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Ask MIT Researchers About Fusion Power
Nuclear fusion power is the process of fusing light nuclei together to release energy, and ultimately, to put electricity on the grid. Today, we have six researchers from MIT's Plasma Science and Fusion Center here to answer your questions about fusion power, tokamaks, and public support and funding in the U.S. for this research. The Obama Administration's budget request for fiscal year 2013 is paying for the U.S. share of ITER construction out of the domestic program, starting with the closure of the MIT fusion lab. The interviewees are ready to answer technical and policy questions, so don't be shy! And, as always, please break unrelated questions into separate posts. Read on for information about the researchers who will answer your questions.
Dr. Martin Greenwald is a Senior Scientist and Associate Director of the MIT Plasma Science and Fusion Center. His experimental work focuses on turbulence and transport, density limits, and pellet fueling of magnetically confined plasmas. More recently, Dr. Greenwald has been heavily involved with data management, computation, simulation, networks, and remote collaborations for fusion research.
Professor Ian Hutchinson is interested in plasma control in tokamaks, as well as spatially resolved measurements of the radiated power coming from the plasma. He is the author of the standard fusion textbook Principles of Plasma Diagnostics. Prof. Hutchinson also works on particle-in-cell simulations of astrophysical and laboratory plasmas.
Assistant Professor Anne White researches turbulence phenomena on the Alcator C-Mod tokamak, developing new diagnostics to resolve the small fluctuations which cause energy and particles to leak out. She is the recent recipient of the U.S. Department of Energy Early Career Award.
Professor Dennis Whyte pursues research into plasma–material interactions; that is, the way the hot plasma in a magnetic fusion reactor interacts with the surrounding solid materials walls. His team is also developing novel diagnostics for fusion nuclear science, which is critical as fusion reactors start producing power (and neutrons) over long periods of time.
Nathan Howard and Geoff Olynyk are Ph.D students on the Alcator C-Mod project. Nathan, who is in the final year of his studies, studies turbulent transport phenomena experimentally and through simulation. Geoff, in his fourth year, is working on disruption mitigation, which is a way to quickly and safely shut a tokamak plasma down in a few thousandths of a second.
Professor Ian Hutchinson is interested in plasma control in tokamaks, as well as spatially resolved measurements of the radiated power coming from the plasma. He is the author of the standard fusion textbook Principles of Plasma Diagnostics. Prof. Hutchinson also works on particle-in-cell simulations of astrophysical and laboratory plasmas.
Assistant Professor Anne White researches turbulence phenomena on the Alcator C-Mod tokamak, developing new diagnostics to resolve the small fluctuations which cause energy and particles to leak out. She is the recent recipient of the U.S. Department of Energy Early Career Award.
Professor Dennis Whyte pursues research into plasma–material interactions; that is, the way the hot plasma in a magnetic fusion reactor interacts with the surrounding solid materials walls. His team is also developing novel diagnostics for fusion nuclear science, which is critical as fusion reactors start producing power (and neutrons) over long periods of time.
Nathan Howard and Geoff Olynyk are Ph.D students on the Alcator C-Mod project. Nathan, who is in the final year of his studies, studies turbulent transport phenomena experimentally and through simulation. Geoff, in his fourth year, is working on disruption mitigation, which is a way to quickly and safely shut a tokamak plasma down in a few thousandths of a second.
What do you think of the efforts at http://www.emc2fusion.org/ and http://www.talk-polywell.org/bb/index.php ? They seem to be making real, measurable and open results but the mainstream physics community seems to ignore this progress.
> fusing light nuclei together
Light nuclei? They're just photons.
-- Soruk
Not to raise any fears -- rather out of genuine curiosity -- what happens when the magnetic fields that hold the 90,000,000 degrees Celsius plasma in place fail or loser power on the Alcator C-Mod? I understand it's probably in prototype mode but what sort of safety advantages or disadvantages do Alcator C-Mod designs offer over conventional large scale designs? Does the plasma come into contact with the toroidal super conducting coil? Then what?
My work here is dung.
When will fusion power my house?
As a non-scientist, what are the biggest stumbling blocks for effective fusion reaction? is this truly throwing money down the energy hole, or are there verifiable, measurable benchmarks that lead us from one point to the next. Something like, we got x to work, now we need y, when we get y, we get z and then we get fusion. Is it technology holding us back, politics, or the science?
Life is a great ride, the vehicle doesn't matter
How do you explain the safety/benefits of fusion to a generation of people terrified of nuclear anything?
