waste.

 

[Student100]

I'm mostly surprised that the government took as long as it did here in the US to cease LENR funding.

The Fukushima disaster hasn't helped fission one bit.

I thought 30 years was the standard for when fusion would become viable for net power generation? Has there been any more breakthroughs since the paper on "pockets of impurity" was published? I think that was like three years ago.

 

[rogerk8]

Because I'm a lazy guy and would like to put it on the table, I wonder when ITER will be operational (test-wise, that is).

Roger

 

[etudiant]

Not convinced about the effectiveness of 'transmutation reactors'.
Most nuclear contaminated material has minute amounts of radioactive isotope in a matrix of millions of times more conventional material. Irradiating the lot in order to eliminate one problem risks creating a dozen new ones. So the only place where this might be useful is for reprocessing nuclear fuel, which gets back to breeders and thorium reactors.

 

[mfb]

Because I'm a lazy guy and would like to put it on the table, I wonder when ITER will be operational (test-wise, that is).

"When it's done". See the ITER timeline for current plans, but it is unlikely that they will remain unchanged since ~2020.

@etudiant: A chemical separation of different elements would be the first step. Transmutation mainly burns transactinids (elements heavier than uranium), if you manage to split them they usually give isotopes with better properties (much shorter or much longer lifetime).

 

[etudiant]

"When it's done". See the ITER timeline for current plans, but it is unlikely that they will remain unchanged since ~2020.

@etudiant: A chemical separation of different elements would be the first step. Transmutation mainly burns transactinids (elements heavier than uranium), if you manage to split them they usually give isotopes with better properties (much shorter or much longer lifetime).

Sounds messy to me.
A chemical separation of a mass of seriously radioactive materials will not be cheap or clean.
It is of course feasible, but it also leaves a substantial volume of contaminated spent reagents, plus of course a radioactive separation facility. The LFTR might wind up relatively simpler and cheaper.

 

[mfb]

Handling radioactive material is not so problematic if you don't need humans nearby. The chemical reactions would not lead to additional radioactivity, they would just split the material in parts mainly with short-living isotopes (-> can be stored until the material is decayed), very long-living isotopes (does not produce heat, is easier to store forever) and transactinids -> transmutation.

 

[rogerk8]

Some ITER data:

1) Component Assembly Start: 2014
2) Operational: 2019
3) Temperature: 150 Million Degrees
4) Magnetic Flux Density: 13 Tesla
5) Cooling Temperature: 4 Kelvin (-269 Degrees)

My memory is bad but something was said about pellets which could be injected into the plasma to control ELMs(?) which are a kind of instability which I know from courses has been much of a problem in Tokamaks. These pellets I think where made of pure DT-fuel and thus stabelizis the plasma. There was even a feature that made the trajectory of the pellets to be curved thus intersecting "eruptions" wherever they might occur.

More interesting info: http://www.iter.org/

Roger

 

[mheslep]

Some ITER [STRIKE]data[/STRIKE]:

Goals.

 

[rogerk8]

I do however not understand why they insist on DT-fuel. As far as I understand this kind of fuel requires even higher temperatures than in the core of the sun (ten times higher actually). Another drawback is, while Deuterium is abundant, Tritium is not and will have to be breeded at site with the use of Lithium. Actually the total amount of Tritium on the planet is said to be some 10kg only.

Could anyone explain why ordinary Hydrogen fusion is out of the question?

Roger

 

[mfb]

As far as I understand this kind of fuel requires even higher temperatures than in the core of the sun (ten times higher actually).

The higher temperatures are needed to counter the lower pressure in the reactor, with a higher required power density. The sun has an enormous pressure we cannot even dream to recreate in tokamaks, and at the same time the power density is something like 40W/m³ - way too low for a reactor.
DT is the easiest fuel. All other fuels need even higher temperatures or give way lower reaction rates (usually both at the same time). Sure, you have to create tritium in the reactor, but that is still better than switching the fuel.
DD is a possible option if higher temperatures can be achieved, and PP is several orders of magnitude worse.

 

[mheslep]

Could anyone explain why ordinary Hydrogen fusion is out of the question?

Because the power output of a single cubic meter of solar core material (i.e. ordinary hydrogen, proton-proton fusion) is roughly on par with a toaster oven, some tens or hundreds of Watts - lousy as terrestrial power plant. When the sun's rate of energy release was first calcuated, coal combustion was considered as a possible source because the rate of energy release for mass of coal that size was about right. Such is slow nature of proton-proton fusion. The difference is that the coal would be consummed via combustion in ~10,000 years, the hydrogen via fusion in 5 billion or so.

So yes terrestrial needs DT fusion or close to it.

 

[rogerk8]

The higher temperatures are needed to counter the lower pressure in the reactor, with a higher required power density. The sun has an enormous pressure we cannot even dream to recreate in tokamaks, and at the same time the power density is something like 40W/m³ - way too low for a reactor.
DT is the easiest fuel. All other fuels need even higher temperatures or give way lower reaction rates (usually both at the same time). Sure, you have to create tritium in the reactor, but that is still better than switching the fuel.
DD is a possible option if higher temperatures can be achieved, and PP is several orders of magnitude worse.

Thank you for your reply. Very interesting!

The pressure being

$$p=nkT$$

meaning the volume density, n, of the particles times kT, right?

Interprating this formula and my conclusion from what you have said, the volume density cannot be made high enough so temperature will have to be increased to yield the same pressure as in the sun, right?

Roger

 

[mfb]

Pressure is limited by the magnetic fields - a higher temperature does not allow to increase pressure, so the volume density will go down. As the interaction probability rises quickly with temperature, this still leads to a higher fusion rate (up to roughly 1 billion K for DT).

 

[rogerk8]

Interesting graph!

Let's kind of begin from the beginning. Consider the sun. Protons have somehow bundled up out of nowhere. These ions bundle up more and more until gravity(?) makes them bundle up so tight (in spite of their equal and repelling charge) that fusion to Helium starts and an enormous amount of energy is released. In the same time volume density and thus pressure is kept tight due to gravity and protons being abundant.

How far from the truth am I?

How important is the magnetic fields created by the moving ions (currents) for confining the fusion reactions to the core of the sun?

To me it feels like these currents might not necessarily contribute in a collective manner. The generated magnetic fields might as well be stocastic in direction and thus not be a true inspiration for a Tokamak.

Roger

 

[Drakkith]

The sun, including the core, is electrically neutral. Both ions and electrons exist under very height pressures at the core.

I don't know for certain but I don't believe that magnetic fields play much, if any, role in fusion in the Sun's core.

 

[mfb]

Magnetic fields are not relevant for fusion in the sun.
Pressure due to gravity is dominant. As a really simplified model, you can use Earth as comparison - the lower you are, the higher the pressure.

The magnetic confinement in a tokamak is completely different from the gravitational "confinement" in the sun.

 

[rogerk8]

Thank you for your educational information!

But I'm a stupid guy. When it comes to the birth of a star like our sun I do not understand how gravity can play such an important role.

Protons are positively charged, right?

And equal charge repell, right?

Still protons have obviously bundled up.

Why or more scientifically, how?

It is not enough that protons bundle up, they bundle up so tightly that they start to fuse into Helium.

I don't get this part.

Roger