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The Seductive Promise of Fusion Energy

Few technologies hold more promise than fusion energy, but this energy source has remained maddeningly just beyond our reach for decades. As the NYT reports, the process behind harnessing fusion energy sounds easy enough:

The basic concept behind fusion is simple: Squeeze hydrogen atoms hard enough and they fuse together in helium. A helium atom weighs slightly less than the original hydrogen atoms, and by Einstein’s equation E = mc2, that liberated bit of mass turns into energy. Hydrogen is so abundant that unlike fossil fuels or fissionable material like uranium, it will never run out.

Yet accomplishing this in a controlled environment has proved devilishly difficult. Fusion can be thought of as the Brazil of energy: always the one to watch, whose day in the sun is perpetually 30 years away. It always helps to take a skeptical view of the kind of pro-fusion enthusiasm that has consistently outstripped the reality of the energy source’s progress over the years. With that said, recent progress at California’s Lawrence Livermore National Laboratory has injected new hope for the fusion dream. There researchers produced a fusion reaction that had an energy output greater than its input for the first time ever last fall. More:

[A] team headed by Omar A. Hurricane announced that it had used Livermore’s giant lasers to fuse hydrogen atoms and produce flashes of energy, like miniature hydrogen bombs. The amount of energy produced was tiny — the equivalent of what a 60-watt light bulb consumes in five minutes. But that was five times the output of attempts a couple of years ago.

The NYT concedes that “practical fusion would still likely be decades away,” a familiar refrain for any long-time fusion observers. But hope springs eternal, if only because of the tremendous upside fusion holds for humanity’s bid to produce enough energy to thrive in the centuries to come.

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  • TheRadicalModerate

    Because of the low efficiency of converting electrical energy to optical laser energy, a fuel pellet at NIF needs to generate something like 80 to 100 times the energy of the lasers impinging on it to be economically viable. Magnetic confinement, a la ITER, only needs to generate something like 5 to 8 times the input energy, but tokamaks don’t scale down: if you need a 10 or 20 gigawatt power plant, tokamaks might have a future. But even once the technology is developed, the investment to build a plant that size is huge, and the risks are non-trivial.

    My favorite right now is the Sandia MagLIF project (Magnetized Liner Inertial Fusion), which is pulsed like NIF, but uses a combination of a moderate magnetic field, two moderate laser beams, and the high-current Z Machine to crush a metallic liner around a fuel cylinder. They’ve had excellent simulation results and, even better, their early experiments seem to be verifying the simulations. I’d give this a much better chance of economic viability than either NIF or ITER/DEMO, but it’s still early days.

    Beyond the government labs and international projects, there are probably ten or fifteen small-scale projects looking at alternatives methods for fusion, ranging from things with a decent chance of success all the way down to pretty whacky, but these projects have the property that they could be revolutionary at small scale, which means that if any of the technologies hits paydirt, the cost of incremental deployment is very low, which gives the technology a decent chance at economic viability. I’d say that it’s just about as likely that viable fusion will emerge from somebody’s garage or some grimy little industrial park as it is that it comes from some half-trillion dollar research project.

    One last dirty little secret, though: Most of the fusion projects kicking around these days require tritium, which can’t be made at high scale and is therefore insanely expensive. Most projects plan on breeding tritium from neutrons hitting lithium in their heat-exchange blankets, but this process is unlikely to make enough tritium to make a plant self-sustaining. Tritium production is a huge impediment to the economic viability of fusion. There are a couple of projects that use different fuels, like deuterium-deuterium or hydrogen-boron, but these require even higher energy and are less efficient than deuterium-tritium. Still, a less-efficient reaction using easily refined fuels could be a winner.

    • ShadrachSmith

      If we have the fusion process, we will be able to get the tritium.
      There is lots of it near-by 🙂

      • TheRadicalModerate

        No, you’re thinking of helium-3, which can be used in yet another advanced fuel cycle. The only way to produce tritium is to make it, either in the blanket surrounding a fusion reaction or in a fission reactor. Tritium only has a half-life of 12 years, so it doesn’t occur naturally.

        • ShadrachSmith


  • Nick

    As a member of a National Research Council Board said to me once (its an old joke) “Fusion is the power of the future, and it always will be…”

    The break even here excluded many of the loses, and the press release talked about the energy just as it hit the pellet… Let Science Mag educate you……

    ….One requirement for ignition is that energy output should exceed the energy input from the laser, i.e., that gain (output divided by input) should be greater than 1. NIF’s laser input of 1.8 MJ is roughly the same as the kinetic energy of a 2-tonne truck traveling at 160 km/h (100 miles/h). The output of the reaction—14 kJ—is equivalent to the kinetic energy of a baseball traveling at half that speed. Numerically speaking, the gain is 0.0077. The experiment “is a good and necessary step, but there is a long way to go before you have energy for mankind,” Campbell says.

    The actual physics associated with NIF has not been what the scientist initially predicted. From the point of view of science, they are learning new things every day, and maybe the result of NIF will lead to fusion. But I think it is unlikely that NIF ever will.

    Hire someone who understands science to write these articles. Next time you won’t be embarrassed. Or perhaps read more than the initial press release.