Are there any good guesstimates on how small a tokamak-based fusion reactor (which produces more energy than consumes) can become? Theoretical limitations on size of the reactor would have obvious implications for pragmatic issues. AFAIK there is very little limitation on how small fission-based reactors can get.
Attitudes make the difference between Space and Time: we want to MAX our temporal, and MIN our spatial extension.
In a lot of areas where research is done on things which don't work yet -- rockets, bridges, transmission systems, etc -- there's a general idea of how things might be able to "scale up" to meet the goals.
Is tokamak fusion really in sight of being commercially viable source of energy? If we need unobtanium to make a commercially viable reactor, wouldn't it make sense to wait until the materials are viable before making even larger tokamaks? What do we learn from making these new, bigger, more expensive reactors?
Or are we trying to build ever-bigger spark gap transmitters as a way to make radio better? Maybe we should look at other schemes?
Or, alternatively, we know of a nice, large, gravity-fed fusion reactor fairly nearby, is the engineering simpler to harness energy from that on a large scale?
-- Erich
Slashdot reader since 1997
As practicing researchers, can you tell us about the health of the pipeline of young researchers coming into the field? Is there a glut of trained physicists at this stage, or is there still a need for trained specialists to enter the field, especially with ITER and follow-on machines coming online in the next couple of decades?
Why aren't IEC reactors based on Farnsworth's designs taken more seriously? From what I understand, IEC's have been more effective at producing fusion, and they are cheap to build. People even build them in the garage. From everything I've read, no one really takes the "fusor" seriously in the fusion science realm, and it's considered a dead line of inquiry. I've never understood why.
Drinking habits can be dangerous. You can choke on the cloth and the nuns will wonder where their clothes are.
Is fusion power going to be feasible in the next 60 years (extrapolating my expected lifespan)?
just skip the Microwave Power Plant in 2020
Do you think a program of the size of the Apollo program could kickstart fusion to general availability? Or would a rather smaller program suffice?
Will patents get in the way of your research?
From the outside fusion research looks like a desperate field that's always struggling with its fundamental research/engineering questions. I know more than most laymen: I know the reactions work, I know the sun is powered by (very slow) fusion, I know fusion reactors have produced at least around 50% return on the electricity put in. Still, it feels like it's possible it'll never work, even knowing that difficult problems take time to solve.
This is the outside view. What does the future of fusion look like when you experts look at it from the inside? Does it look like a gamble? Or does it look more like "just give us proper funding and we'll give you your reactor."?
The late Dr. Bussard of EMC2 [emc2fusion. org] claimed that the fundamental concepts of Tokamak fusion did not provide a platform for cost-effective positive-return power reactors. With the enormous ITER project reactor still not expecting positive return, at what point, if ever, will Tokamak research benefit the power grid?
Given $1Tn, the pick of the best brains in the world to work willingly on the project, a large enough location away from any and all governmental regulation and every facility you could ever need - WHEN WILL IT BE COMMERCIALLY AVAILABLE?
politicians are like babies' nappies: they should both be changed regularly and for the same reasons
Oh and how does it feel to be working on something which you probably will never see come to fruition in your lifetime?
// MD_Update(&m,buf,j);
I understand that long term, we would want fusion, but we face increasing energy problems over the next 50 years and severe energy problems before 2100. Wouldn't it make sense to allocate research and development resources to something that we know works?
Please do not read this sig. Thank you.
But about capturing the power? Are we generating heat that will drive steam turbines?
What schemes to capture and harness the power exist?
intellectual property law is philosophically incoherent. it is your moral duty to ignore it or sabotage it
Do you see any merit in the "dense plasma focus" approach to commercial fusion power production, specifically the work of the Lawrenceville Plasma Physics group?
This has happened many times throughout history. I'm certain the stonemasons who toiled away on Europe's beautiful cathedrals must've worked away, knowing that despite their own obscurity, they were still leaving a legacy.
In 1995, Robert W. Bussard submitted this legislation to all relevant Congressional committees, copying all US plasma physics laboratories.
Needless to say, the legislation wasn't passed.
Do you think the time is right?
Seastead this.
Could you break down the various barriers/bottlenecks to the introduction of commerical fusion?
What are the technical problems in the state of the art, what other factors (political, economic, etc.) do you see at play?
How do you and your labs collaborate with others, and how is technology transferred? Is there much international cooperation?
Are there policy communities (China, India?) that might be more primed for the introduction of fusion technology into their grids than in North America? What would need to happen for North America to start using fusion?
