Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

ITER useless

  1. Aug 16, 2010 #1
    As the cost of ITER is now estimated at 16G€, I want to point out that such a tokamak is completely useless, because it requires unavailable tritium.

    That is:
    - Tritium does not exist naturally, because its life is about 20 years and it isn't produced on Earth by any process;
    "in the ocean" is just false, by ignorance or by deception.
    - Tritium is produced by uranium reactors, in tiny amounts. A fission reaction produces 200MeV heat to create less than one available neutron, which is necessary to produce one tritium atom, for instance from lithium. Then, one tritium consumed in a tokamak produces less than 20MeV heat. In other words, one 1GW tokamak needs >10GW fission reactors operating.
    - Just as any magnetic confinement reactors, Tokamaks don't produce tritium. One reason: the D-T reaction produces only one neutron, and one neutron would produce less than one tritium, for instance from a lithium cover. Some would like to pretend that "neutron multiplicators" like lead achieve a tritium regeneration factor of 1.1 but this is a theoretical best case supposing there are no other design constraints on a tokamak... And well, there are design constraints, which in fact prevent doing anything more than keeping the plasma hot and confined...
    - Tokamaks can't consume anything else than tritium in any foreseeable future. Other reactions than D-T, like D-D or D-Li, require conditions even much more difficult to achieve in the plasma. Nobody would predict a number of half-centuries more before these reactions are usable.


    - Tokamaks can't replace fission reactors, not even a small fraction of them.
    - Tokamaks are useless. ITER is useless.
    - We can save 16G€ worth of physicist time to develop useful and sensible projects, like geothermal energy, or like storage of wind electricity or Solar heat. We would have solved all of them with the money already wasted in tokamaks.
  2. jcsd
  3. Aug 16, 2010 #2


    User Avatar
    Science Advisor
    Gold Member

    This is a joke, right? Are you seriously comparing an experimental research reactor to a commercial power plant?

    While it is true that commercial light water fission reactors produce a little bit of tritium, it is not harnessed in this way because it is far easier to breed tritium from either lithium or boron using a research reactor.

    Furthermore, it's not as if you would be throwing away all those gigawatts of heat from the commercial-sized power reactor just to make tritium. Using your example (which is totally incorrect for several other reasons), you would be making >10GW of energy from fission, and get 1 GW of fusion fuel as a bonus on top of that.

    Additionally, if you had a working practical tokamak, it would indeed produce its own tritium using the same method as above - the extra neutrons from fusion are absorbed in lithium to create more tritium.

    So essentially, you are advocating cancelling research in unlimited clean power in the near future to have a couple gigawatts of unreliable, extremely expensive and inefficient "renewable" power now. Good call.
  4. Aug 17, 2010 #3
    Perfectly serious, and I stand by.

    A research reactor would produce >10GW heat just as a power plant reactor would, when producing tritium for the 1GW tokamak. So the tokamak is useless, as it can't replace the fission reactors, not even a fraction of them.

    Tokamaks can't produce their own tritium. Already explained in the first post, third item in the list: "extra neutrons" are mathematically too few.


    You add "clean" fusion power as an additional usual promise by proponents. This is false as well.

    As fusion produces 1 neutron for 20MeV heat, instead of 3 neutrons for 200MeV heat for fission, the radioactivity induced in reactor materials would be 3 times higher than in fission reactors.

    Or in fact much worse, because with the quite higher doses of neutrons and their much higher energy, the activation of surrounding materials gets frankly impossible to control. In fission reactors, avoiding some elements (like traces of cobalt in steel) limits the effects of neutron irradiation. But with spallation induced by energetic fusion radiation, as well as successive neutron absorption, such measures get inefficient.


    So research into tokamaks is not only very expensive and long. At some point, we'll realize they are dirty and we have no tritium to feed them.

    Normal and sound management would require to solve the tritium impossibility before wasting any cent in this huge and meaningless enterprise, and abandon it if it can't be solved.


    QuantumPion's last sentence is the usual argument directed at a less informed public and shouldn't need an answer in a science forum, does it?
  5. Aug 17, 2010 #4


    User Avatar
    Science Advisor
    Gold Member

    No it wouldn't. A research reactor is not a commercial power reactor. You do not need a 10 GW thermal LWR to create a neutron source to breed tritium. You would never do this anyway, as a water-cooled power reactor is designed specifically to make efficient use of neutrons and not letting them be absorbed in water, where as a research reactor's purpose is to create lots of extra neutrons for whatever secondary purpose is required.

    Even if you did want to use a commercial power reactor to also breed tritium, you would not be throwing away all of the thermal energy the reactor produces to create that tritum. The thermal power would still be fully utilized to generate electricity, regardless of whether you are also making tritium or not. You would end up with all of the electricity generated by the fission reactor, in addition to the fusion fuel you created for use in a fusion reactor. While in a fusion reactor much of the nuclear energy is carried away by the neutrons, in fission reactors only a few percent is as power reactors are designed to not waste neutrons in the first place.

    Anyways, the ITER could not replace a commercial nuclear power plant any more than the large hadron collider could because it is a research reactor that is not designed or intended to be capable of producing net electric power.

