Nuclear Physics
Nuclear fusion. Credit: Lancaster University

Physics, Science

Nuclear Fusion Power Closer to Reality Say Two Separate Teams

28 Jan , 2010 by

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For years, scientists have been trying to replicate the type of nuclear fusion that occurs naturally in stars in laboratories here on Earth in order to develop a clean and almost limitless source of energy. This week, two different research teams report significant headway in achieving inertial fusion ignition—a strategy to heat and compress a fuel that might allow scientists to harness the intense energy of nuclear fusion. One team used a massive laser system to test the possibility of heating heavy hydrogen atoms to ignite. The second team used a giant levitating magnet to bring matter to extremely high densities — a necessary step for nuclear fusion.

Unlike nuclear fission, which tears apart atoms to release energy and highly radioactive by-products, fusion involves putting immense pressure, or “squeezing” two heavy hydrogen atoms, called deuterium and tritium together so they fuse. This produces harmless helium and vast amounts of energy.

Recent experiments at the National Ignition Facility in Livermore, California used a massive laser system the size of three football fields. Siegfried Glenzer and his team aimed 192 intense laser beams at a small capsule—the size needed to store a mixture of deuterium and tritium, which upon implosion, can trigger burning fusion plasmas and an outpouring of usable energy. The researchers heated the capsule to 3.3 million Kelvin, and in doing so, paved the way for the next big step: igniting and imploding a fuel-filled capsule.

In a second report released earlier this week, researchers used a Levitated Dipole Experiment, or LDX, and suspended a giant donut-shaped magnet weighing about a half a ton in midair using an electromagnetic field. The researchers used the magnet to control the motion of an extremely hot gas of charged particles, called a plasma, contained within its outer chamber.

The donut magnet creates a turbulence called “pinching” that causes the plasma to condense, instead of spreading out, which usually happens with turbulence. This is the first time the “pinching” has been created in a laboratory. It has been seen in plasma in the magnetic fields of Earth and Jupiter.
A much bigger ma LDX would have to be built to reach the density levels needed for fusion, the scientists said.

Paper: Symmetric Inertial Confinement Fusion Implosions at Ultra-High Laser Energies

Sources: Science Magazine, LiveScience

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Nancy Atkinson is currently Universe Today's Contributing Editor. Previously she served as UT's Senior Editor and lead writer, and has worked with Astronomy Cast and 365 Days of Astronomy. Nancy is also a NASA/JPL Solar System Ambassador.



31 Responses

  1. Thameron says:

    “a clean and almost limitless..”

    Almost limitless? Maybe. Clean? Not as much as people think. You see that neutron up there in that drawing? Where do you suppose it’s going? One possible place it might be going is to collide with the nucleus of another atom and making it radioactive. Now I am no engineer so I don’t know what materials they are thinking of making these fusion reactors out of, but they have to make them out of something and if you expose a material to a strong neutron flux long enough it will become activated i.e. fusion reactors will produce nuclear waste. Probably not as much as fission reactors, but not none. So if producing less nuclear waste than a fission reactor fits the definition of ‘clean’ then yeah they’re clean as we shall all discover in ten years.

  2. Vedic says:

    Yes, from what I understand leaving the ‘spare’ neutron is still going to leave radioactive waste…

    Has anyone heard know how ‘focus fusion’ is coming along?

  3. Manu says:

    In a tokamak design like Iter, the neutrons will help in-situ production of tritium, in two ways: absorption by a deuterium nucleus; and reaction with lithium coating of the plasma chamber.
    http://en.wikipedia.org/wiki/ITER#Reactor_overview
    (see more detail on the French page)

    This might be used too in a pinch machine, but I don’t see how it could be done with inertial confinement.

    All neutrons wouldn’t probably be absorbed, leading to irradiation of chamber material. This is not to be shrugged off, but it’s almost nothing in comparison with fission reactors. The spent fuel from these is a bigger problem by several orders of magnitude.

  4. Surak says:

    My ignorant understand is that the radioactive waste from these fusion reactions generally has a much shorter half life than those of fission.

  5. Dark Gnat says:

    Yes, we get more radiation from the Sun and cosmic sources than what a Fusion reacotr would produce.

    Fusion Power Plants would have the greatest impact on reducing carbon emissions and reliance on oil from unfriendly nations.

  6. solrey says:

    The Dense Plasma Focus is another method for achieving fusion. The progress on focus fusion appears to be going well, Vedic.

    The donut magnet creates a turbulence called “pinching” that causes the plasma to condense, instead of spreading out, which usually happens with turbulence. This is the first time the “pinching” has been created in a laboratory. It has been seen in plasma in the magnetic fields of Earth and Jupiter.