I have many more questions, but those are the ones that popped into my head first. This is such a great opportunity -thank-you for taking the time today!
Is the ITER project good science?
Or, is it a politically motivated, pork laden boondoggle?
Is the NIF approach even plausibly capable of generating electricity in a useful way, or is it purely a research platform / smokescreen for nuclear weapons research?
and even ignoring all questions of whether they can generate net useful, saleable electricity... how likely do you feel that descendants of tokamaks like ITER are to produce economically viable electricity (including capital cost amortization), given their large scaling requirements, and on what sort of timeframe? What about inertial confinement alternatives based on the HiPER approach? As an ousider, it seems to me that the HiPER concept can be scaled down much more, and hence looks more attractive as a generation method.
Teach me to love you, you squishy poet from beyond the stars!
So I'm not a physicist (software guy) but I've taken a few physics classes. At an early age I found a tattered copy of George Gamow's One Two Three . . . Infinity which, although incorrect in some parts (I guess that's why they revised it and that's why 'speculations' was in the title), was perfectly written for my then fifth grade mind. It set me on a path toward science and a few weeks ago I saw the same 1960s Viking Press edition and flipped through it noticing what was slightly off and remembering it. I've since grown to love other obvious books like Hawking, Penrose, Hofstadter, etc.
So, quite simply, what are your favorite books for all minds young and old? Also, can you annotate which are written for the layman's entry into the given field and which are written to encompass the field for the researcher? I find that some books start off with the jargon so strong and the references and footnotes so thick that you start to have to reread every paragraph as they're clearly condensing entire historic papers into lengthy sentences. Any fiction books worthy of influencing your work and desires?
My work here is dung.
There are many potential routes to economic fusion. Assuming each of these concepts were funded at ITER levels, how would you rank the potential for economic fusion (cost competitive with nuclear) coming from each of the following concepts within the next 25-30 years:
1/ Field Reversed Configuration - eg Helion Energy, Tri Alpha
2/ Electrostatic Confinement - eg Polywell/EMC2
3/ Magnetised Target Fusion - eg General Fusion
4/ Laser Inertial Confinement - eg NIF, HiPER
5/ Heavy Ion Inertial Confinement - eg Fusion Power Corporation
6/ Tokamaks - eg ITER, DEMO
7/ Stellarator - eg Wendelstein 7-X
8/ Levitated Dipole - eg MIT LDX
How do you extract the heat once you are successful in fusion? Is there a safe zone where it is just right to run water to convert to steam? With fusion running so hot and containment being such an issue it makes me think that extracting the energy could also be a fair challenge.
If the president came to you and said, "We have a national emergency. We need this to become a viable form of energy as soon as possible. You have the entire resources of the nation available. I will use my executive powers to make it happen. Whatever resources, funding and people you need..." What kinds of things would you ask for? How long with the entire backing of a nation and the political will to make it happen would it take?
Focus Fusion Society http://focusfusion.org/ is posting research on their project to do aneutronic e.g. Proton Boron (pB11) fusion. The concept sounds great, and as an engineer several parts of their design such as direct extraction of electric power are elegant. Is this credible research or pie-in-the-sky? I have not seen much mention in mainstream fusion research.
Sorry to tell you, but the whole He-3 story is a bunch of crap.Neither is He-3 rare, as it is absolutely no problem to make Tritium out of Lithium - you just need to wait 11 years for half the tritium to turn into He-3.
That said, D-He-3 fusion is as hard to achieve as D-D and certainly much harder than D-T fusion. Worse yet, in D-He3 fusion there is a parasitic D-D fusion process that is actually favoured (by nature) over D-He-3. The whole thing is just irrelevant and a huge strawman.
Making fusion power with a massive laser and a tiny bit of deuterium, is what's holding them back, it's rediculous! How about speeding a matter stream of deuterium atoms around a toroid, in a vacuum using superconductive "pinch points" around the circumference? it would set up tiny shockwaves of very high temperature and pressure. As the system is refined the matter stream could become self propelling, sacrificing only a very small percentage of deuterium atoms per cycle. And the potential power generation could be accomplished not through heat, but by using the spinning matter stream as the armature (rotating center) of a generator/alternator.
Really!
I killed da wabbit -Elmer Fudd
Well, one of the major arguments for fusion research is that fission is dangerous and dirty. If we can have clean and safe fission, there absolutely no reason to pursue the fusion pipe dream.
