Research provides reassurance that heat flux will be manageable in ITER

Research led by PPPL provides reassurance that heat flux will be manageable in ITER
Fish-eye view of ITER construction with tokamak site in center. Credit: ITER

A major issue facing ITER, the international tokamak under construction in France that will be the first magnetic fusion device to produce net energy, is whether the crucial divertor plates that will exhaust waste heat from the device can withstand the high heat flux, or load, that will strike them. Alarming projections extrapolated from existing tokamaks suggest that the heat flux could be so narrow and concentrated as to damage the tungsten divertor plates in the seven-story, 23,000 ton tokamak and require frequent and costly repairs. This flux could be comparable to the heat load experienced by spacecraft re-entering Earth's atmosphere.

New findings of an international team led by physicist C.S. Chang of the U.S. Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL) paint a more positive picture. Results of the collaboration, which has spent two years simulating the , indicate that the width could be well within the capacity of the divertor plates to tolerate.

Good news for ITER

"This could be very good news for ITER," Chang said of the findings, published in August in the journal Nuclear Fusion. "This indicates that ITER can produce 10 times more power than it consumes, as planned, without damaging the divertor plates prematurely."

At ITER, spokesperson Laban Coblentz, said the simulations were of great interest and highly relevant to the ITER project. He said ITER would be keen to see experimental benchmarking, performed for example by the Joint European Torus (JET) at the Culham Centre for Fusion Energy in the United Kingdom, to strengthen confidence in the results.

Chang's team used the highly sophisticated XGC1 plasma turbulence computer simulation code developed at PPPL to create the new estimate. The simulation projected a width of 6 millimeters for the heat in ITER when measured in a standardized way among tokamaks, far greater than the less-than 1 millimeter width projected through use of experimental data.

Deriving projections of narrow width from experimental data were researchers at major worldwide facilities. In the United States, these tokamaks were the National Spherical Torus Experiment before its upgrade at PPPL; the Alcator C-Mod facility at MIT, which ceased operations at the end of 2016; and the DIII-D National Fusion Facility that General Atomics operates for the DOE in San Diego.

Widely different conditions

The discrepancy between the experimental projections and simulation predictions, said Chang, stems from the fact that conditions inside ITER will be too different from those in existing tokamaks for the empirical predictions to be valid. Key differences include the behavior of plasma particles within today's machines compared with the expected behavior of particles in ITER. For example, while ions contribute significantly to the heat width in the three U.S. machines, turbulent electrons will play a greater role in ITER, rendering extrapolations unreliable.

Chang's team used basic physics principles, rather than empirical projections based on the data from existing machines, to derive the simulated wider prediction. The team first tested whether the code could predict the heat flux width produced in experiments on the U.S. tokamaks, and found the predictions to be valid.

Researchers then used the code to project the width of the heat flux in an estimated model of ITER edge plasma. The simulation predicted the greater -flux width that will be sustainable within the current ITER design.

Supercomputers enabled simulation

Supercomputers made this simulation possible. Validating the code on the existing tokamaks and producing the findings took some 300 million core hours on Titan and Cori, two of the most powerful U.S. supercomputers, housed at the DOE's Oak Ridge Leadership Computing Facility and the National Energy Research Scientific Computing Center, respectively. A core hour is one processor, or core, running for one hour.


Explore further

Multiscale simulations help predict unruly plasma behavior

More information: C.S. Chang et al, Gyrokinetic projection of the divertor heat-flux width from present tokamaks to ITER, Nuclear Fusion (2017). DOI: 10.1088/1741-4326/aa7efb
Citation: Research provides reassurance that heat flux will be manageable in ITER (2017, September 26) retrieved 19 October 2019 from https://phys.org/news/2017-09-reassurance-flux-iter.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
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Sep 26, 2017
How many decades have we wasted in this quest?? How many tens of $billions?

Meanwhile, my PV system powers my house and car, . . both house and horsepower, and it is CLEAN.