    Actually, the plasma pinch has been created in laboratory experiments for decades.
    Even the filaments in a novelty plasma ball are the result of the pinch effect.

    The first creation of a z-pinch in the laboratory may have occurred in 1790 in Holland when Martinus van Marum created an explosion by discharging 100 Leyden jars into a wire.

    Pinches occur naturally in electrical discharges such as lightning bolts, the aurora, current sheets, and solar flares. They are also produced in the laboratory, primarily for research into fusion power, but also by hobbyists in crushing aluminum cans.

    Pinches are created in the laboratory in equipment related to nuclear fusion, such as the Z-pinch machine and high-energy physics, such as the dense plasma focus. Pinches may also become unstable, and generate radiation across the electromagnetic spectrum, including radio waves, x-rays and gamma rays, and also neutrons and synchrotron radiation. Types of pinches, that may differ in geometry and operating forces, include the Cylindrical pinch, Inverse pinch, Orthogonal pinch effect, Reversed field pinch, Sheet pinch, Screw pinch (also called stabilized z-pinch, or ?-z pinch), Theta pinch (or thetatron), Toroidal pinch, Ware pinch and Z-pinch.

    Pinches are used to generate X-rays, and the intense magnetic fields generated are used in electromagnetic forming of metals (they have been demonstrated in crushing aluminium soft drinks cans). They have applications to particle beams including particle beam weapons, and astrophysics.

    peace,
    Tim

  7. Torbjorn Larsson OM says:

    Well, LDX with its large plasma volume doesn’t sound like an “inertial fusion ignition” experiment. AFAIU it is a tokamak competitor.

    I can’t really get excited about inertial fusion reports since I learned that they have to overcome a fundamental instability, the e Rayleigh–Taylor instability of interstellar clouds and weather inversions. Before they report doing that, it’s a dud.

    if you expose a material to a strong neutron flux long enough it will become activated i.e. fusion reactors will produce nuclear waste

    Yes, that is what they will rely on to produce the needed tritium (which is radioactive), until and if they can get the cleaner deuterium-deuterium reaction going.

    While there’s no beef that this is a major problem for the technology, since the project plans incorporates parallel studies on it, fusion is indeed comparably clean AFAIU and no problem for society as such.

    First, the amount of radioactivity generated and handled is order of magnitudes cleaner than the mining & activation from fission technology. IIRC something like 3-4 orders of magnitude less.

    If fission plants release far less radioactivity to the population than the mining & burn from coal plants already today (IIRC again a factor of several orders of magnitude less), surely fusion plants will be even cleaner!

    Second, the activated products are short- and medium term. For example, tritium has a half-life of 4.5 days compared to fission waste U-235 0.7 Gy or fission fuel U-238 4.5 Gy.

    At a guess, the waste and plant material will have to be curated for some decades as compared to 10s of thousands of years (for waste) in current fission technology. That is on the order of the plant lifetime itself, so it is much more manageable.

    as we shall all discover in ten years.

    Try 60-70 years, if current plans of a first industrial power plant prototype in 40-50 years will come true.

  8. Thameron says:

    The spent fuel obviously will not be a problem as it is with fission plants, but there will still be activation products to deal with. The vessels of conventional fission plants become very radioactive due to their neutron exposure and need to be disposed of carefully. Materials which can withstand the necessary pressures and temperatures to hold in a fusion reaction are probably somewhat constrained so they may not be able to use something more resistant to neutron activation.

    My point though is that fusion energy will not be ‘clean’ in the sense that solar energy is clean i.e. producing no waste except what was necessary to make it.

  9. Thameron says:

    Torbjorn –

    “For example, tritium has a half-life of 4.5 days”

    No, actually the half life of Tritium is 12.33 years. I am not sure where you got that 4.5 day figure. Tritium getting into the water (not to mention the people) is a problem that will certainly need to be addressed.

    My quote about the 10 years was facetious, because fusion power was always 10 years away. In truth I have no idea when or if humans will get that technology to work. As with Mars it may well be not in my lifetime.

    I’d love nothing more than to have us master it and put it on our interplanetary shuttles. Really I would, but I do wish they’d stop billing it as ‘clean’.

  10. doomfistinc says:

    Yeah, just forget about it. The waste products aren’t rainbows and butterflies, so we shouldn’t do it.

    It is still magnitudes cleaner than anything except solar that we have access to. It isn’t like there are going to be millions of tons of garbage left over.

