Controlled Nuclear Fusion: Forget about it

Man or woman doing a technical thing with a thingy told with laser induced nuclear fusion.

Man or woman adjusting the ‘target positioner’ (I think) within the target chamber of the US Lawrence Livermore National Laboratory.

The future is very difficult to predict. But I am prepared to put on record my belief that controlled nuclear fusion as a source of power on Earth will never be achieved.

This is not something I want to believe. And the intermittent drip of news stories about ‘progress‘ and ‘breakthroughs‘ might make one think that the technique would eventually yield to humanity’s collective ingenuity.

But  in fact that just isn’t going to happen. Let me explain just some of the problems and you can judge for yourself whether you think it will ever work.

One option for controlled fusion is called Inertial Fusion Energy, and the centre of research is the US National Ignition Facility. Here the most powerful laser on Earth can be focussed onto a pellet of deuterium and tritium and the temperature and pressure reached induce fusion. The process releases neutrons and a flash of X-rays and UV light which are captured to produce heat which generates electricity using a conventional steam generator.

  • Reality Check#1: Currently one pellet can be hit every few hours. In order to make a one gigawatt power plant this process must be speeded up so that around 10 pellets every second are ignited. This is equivalent to firing a ‘machine gun’ into the centre of the high vacuum reaction chamber, but none of the ‘bullets’ must reach the other side of the chamber: every one must be tracked individually in-flight and blasted by the most powerful laser on Earth. No misses can be tolerated, otherwise a ‘bullet’ will hit the far side of the chamber. This process must continue night and day for months on end. The explosions will release energy at a rate of several gigawatts of thermal power, but this must not affect the vacuum through which the lasers reach their target. Every ‘bullet’ must be identical to within a manufacturing tolerance of 1 micrometre. Getting all this to work is IMHO impossible.

The other option for controlled fusion is called magnetic plasma confinement, and the centre of research is ITER being built near Marseille in the south of France. Here a plasma of deuterium and tritium is heated to around 150 million °C (about 10 times hotter than the centre of the Sun).

  • Reality Check#2: About one metre away from the 150 million degree plasma releasing neutrons with several gigawatts of energy are gigantic superconducting magnets at approximately 4 degrees above absolute zero. Superconducting materials are sensitive to radiation and their special property will be lost if they are intensely irradiated. To visualise the  temperature, think of about 1 million one kilowatt heaters trapped in a room the size of a small theatre. The plasma must not touch the walls of its container ever. Once initiated, the facility will become intensely radioactive and humans can never enter it again, and the hot plasma must remain confined for months on end exceeding the few seconds that have been achieved to date. Getting all this to work is IMHO impossible.

And even if we suppose these impossible things were somehow made possible by the application of ingenuity, good fortune and cash, there is one more ‘show stopper’: the availability of tritium.  In either approach, deuterium (which is found in seawater) is fused with tritium (which is not found naturally at all). Where will all the tritium come from?

  • Reality Check#3: The tritium must be generated by capturing every neutron released in the fusion reaction in a blanket of lithium metal (or a salt containing lithium). The neutrons from the miniature star in the reactor induce a reaction in the nucleus of one of the isotopes of lithium (7) which causes it to split in two, releasing helium and tritium. The tritium must be captured and fed back into the fusion reaction. This process must operate close to 100% efficiency otherwise the plant will run out of tritium. Getting all this to work is IMHO impossible.

I am a technological utopian: I think technology can make life better for people. And I would really like to believe that fusion will ‘somehow work’. But when I look at these obstacles, I just can’t see how anyone can overcome them.

As Sherlock Holmes might have said:

When you have eliminated all which is impossible, then whatever remains, however disappointing, must be the truth. 

16 Responses to “Controlled Nuclear Fusion: Forget about it”

  1. Sean Ellis Says:

    I agree on the inertial fusion system – just too complex for sustained use. Tokamak might be able to work but it will need to be big. I was wondering if you had a view on dense plasma focus devices as a possible “third way”? It seems plausible to an amateur science fan like me, but as usual the devil will be in the details. And the scaling.

    • protonsforbreakfast Says:

      Sean

      I am not aware of the dense plasma focus method. As I understand it, in the Tokamak configuration there are – still – problems controlling the plasma and it cannot be held indefinitely. At high power in JET only a few seconds were possible. Does a ‘dense plasma’ pulse periodically and so not need containment?