Tell them to get out of their complex computer analyses and look outside at clean, cheap and SIMPLE power.

Sep 26, 2017
Disagree with you on this one, GK. While this is a long, expensive and frustrating road, the payoff is immense. In a world with solar, wind and other sources of green power, I think there will be room/need for central station power not based on fossil, or fission fuel. I think there is need for "compact" high output generation that does not impact large areas of land, especially if fusion gets to the point where it can be used for things like ships and spacecraft. How big a solar/wind array would you need to reliably operates something energy intensive, like a steel mill?? A grid with both distributed green and fission central power seems reasonable to me. I guess we'll see, and the sooner the better!

Sep 26, 2017
ITER, the international tokamak under construction in France that will be the first magnetic fusion device to produce net energy


There a many fusion experimental devices, how could this author possibly state unequivocally ITER will be the first?

Sep 26, 2017
Meanwhile, my PV system powers my house and car, . .


Sounds great, but carbon unit is right, especially regarding spacecraft. Because sunlight drops off according to the inverse square law, if you are ten times further from the sun than Earth is, i.e., 10 AU, the intensity of sunlight drops to 1 percent. It is not hard to see that solar power will never cut it alone for crewed exploration of the outer solar system. A fusion-based propulsion technology would overcome that limitation and even potentially allow us to use materials, e.g., deuterium, that can be found out there to refuel. Most importantly, fusion's potentially high efficiency could help us explore the solar system in person, not just with robots.

Sep 26, 2017
@carbon, I agreed with everything you said except your implication that fusion isn't green:
A grid with both distributed green and fission central power...

Sep 26, 2017
Re: "Results of the collaboration, which has spent two years simulating the heat flux, indicate that the width could be well within the capacity of the divertor plates to tolerate."

So, what you're saying is that you have a simulation. But, didn't you also have simulations each previous time?

Sep 26, 2017
ITER, the international tokamak under construction in France that will be the first magnetic fusion device to produce net energy


There a many fusion experimental devices, how could this author possibly state unequivocally ITER will be the first?

Maybe he's French...?

Sep 26, 2017
A grid with both distributed green and
FUSION
central power seems reasonable to me.

Fixed that for ya...:-)
Altho, I'm pretty sure we all knew it's what you meant...:-)

Sep 26, 2017
Re: "Results of the collaboration, which has spent two years simulating the heat flux, indicate that the width could be well within the capacity of the divertor plates to tolerate."
So, what you're saying is that you have a simulation. But, didn't you also have simulations each previous time?


Years ago is ancient history. We all know about moore's law. Speed rules! Simulations are getting better.
Just wait till they have a quantum computers to do the simulations and quantum computers to design the simulations also. The simulations could be as good as the real thing, at which point they can change the variables to improve their knowledge. Kind of like the movie "War Games" where it plays scenario simulations over and over till it comes up with the cheapest, smallest and most efficient way to build a fusion reactor.
And then we can do simulations of a great many other things to improve those things to. Like human longevity or nootropics etc.
A true brave new world :-)

Sep 26, 2017
The byline on this article says it was written by John Greenwald
The bottom of this article says it was provided by Princeton Plasma Physics Laboratory
What gives?

Sep 27, 2017
This comment has been removed by a moderator.

Sep 27, 2017
'the plasma, like a naughty child, refuses to obey. The reason is either that the plasma is so silly that it does not understand the sophisticated mathematics, or it is that the plasma is so clever that it finds other ways of behaving, ways which the theoreticians were not clever enough to anticipate.


Perhaps it is just physics.

Sep 27, 2017
Gkam, how clean is manufacturing of your PV cells and batteries (I suppose you also have those)?

Sep 27, 2017
The photoelectric effect is horribly inefficient. Solar and wind are worthless for the energy needs coming. If the world is too stupid to fully-adopt nuclear, they need something.

Sep 27, 2017
If the world is too stupid to fully-adopt nuclear


I think the world is mostly rock, therefore it has no nervous system.
Perhaps you need to rephrase your comment more intelligently.