    It IS clean. If people can label new ways to use coal as “clean”, fusion is CLEANERIFFIC^100

  11. clatonium says:

    Almost limitless? Maybe. Clean? Not as much as people think. You see that neutron up there in that drawing? Where do you suppose it’s going? One possible place it might be going is to collide with the nucleus of another atom and making it radioactive.

    I hear boron is an excellent neutron absorbent material. In a fission reactor its a poison, in this case it would reduce radioactive byproducts.

  12. Hon. Salacious B. Crumb says:

    clatonium said;

    “Almost limitless? Maybe. Clean? Not as much as people think. You see that neutron up there in that drawing? Where do you suppose it’s going? One possible place it might be going is to collide with the nucleus of another atom and making it radioactive.
    I hear boron is an excellent neutron absorbent material. In a fission reactor its a poison, in this case it would reduce radioactive byproducts.’

    What rubbish. Unsubstantiated fear of radioactivity by fusion is a nonsense. All of the radiation is contained in the reactor itself, and none will be dangerous to the environment. (unlike fission)
    Most of the radiation is caused by the gamma rays from the fusion reaction.
    Nonetheless, the metal of the reactor will become radioactive to some extent and may have to be replaced from time to time. This is far easier to dispose of than the liquid ‘sludge’ from fission reactors and the radioactive by-products that last for aeons.
    Fusion is a far more sensible clan and safer proposition.

  13. Lawrence B. Crowell says:

    Yeah that neutron is a problem in more ways than one. About 80% of the energy from this reaction is carried off by the neutron. Since the particle is neutral it is not entirely easy to get that energy. You can put heavy water around the reaction chamber and let neutrons thermalize the water. But this is an inefficient process.

    I spent considerable effort about 10 years ago in getting an alternative fusion process considered. The reaction involves lithium. The reactions are the following

    Li^7 + p –> (Be^8)^* –> 2He^4

    or

    Li^6 + D –> (Be^8)^* –> 2He^4,

    where (Be^8)^* is unstable and decays into alpha particles which are charged and their energy extracted by magneto-hydrodynamic methods. There is no thermalizing of water, and their energy can be directly converted to a current by induction.

    The other advantage is that the proton or deuterons are directed in a beam to a lithium foil. There is no need for energy intensive plasmas or inertial confinement methods. The beam just raster scans the lithium foil and the charged daughter products emerge from the back and by MHD produce a current directly.

    LC

  14. Another interesting Fusion approach is General Fusion – http://www.generalfusion.com/t5_general_fusion.php

    The idea is completely out of left field, but after it settles down in your brain it is actually pretty sensible. loud, but sensible.

    LC – I’ve heard about Li fusion a bit before, I’d love to hear more.

  15. Hon. Salacious B. Crumb says:

    The best thing about lithium fusion is it might help with the availability of commercial helium !!

  16. DrFlimmer says:

    But, unlike Hydrogen and its isotopes, Lithium is quite less abundant. This is a massive problem!

    Btw: Fusion plants are always 50 years away from now… whenever “now” is. Hopefully this doesn’t go on forever 😉 .

    Indeed, fusion would solve almost every problem, we face today. Hopefully we achieve it, before it’s too late!

    (Hm. Shall I, or shall I not? Ah, what the heck:
    “Pinched plasma” would not really work to get fusion. Such pinches are highly unstable. They can actually squeeze the plasma, but only to split and cut it. “Sausage instability” – as a keyword. I don’t think this would work for fusion. You need a stable plasma – instabilities are the things you want to get rid of (which is VERY difficult, and one major reason why we have not achieved fusion until now…))

  17. Lawrence B. Crowell says:

    Lithium is actually rather abundant, though not as abundant as heavy water. In fact it is a component of metal ions in sea water.

    The D-T cycle energetically is

    D + T –> He^4(@ 3.5MeV) + n(@ 14.1 MeV)

    while a lithium cycle woiuld be

    Li^6 + D –> (Be^8)^* –> 2He^4(@ 22.4 MeV)

    The input energy of the D+T cycle is about 1MeV and for the Li cycle this is 2-3 times as much. In the Li cycle the energy output per nucleon mass is half that of the D-T cycle, making it appear less attractive. So from one perspective the Li cycle is less effective, but the energy output is not in an electrically neutral neutron and this is a huge advantage!

    Another advantage is that there is no need to super-heat or shock pressure lithium, so the input energy does not have lots of thermal-entropy losses. The accelerator could be a modest accelerator with the energy scale comparable to the LAMPF which with a quadrupole arrangement raster scans a lithium foil and then down stream there is an MDH system that converts the high energy flux of charged alpha particles into electric current energy directly. So the energy output disadvantages of a Li cycle on the nuclear physics level are more than made up for by the thermodynamic and engineering advantages.