      M

      • Sean Ellis Says:

        Yes, dense plasma focus (google for “focus fusion”) uses the plasma instabilities that plague tokamaks to pinch the plasma into a small, hot space. It’s definitely hot enough for fusion and has been demonstrated at small scale. Some people involved say that it should scale linearly and also possibly work with aneutronic fuels like Boron+Hydrogen. I know enough physics to realise this is plausible, and I love it to work, but there are a few small alarm bells ringing in the back of my mind and I have yet to see a convincing examination of the evidence by a neutral third party.

      • protonsforbreakfast Says:

        Sean

        Thank you for the clarification. It sounds like a pulse process rather than continuous process so there is in’t such a stringent requirement for stability. But I would have thought the other side of the coin is that it would be hard to do reproducibly.

        Hey Ho.

        Time will tell. But I will look out for mention o this option.

        M

        On 15/10/2013 10:59 pm, “Protons for Breakfast Blog”

  2. Leonid Says:

    what about aneutronic fusion?

    • protonsforbreakfast Says:

      That is a beautiful video but I am afraid I just can’t understand it. Sorry. And I don’t know what ‘aneutronic fusion’ is either. Sorry again.

  3. Robert Steinhaus Says:

    I think the ultimate importance of fusion to the world is such as to justify continued effort toward the goal. D-D fusion of seawater is capable of powering the planet at the level of of 60 Terawatts (about 4X the current world energy usage) for 8.33 billion years (longer than the earth has existed and longer than the sun will shine).

    Contrary to popular belief (Fusion is always 50 years away . . .) there is an impure fusion process that works producing net energy and large useful amounts of fusion power – enough power to transform the world economy and eliminate fossil fuel burning for production of electricity while effectively addressing climate challenges.

    The 1970s versions of Fission Ignited Fusion (FIF) were practical and demonstrated producing very high fractions of their total energy yield (>95%) from fusion. Small refinements in those early LANL and LLNL designs would probably have raised the fusion yield to >99%, but work on this practical impure fusion approach was dropped in favor of pure fusion approaches that were –

    * technically interesting

    * did not have any direct weapons lineage and as a result were less frightening to the public

    * had better political support and connections in Government

    (but which have produced no net energy in over 40 years and still struggle after decades to reach break even energy).

    ITER and NIF today struggle to reach Physics Q=1, which is a much smaller achievement than Engineering Qe=1 where the energy from fusion matches the energy required from the electrical power mains to run the experiment.

    Impure fusion experiments that use nuclear fission and tiny amounts of fissile material to produce the conditions for fusion and initiate the burning of D-T and D-D fusion plasmas have worked reliably since 1952 and produce not Engineering Qe=1 but Qe=100,000 accompanied by production of large commercially significant amounts of fusion energy.

    NIF researchers recently reported producing 15 x10^15 (15 quadrillion) neutrons in their best shot which occurred in late September 2013. NIF uses 422 MJ (million joules) of electric energy to charge its large capacitor banks and drive a football-stadium-sized laser that focused its light on a pellet of frozen deuterium and tritium fuel. (Deuterium and tritium are isotopes of hydrogen.) In a complex sequence of events, the light heats a heavy metal shell, producing X-rays, then the X-rays blow outer layers off of the DT pellet, and the force generated by the blow-off compresses the pellet while the laser heats it to fusion temperatures. The energy actually produced from all fusion reactions was about 14 kJ of energy. From the standpoint of engineering break even as measured by Qe=1, NIF currently produces

    0.014 MJ / 422 MJ x 100% = 0.00332% of the energy from fusion that it would have to produce to reach engineering break-even energy.

    Why wait to introduce practical forms of fusion power today?

    Why not use fusion physics proven to work on earth that has worked reliably since 1952 to start generating Gigawatts of clean fusion power per power plant with impure Fission Ignited Fusion and then introduce pure fusion power plants when they are technically ready. The world needs a new source of energy today to replace fossil fuels which dwindle toward unavailability – that energy could be practical Fission Ignited Fusion power plants that are small, cost effective, and safely mounted underground with minimal surface footprint.

    [1] – A Third Way Towards the Controlled Release of Nuclear Energy
    bv Fission and Fusion by F. Winterberg
    http://www.znaturforsch.com/aa/v59a/s59a0325.pdf

    • protonsforbreakfast Says:

      You make a good point. But the dual process comes – in my mind at least – under the category ‘Next Generation Fission’. There seems to be no taste world wide for anyone to seriously invest in >any< of the many much safer schemes for fission.