    • Mahon1

      There’s nothing embarrassing about this article. Everyone knows that these giant lasers put out a lot more energy than a 60 watt bulb, and the article was clear that this was just another baby step. Hold the snark.

      • Nick

        “There researchers produced a fusion reaction that had an energy output greater than its input for the first time ever last fall….”

        Sorry. That is an absolutely incorrect statement. Anyone who understands the history of fusion research would have laughed at seeing it. The uninformed would be more uninformed. LLNL put out misleading press releases and a lot of people bought into them – because LLNL needs to keep congressional support, and congress critters generally are dumb as boots. 5 seconds of research shows it to be untrue (or actually asking a few questions.)

        Snark stands. Learn to read buddy.

        • Dan


  • rheddles

    Constant time to completion.

  • pst314

    Fusion = guaranteed employment for physicists. I.e., “we keep telling lies, and the government keeps giving us money to play with our favorite toys.”

  • Curious Mayhem

    It’s unlikely that current fusion research programs will ever lead to practical power. They’re plasma research programs, not applied science leading to cheaper power.

    There are alternatives to hydrogen-to-helium, like boron-to-carbon. The US Navy was funding this a while ago. I don’t know the status of it. Of course, there are also good alternatives to uranium-plutonium fission reactors, like thorium. But the political hurdles are great in the developed world. India is trying it, and the Japanese are heading back to fission power. But the Japanese are traveling to India to find out about better and safer approaches.

    • TheRadicalModerate

      It’s not boron to carbon, it’s hydrogren-1 + boron-11 –> 3 helium-4. The main advantage of this is that it’s aneutronic–the only reaction products are charged particles, so you don’t get neutrons making the reactor slightly radioactive.

      But the problem with this reaction is two-fold. First, it doesn’t generate as much energy as deuterium + tritium, so in addition to requiring more energy to make the reaction occur, getting to break-even is much harder. Second, and even worse, there’s a phenomenon called bremmstrahlung where energy leaks out of the system from electrons being flung around by the ions in the plasma. This gets worse as the square of the difference between the charge on the electron vs. the charge on the ions, and since boron has 5 times the charge of a a hydrogen nucleus, bremmstrahlung can be 25 times worse.

      You can get around this if you could have non-neutral beams of ions colliding with each other, but it’s very difficult to create that condition. There are a couple of projects trying to do just that, including the Navy project, which is looking at a technology called polywell. Things have gone very quiet from the polywell folks, and the guy heading up the project left to pursue other lines of research. That can’t be a good sign.

      I’m still optimistic about fusion, because we’re nowhere close to exhausting the bag of weird physics tricks you can apply to the problem. Both NIF and ITER are to a certain extent brute-forcing the problem. But it only takes one minor finesse of the state of the art to change the game completely.

      Also, note that increases in computing power are your friend here. It costs tens if not hundreds of millions of dollars to build a new fusion experiment, but nowhere near that to create a new simulation of a fusion experiment. So far, the computational tricks needed to do those simulations don’t yield accurate enough results to model the real physics. But there’s a level of computational power where that will suddenly change. When it does, you can try out new ideas very rapidly and very cheaply. I’m confident that that will lead to building viable fusion systems. Of course, that might be 30 years away, so I’m still within the parameters of the old joke that viable fusion is 30 years away and always will be.

      • Curious Mayhem

        I stand corrected. I must have been thinking of another reaction, although three He-4 have the same nucleons are C-12. So the reaction is p + B-11 -> He-4 + He-4 + He-4. I did know about the problem with bremsstrahlung (“breaking radiation,” for you non-German-speakers out there), but not the fact that the energy released is smaller than it is for D + T -> He-4 + n (the standard deuterium-tritium fusion reaction).

        Here’s a page on aneutronic reactions (fusion reactions that produce no neutrons in the products), with the energy released from each reaction:

        The reactions with He-3, Li-6, and p might work. But the “alternative fusion” research concentrates on p+B-11.

        (I think I was thinking of p + N-15 -> C-12 + He-4. There’s also Be-8 + He-4 -> C-12.)

  • BobSykes

    As far back as the late 1970’s, fusion was known to be a pipe-dream. The reality is that even if a fusion reactor could be built (and we are no closer than we were 40 years ago), it would be so large and expensive that the electrical power it produced would cost an order of magnitude more than an equivalent fission reactor. So even if successful, fusion reactors would have no possible civilian or military use.

    Then there is the radioactive waste problem. While a fusion reactor would produce spent fuel rods, neutron bombardment of its structure would transmute some trace elements into radioactive ones, which would require disposal as a low level radioactive waste.

    The lead physicists know all this, but projects like ITER and the laser ignition facility sustain upper class jet-set life styles, which are very nice. For the grunts doing the work, these projects have wasted the entire professional lives of literally thousands of gifted physicists. This must have crippled progress in many areas of physics.

    • Peripatetic

      What could possibly go wrong with someone named “Dr. Hurricane” in charge?

    • Curious Mayhem

      You meant, “While a fusion reactor would NOT produce spent fuel rods ….”

      • BobSykes

        Yes. Sorry, too much caffeine. Or maybe not enough. Let’s go with the latter.

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