    There has been a proposal for a boron cycle as well. The “culture” though is pretty much stuck on the D-T cycle, in part because huge facilities for deuterium and tritium production exist for the production of nuclear weaponry.

    LC

  18. Richard Kirk says:

    I have had a quick look at the General Fusion site. I would have thought a converging shockwave would have to be amazingly symmetric to converge successfully. A real shock wave would surely suffer from Rayleigh-Taylor instabilities.

    I was more convinced by the Bussard “PolyWell” proposal put to Google. That, and Bussard was a cool guy.

    Lawrence’s HMD generator is neat. It always seems a shame to generate even fission energy, and then just use it to heat a steam engine. Much nicer if we can get some of the energy out directly.

    As for regular fusion – the gamma and the neutron are both very penetrating radiations. I worry that it may not produce regular waste, but the entire plant will have radiation daughter products to depths of 10 cms if it is clad in low-Z material. However, you can clad it in a few mm of depleted uranium, which will give off several times more energy, and we already have the technology for reprocessing the products. Sounds handy, until you realize that what we have built is a really expensive fast breeder reactor, with a really expensive bit in the middle instead of making neutrons the regular way.

    I wanted to try and make fusion using a hollowed exploding bridge wire. As the surface flies off, this should generate a huge inward-going shock-wave. The convergence ratio is much smaller so the R-T instabilities should not bite so much.

  19. Aodhhan says:

    Something so simple, made so complex.

    It boils down to making the most energy with as little fuel as possible.

    Every solution has waste, and some have kewl ways of dealing with it.

    LBC….
    You’ll soon find out Li-6 is being tossed out in lieu of Li-7. While both are stable, an exothermic reaction typically isn’t something most people want to deal with at a large scale. Unless you’re building bombs. :)

    …also your Li-6 equation has one too many arrows 😉
    Should be: reactants –> products + energy

  20. gopher65 says:

    @Thameron:

    Whatever gave you the idea that PV solar power is clean? Who told you that? It isn’t.

    The manufacture of all current, proposed, and even imagined solar panels produces ENORMOUS amounts of pollution per watt. And do you think those solar panels last forever? They don’t. Once they reach the end of their lives, you strip out a few key ingredients for (expensive) recycling, and then toss the rest in the trash heap. Because solar is such an un-dense power source, that means a freaking lot of toxic waste (you can’t just toss those panels in a city dump, any more than you can toss a motherboard or a CRT in there).

    If the world was fully solar powered we’d all be living in domes to protect us from the poisoned world outside. So please, stop spreading that biased garbage about how solar is going to save us all. It won’t.

    If you’re looking for the cleaner (and cheaper:P) power, wind and geothermal are probably the best options. If you’re looking for the most versatile form of (future;)) power, fusion is the best. Personally I’d guess we’ll use some mixture of the three, with other power sources (including PV solar) as a tiny, situationally specific, part of our energy solution.

  21. Lawrence B. Crowell says:

    Aodhhan, the additional arrow is to show the unstanble intermediate beryllium.

    As for solar panels, the next step is with dyes, whch are printed on a sheet. Further, I think that graphene, a 2-dim layer of hexagonal carbon. with different P and N dopants will also become a solar cell of the future. The future of solar cells is not the hard silicon wafer we have now, but solar material on sheets similar to wall paper. To install it will amount to “cut, paste and clip on.” Currently a square meter is several hundred dollars, and I think in 25 years it could be $10 per m^2.

    LC

  22. solrey says:

    drflimmer, the approach taken by focus fusion with the dense plasma focus takes advantage of those instabilities rather than struggling to control them. A relatively weak toroidal magnetic field induces spin to control the direction of the axial electron and ion beams, and the B field also maintains ion temps hotter than the electron temps. It’s a very elegant and efficient approach, imho.

    Anyways, the National Ignition Facility is primarily for weapons research and really has little to do with generating electricity as a powerplant, even though they give it some “lip-service” as a stated goal.

    Lawrence Livermore Breaks Ground for NIF

    Peña’s praise of the Laboratory’s scientific achievements was echoed by Tauscher, Tarter, Assistant to the Secretary of Defense Harold Smith, University of California President Richard Atkinson, and Livermore Mayor Cathie Brown.
    Smith said that NIF underscores the importance of the collaborations between the national laboratories and the Department of Defense. “NIF marks a creative step toward meeting the needs of national security,” he said.