The most important item in the economic equation of a nuclear plant are the capital costs. If we already established fusion needs to be big in order to work, probably much bigger than existing fission plants, then we should stop spending money on large experimental fusion reactors - it is not a solution in it's current form, not if fusion can solve the same problem today.
What is your opinion of General Fusion's (www.generalfusion.com) approach to a fusion reactor design?
$-15 trillion
Fusion is one of those technologies that is always '50 years away', even 50 years ago, maybe even 50 years from now. So, looking at what's actually happened recently:
What do we actually know now that we didn't know 10-15 years ago that gives support to the notion that we're making progress? Or, what are the 'big' things we know now?
Similarly, what are the things we still don't know that we could reasonably expect to find answers for in the next 10-15 years?
I'm assuming it's not that we've figured it all out and it's just a matter of engineering a working prototype.
The byproduct of fusion is Helium? Or is it some other atomic number they are shooting for now (boron?) Anyway, if the plan is to make this a drop-in replacement for coal and natural-gas burners, then how will you keep the unit up and running if its filling up with waste prodcuts. Does it have to be taken down intermitantly? Then what is the startup-time / power requirements / redundancy requirements of a fusion reactor that has to be restarted every 10 days.
ITER/Tokamak has been around for a long time with, to say the least, disappointing results in the long haul.
At some point, practical planning would say that a portion of the money -- even a very small portion -- being spent on ITER projects should be redirected to make sure that the pre-occupation with ITER isn't starving other options that may turn out to be better ideas. It's often been the outliers that succeed even in technology areas where lots of attention and money have been spent on some "standard" solution.
I'm not against pure science but in this situation I'm likely to appear so to some: it's annoying to me that ITER, the long term "solution of the future and always will be" is getting so much money that other options are being starved out. Am I completely out to lunch for some reason?
Still hoping for Gentle Treatment...
Given that solar energy is so plentiful, and that it will likely be widely available in the time frame that fusion power will be available, would it make more sense to apply the expertise of scientists into using fusion for spacecraft propulsion, which is an application that absolutely requires concentrated and compact energy? It could be a game-changer for travel within our solar system.
In addition, could the techniques used for fusion (both magnetic and inertial confinement) be applied to fission propulsion, for compressing fissile pellets to critical density? And would that be more within reach of current technology than the very high temperature and pressure needed for fusion? Why is no one researching that? It would literally open up the solar system for us.
What is the best estimate of the operating size of tokomak power plant? How many do we need to convert the US away from coal & gas power plants while switching to electric cars? What is the answer if we look at 100-year projections for population, energy usage patterns, and density? Will a tokamak-based power grid be more or less useful in parts of the world with different needs, like Europe, Japan, India, or China?
I didn't take it that way.
Like the OP said this is much like the Xprize series of challenges and rewards. Most of the teams and companies competing for those prizes are spending considerably more than the prize money to try and win. The prize is just a PR trophy and a bit of funding aid.
I wouldn't advocate for a system like that being the sole source of federal dollars for fusion research. But there isn't any good reason to not consider adding it to what is already out there.
And as others have said there are a number of Material Science problems with Fusion that we need to work out before it becomes a viable power source. Setting goals/milestones and prizes for achieving those goals would only help the entire project along. At least so long as they don't kill the budgetting for the big research projects.
As someone working in the fusion field, I don't see much infighting, at least with in the magnetic confinement portion. The tokamak people I know don't seem to spend much, if any time, commenting on other designs unless asked about them, and many of the non-tokamak magnetic confinement people don't say much about tokamaks other than they are expensive. There is plenty of sharing and cross-pollination of ideas at conferences between these groups.
There is less talk between magnetic confinement and inertial confinement people, although there is less overlap in equipment and regimes of the experiments. I still see some talk between computer people working with models for both, where there is more overlap.
The polywell people seem to be keeping pretty low key about things, so I think most other researchers in the field don't even know of them. I've bumped into one of their researchers at a conference, but it was out of luck that I recognized the company name on his name tag, and he still didn't talk about their work when asked and wasn't present anything at the conference.
A lot of researchers see stuff like eCat as a fraud, although that is not specific to fusion researchers. It is not surprising more fringe stuff spends more time complaining about mainstream work, although I've found that many people that spend a large time complaining/attacking because they don't have much good to say about their own work. If they wanted to talk about the science of what they do instead of just complaining, they can present at a conference. Considering some of the crackpot presentations I've seen, as long as you pay the attendance fee and are roughly on topic, you're let in.
tl;dr: I haven't seen much infighting. I've seen a lot of collaboration, and at worse ignoring something that seems irrelevant by those in the field, and most attacks/complains by those that are on the outside.