      As you say it seems irrational to go after this most difficult of goals and ignore much more achievable ones. I can only guess it is because the paymasters just don't grasp the engineering and physical realities.

      All the best

      Michael

  4. Dave Ansell Says:

    Whether they are possible or not the sheer amount of precision engineering is going to make both strategies expensive. I doubt the alternatives are easy either but I do think it is worth throwing a few tens of million at them to see what happens.

  5. The Monster from Polaris Says:

    Having actually worked on the ITER project and done calculations on these matters, I have to disagree with your Reality Checks #2 and 3.

    >Superconducting materials are sensitive to radiation and their special property will be lost if they are intensely irradiated.

    The neutron and gamma flux at the superconducting coils of ITER can be kept within acceptable limits.

    >The plasma must not touch the walls of its container ever.

    This does not agree with my understanding of the issue, though on this question you should ask a plasma physics specialist rather than me. The temperature of the plasma will certainly be very high, but thanks to its very low density the energy content will be modest.

    >Once initiated, the facility will become intensely radioactive

    Correct, except that the word ‘intensely’ is debatable.

    > and humans can never enter it again,

    Wrong. Humans can do hands-on maintenance at the ends of the ports in ITER within 1 million seconds (less than 2 weeks) after shutdown. Of course, entering the plasma chamber would be more problematic, but that won’t be necessary. The maintenance can be done remotely.

    >the hot plasma must remain confined for months on end

    Not necessarily, though the confinement time will need to be longer than a few seconds.

    >The tritium must be generated by capturing every neutron released in the fusion reaction in a blanket of lithium metal (or a salt containing lithium). The neutrons from the miniature star in the reactor induce a reaction in the nucleus of one of the isotopes of lithium (7) which causes it to split in two, releasing helium and tritium. The tritium must be captured and fed back into the fusion reaction. This process must operate close to 100% efficiency otherwise the plant will run out of tritium.

    Wrong. Including beryllium or lead as a neutron multiplier will give enough extra neutrons from (n,2n) reactions that you can afford to lose several percent of the neutrons and still breed enough tritium (mainly from lithium-6 rather than -7) for a reactor to cover its own tritium needs. This appears to be feasible. (Though there may still be some doubt about how efficiently the tritium can be recovered. I believe that’s one of the questions ITER will have to answer.)

    Of course, ITER won’t yet be an actual power-producing reactor. The design challenges involved in such a reactor are more formidable but can probably be met.

    I suggest you read the technical literature, such as the journal ‘Fusion Engineering and Design’. Even my own doctoral dissertation, F. Wasastjerna: ‘Using MCNP for fusion neutronics’, contains some useful material.

  6. Rober2D2 Says:

    Never is pehaps too long, but I would say we must forget about commercial fusion energy in a near foreseeable future. I have watched some documentaries about different fusion technologies being investigated. My conclusion is: Fusion is just too complex to be a commercial success. Even when technical barriers are surpassed (In let’s say 100 years), it will simply be too expensive comparing to the alternatives. I know, fusion fuel is very cheap, but like wind and solar, most of the cost is the construction and assembly (And there fuel is even cheaper). But there is another reason: After producing their own power from solar and wind, would fusion be interesting for customers.

    • protonsforbreakfast Says:

      I agree with your reservations. I fully believe that technical feasibility will be demosntrated – but in my opinion this will never (and I mean never) become an engineering reality that solves more problems than it creates.

  7. Steve Knight Says:

    Important factor is cost of making laser fusion targets, requires incredible engineering, current cost is about $2,500 each, you need to get this down to ~25 cents each and make half a million per day for a power station to make sense. They are not readily amenable to mass production.

  8. telescoper Says:

    Reblogged this on In the Dark and commented:
    You’ve probably heard that Lockheed Martin has generated a lot of excitement with a recent announcement about a “breakthrough” in nuclear fusion technology. Here’s a pessimistic post from last year. I wonder if it will be proved wrong?

  9. Joseph Nebus Says:

    I have to agree with the position that useful energy-producing fusion just isn’t going to happen anytime soon. I have the feeling that we just haven’t got the conceptual background for a working system just yet, and it’s something that’s going to require some surprising and not-presently-developed path. Unfortunately that doesn’t help much in saying what path to take.

  10. Is anything truly impossible? | Protons for Breakfast Blog Says:

    […] I explained my reasons for considering the project to be impossible here.  […]

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