Sep 27, 2017
ITER, the international tokamak under construction in France that will be the first magnetic fusion device to produce net energy

There a many fusion experimental devices, how could this author possibly state unequivocally ITER will be the first?

Maybe you missed the 'net' part.

The photoelectric effect is horribly inefficient.

Really? High efficiency solar cells are hitting the 45% mark (and simulations show that over 50% is possible).
https://phys.org/...ncy.html
That's more efficient than basically anything (save for fusion and fission) - certainly anything fossil fuels have to offer.

Solar and wind are worthless for the energy needs coming

What 'energy needs'? Energy needs are plateauing or even dropping in developed nations (because of increased efficiency in production, everyday items, and emphasis on insulation to reduce waste)

Sep 27, 2017
ITER, the international tokamak under construction in France that will be the first magnetic fusion device to produce net energy


There a many fusion experimental devices, how could this author possibly state unequivocally ITER will be the first?


Because no other machines have even been designed to hit net energy production.

Sep 27, 2017
A grid with both distributed green and
FUSION
central power seems reasonable to me.

Fixed that for ya...:-)
Altho, I'm pretty sure we all knew it's what you meant...:-)
LOL, yeah, I missed that one. I just scanned across it and read fusion.

Sep 27, 2017
The byline on this article says it was written by John Greenwald
The bottom of this article says it was provided by Princeton Plasma Physics Laboratory
What gives?

He works there.

On Earth.

Sep 27, 2017
Because no other machines have even been designed to hit net energy production.


That still does not mean that ITER will hit net energy production first.
ITER has a long way to go. Some of the others are comparatively smaller, so their turnaround time is much shorter.
There is a LOT of money being invested in those smaller ones because some of the really big, sharp, savvy investors are not so sure ITER will get there first,
At this point it's a horse race and no really intelligent people will say their horse will absolutely win.

Sep 28, 2017
rederkis, I could not agree with you more. ITER appears to be a trojan horse. ITER folks CORRECTLY emphasize the immense potential importance of ITER only to suck up funding, then refuse to follow through in any scientifically meaningful way. ITER should be advancing plasma science right now, not sucking up funds that could be going to more promising recent approaches. How ridiculous is it that their design using old niobium-tin alloy superconductors will have been surpassed by at least one and possibly many generations of better designs by the time it finally starts using deuterium-tritium plasma no earlier than 2035?

Two years ago, MIT unveiled a design using rare-earth barium copper oxide (REBCO) superconducting tapes that is already far superior to ITER. Here is the key . . . volumetric fusion power density varies with the FOURTH power of the magnetic field strength. So a near doubling of the magnetic field yields an order of magnitude improvement in power.

Sep 28, 2017
Two years ago, MIT unveiled a design using rare-earth barium copper oxide (REBCO) superconducting tapes that is already far superior to ITER. Here is the key . . . volumetric fusion power density varies with the FOURTH power of the magnetic field strength. So a near doubling of the magnetic field yields an order of magnitude improvement in power.


Plus higher tesla ratings significantly reduces necessary size of reactor.
But as it was pointed out MIT's SPARK and ARC are not meant to produce net energy but it's a major step in right direction.
Personally I feel that using the quantum computer simulations will change everything, including perhaps showing us how to produce cold fusion(Unlike what is being tried now :-)

Sep 28, 2017
I sincerely hope quantum computing will come to the rescue. We need this technology now, not a century from now.

For the record, in so many ways I would really like to cut the folks at ITER a break because I believe in what they are trying to do, but I just can't get past their unbelievable schedule slips. After the participant nations put a signed agreement in place to move forward in 2006, I am dumbfounded that first plasma is now scheduled for December 2025 and deuterium-tritium plasma in 2035. How can they justify nearly THIRTY (30) years from agreement to completion! They tell us the world needs fusion then they waste entire decades!

https://www.iter....e/-/2482


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