I think fusion reactors scale somewhere like r^4 in terms of Q value. As size increases, confinement time increases, and given the temperature and pressure gradients that can be sustained, the core temperature and pressure can increase.
I can't prove that it's r^4, but I'm sure I remember it being approximately r^4 or maybe r^3 (or somewhere between the 2).
With regards D-D/D-T, when tokamaks such as JET, MAST, ITER and the like run with deuterium, their aim isn't to allow fusion. So a typical deuterium Q value would be 0 or very close to 0.
The reason is that getting deuterium and tritium to fuse isn't the difficulty - so it's not something they have much need to practise. Working in a purely deuterium mode provides the same plasma physics challenges - but without the added difficulty of using tritium (for example, once a tokamak has had tritium in it, human access to the machine is very strictly limited).
With all that's learnt using deuterium and tritium, if a machine such as JET goes for a D-T campaign as it did in 1997, and another campaign was considered recently, then it gives a data point to show performance, proves that progress has been made, and may be useful if they were interested in studying ash (helium) in the plasma.
Studying effects of neutrons is usually done elsewhere - leaving a sample in a source of neutrons for long periods of time (such as in a fission reactor), although a Component Testing Facility is planned in the longer term to expose components to high energy neutrons (14MeV is much higher energy than neutrons in fission).
So not a huge amount is to be gained by running D-T regularly.
Hello, This is Nathan. Thanks for the question regarding the computational methods used in plasma physics/tokamak turbulence simulation. Let me try to answer your question. So my work actually focuses on turbulent transport model validation (the comparison of experimental measurement with computational models) in the core of tokamak plasmas. Fundamentally the difficultly with plasma simulation comes down to the fact that we have a large number of particles (~1x10^20 m^-3) which due to the long range nature of the electromagnetic force, affect the movement of every other particle in the plasma, at every point in time and operate on a wide range of time and spatial scales. Now there are some simplifications to that statement but I wont go into those here. In theory, the Newton-Maxwell set of equations, that is the combination of Newton's laws with Maxwell's equations can give you a complete description of all phenomenmom in the plasma. However, given the large number of particles and the long range nature of the forces involved, this problem is computationally intractable. The first step of simplification is taking a statistical approach to describing the particles in the plasma, that is, describing each population with a distribution function and tracking the evolution of the distribution function. This set of equations is known as the Maxwell-Boltzmann set of equations. However, this is a 6-D set of equations and we require some more simplifcation. To do this we basically elminate the motion of very fast time scales from this set of equations and say we are look at spatial scales which are relevant for microturbulence which drives the transport of heat, particles, etc. in the plasma. The resulting equation is called the gyrokinetic equation and it is thought to contain sufficient physics to simulation the microturbulence which is present in pretty much all plasmas. This is the cutting edge model for turbulence simulation in tokamaks. In these simulations you can see the development of turbulent eddies and structures which result in the transport of heat and particles out of the system on a time scale much shorter than that from purely collisions. Now, as you correctly noted, measurements in high temperature plasmas are indeed quite difficult to make and it is only in the last 10 years that both the models and the measurements have become accurate enough to make any meaningful comparision between the two. In other words, we are just now to the point where we can validate these models through comparison with experiment. To make things more difficult, the temperature profiles in plasmas are often observed to be "stiff". This means that the normalized gradients of these quantities are not easily changed. This arises from the fact that the plasma microturbulence is driven by free energy in the temperature and density gradients. As a result, if the gradient increases, the level of turbulence in the plasma does as well and this results in larger eddies and therefore larger loss of particles and energy from the system. This loss of energy tends to flatten the profiles and reduce the gradient. Therefore there is a critical value at which the turbulence is found to "turn on" and there is a profile shape which the plasma tends to relax to. This makes simulation difficult because it increases the sensitivity of the predicited heat/particle flux to the background plasma gradients. Since the gradients are derivatives of quantities which we measure, they are much more difficult to determine with great accuracy. My own work involves assessing the experimental error in many of the quantities that are driving plasma turbulence. With a proper assessment of the uncertainity in the measurement, I am able to deduce the sensitivity of the model's predictions to the uncertainity in the measurement and make a more meaningful statement of the model's ability to simulate experiment. I am sorry if that was a bit too rambling, but hopefully I at least partially answered your question. If you are interes