    National Ignition Campaign Execution Plan
    As stated in the NIF Justification of Mission Need, “The mission of the National ICF Program is threefold: (1) to play an essential role in accessing physics regimes of interest in nuclear weapon design and to provide nuclear weapon-related physics data, particularly in the area of secondary design; (2) to provide an aboveground simulation capability for nuclear weapon effects on strategic, tactical, and space assets (including sensors and command and
    control); and (3) to develop inertial fusion energy for civilian power production. These ICF applications require the achievement of ignition and propagating thermonuclear fusion burn. To achieve this goal, DOE is proposing the NIF.”

    There are no weapons capabilities in focus fusion, therefore no “gubment cheese” is getting tossed their way, which is a good thing because they have the freedom to do what they want.

  23. Thameron says:

    “Whatever gave you the idea that PV solar power is clean? Who told you that? It isn’t.”

    I didn’t say PV solar. I said solar unless you are going to make the case that solar thermal is also unclean in which case our world is pretty polluted since it is heated that way. Are mirrors toxic as well?

    “So please, stop spreading that biased garbage about how solar is going to save us all. It won’t.”

    Where exactly did I say solar was going to ‘save us all’? Was that in the same place where I said PV solar? i.e. nowhere? Does one small blog comment really count as ‘spreading that biased garbage’? Really?

    The only fusion power source currently making electricity here on the Earth is the sun. Saying fusion will be part of the electricity mix is optimistic at best. The first use of uncontrolled fusion energy by our species was in 1952. Engineers have had nearly six decades to master the technology of sustained controlled fusion and have yet to do so. In that distant future when a fusion power plant comes on line there may well be non-toxic solar panels that reduce or eliminate the need for it. And since it is the distant future we are speaking of we are free to speculate as we will.

  24. Lawrence B. Crowell says:

    @Thameron My only caveat with thermal solar energy is the word “thermal.” We have a hard time working with energy without converting it to heat and then converting that into mechanical or electro-mechanical forms. The entropy losses are considerable. However, it has been my thinking that small solar thermal systems could be devised; where solar concentrators focus photons on one piston of a Sterling engine and a cold water cycle cools the other piston which is pi/2 out of phase with the hot piston. So a modest system could provide a few kilowatts of electrical energy locally. These systems could be duplicated by the thousands, maybe millions, and provide local power sources relatively cheaply, particularly where there is no grid or distributed power.

    The problem with current fusion research is that it requires large energy input to get an energy output. There are some complicated scaling rules with this, but with current approaches it will require an enormous fusion plant to achieve breakthrough with substantially more energy out than what is input. I tend to have some jaded opinions of such mega-projects. I might be wrong about this lithium cycle idea, but this should be possible on much smaller scales. We are going to need constant stable energy sources on a distributed grid to make up for down times which will naturally occur with renewable energy sources.

    LC

  25. SpaceNinja says:

    I guarantee you that fusion, and even fission, power is cleaner than all fossil fuel based energies.

    And while it might not be cleaner than solar power, hydroelectric power, or others, it is many times more efficient and consistent.

    Nuclear power is ultimately the direction the world needs to go. Barrels of nuclear material can be stored safely. Millions upon millions of liters of toxic gases from fossil fuels can only (as of now) get spewed into the atmosphere, destroying ozone, giving our kids asthma, and influencing our climate.

  26. Lawrence B. Crowell says:

    I agree in part, but nuclear energy, particularly fission powered, is problematic on a number of fronts. Nuclear waste is an issue which continues to defy any answer that is completely satisfactory. Nuclear energy also does not come cheap either. I pretty strongly think we need to maximize the use of renewable forms as much as possible. Nuclear energy can then fill in the power-down episodes which will occur for various renewable sources.

    LC

  27. gopher65 says:

    Thameron: Ah, sorry. In my experience when people say “solar” they are rarely referring to thermal solar. Yeah, thermal solar, while a defuse power source, is great in certain situations. (IE, areas with low cloud cover.)

    Lawrence B. Crowell: Not all proposed fusion plants have gigantic. The Polywell project was originally conceived of as a way to produce micro-fusion reactors for use in space. Funding is now been largely provided by the US Navy, who are funding the research in an effort to find a replacement for their shipboard fission reactors.

    We should know in about a year whether or not a Polywell type micro-reactor is possible in the real world. If the project goes black, it works:P.

    Here’s a quick (very incomplete:P) rundown of Polywell:
    en.wikipedia.org/wiki/Polywell

  28. gopher65 says:

    … and obviously I meant diffuse, not defuse.

  29. Johnson says:

    I think these two methods are inefficient regarding energy usage. In my opinion, fusion methods that use electrostatic acceleration, as aneutronic reactor, has a more real chance of achieving a net gain
    without leaving radioactive waste.

  30. Lawrence B. Crowell says:

    This is a variant of my proposal for lithium fusion.

    LC

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