    I'm not a fusion engineer so I don't know all of the engineering challenges related to tokamak tritium breeding. However I do know that it is at least physically possible and a quick google search on the matter lists lots of different white papers on the the issue. So if you would provide a link to your source proving that it is in fact impossible, that would be helpful.

    This is entirely inaccurate. You are ignoring the entire chain of fission products produced by that single fission event, the radioactivity is by no means limited to just the neutrons produced. One fission event can lead to dozens of radioactive atoms down the line with half lives in the tens of thousands of years.

    Commercial fission reactors generate hundreds of metric tons of spent fuel which is extremely radioactive and requires reprocessing or geological repository to get rid of. This radioactive waste is composed of a mix of extremely-long-lived actinides and fission products with half-lives in the ~1-10,000 year range.

    By comparison, neutron activation of structural material produces radioisotopes of light elements which have short half lives. A fission reactor produces some of these due to the components that make up the fuel rods, as well as the reactor vessel itself. A fusion reactor would produce more, however this is far less of a deal then the spent fission fuel itself is as the decommissioning of a fusion reactor would not require any type of deep-geological repository.

    I don't know where you get the idea that neutron activation is "impossible to control". It is in fact trivially easy to control, and is done so at every nuclear fission power plant in operation. Your last paragraph is entirely baseless and without merit or source.

    One of the goals of the ITER project is to test the capability of a tokamak to breed tritium. As the primary source of fusion fuel will be the fusion plants themselves, how do you propose we "solve the problem" of not having enough tritium before doing the research to solve the problem of not having enough tritium? You are suggesting that we should cancel research in the project because the project has not been completed successfully yet. It is ridiculous circular logical fallacy.
  6. Aug 17, 2010 #5
    Simple google search disagrees with your analysis:

    "With three-dimensional modeling and neutron transport analysis, a tokamak with a low technology blanket containing beryllium was found to have a tritium breeding ratio of 1.54 tritons per DT neutron. Such a device would have a net tritium production capability of 9.1 kg/yr from 450 MW of fusion power at 70% capacity factor."
    From the abstract of: Tritium breeding analysis of a tokamak magnetic fusion production reactor
    Found at:

    Heavy water reactors, such as CANDU, produce more tritium than light water reactors per GW heat produced. They are also much more neutron efficient and could be designed to produce more tritium.

    Tritium can also be made from lithium in both fast and thermal reactors. Research reactors designed for irradiation can also be designed with higher flux to power ratio for example SLOWPOKEs.
  7. Aug 17, 2010 #6
    Do you expect something magic in the number of neutrons available from fission, just by choosing the type of reactor?

    By its very nature, one 235U gives 200MeV and about 2.5 neutrons (slightly more with fast neutrons), of which one is consumed by the next reaction of the sustained chain, leaving a maximum of 1.5 neutron available for the production of radioisotopes, in this case tritium.

    Research reactors try to make most of these 1.5 neutrons available while power plants don't. But this 1.5 is the maximum. Add many big losses meanwhile, and you get in fact much more than 10GW heat from fission when consuming the tritium to make 1GW fusion power.


    Of course, these 10GW would be used to produce electricity! But then, these uranium reactors being still necessary would just produce 11GW, instead of squandering 16G€ to make the last 1GW!
  8. Aug 17, 2010 #7
    I wrote precisely "radioactivity induced in reactor materials" and am happy to see you agree with me. You introduced the actinides and the fission products in the discussion, I didn't.

    And I wrote it because, as usual, someone claimed fusion would be clean, which it isn't.


    This induced radioactivity is quite different from (and worse than) the one known in fission reactors, both from dose and energy. Please read again my input.
  9. Aug 17, 2010 #8
    "The capability of Tokamak to breed tritium... has not been completed successfully yet"
    -> More accurately, this insurmountable flaw had been concealed up to recently!
    In fact, this demo was added on ITER only because some specialists had raised the objection.

    ITER is to have a small piece of demonstrating thing intended to show some tritium production but doesn't even intend to breed more tritium than it consumes. Which will prove nothing, because production is already known by other means - it's all a matter of quantity, or breeding more than it consumes.

    Claimed breeding ratios suppose the whole cavity to be covered with some special and pure material to get a breeding factor slightly over 1. But then, tokamaks put some other design constraints on their walls, you know? Like resistance to temperature and neutron flux, vacuum cleanliness even when hot, magnetic and electric properties... These constraints alone are hardly met now, with designers hoping graphite-graphite as the material that may perhaps fit.

    And as this objection looks insurmountable, it shall be treated first, before squandering huge amounts.
  10. Aug 17, 2010 #9


    User Avatar

    Staff: Mentor

    This is essentially incorrect, even to the point of misinformation!

    Various folks are looking to extract deuterium from seawater, not tritium. Deuterium is considered an abundant fuel for the future. Wonder from where deuterium is extracted for CANDU reactors?

    Of the 200 MeV from fission, about ~5 or so MeV is coming from the fast neutrons (~ 2 MeV/neutron on average), while the rest comes from fission products (~165 MeV), betas, and gamma radiation.

    Fission reactors use 'burnable absorbers', e.g., gadolinia, erbia, or boron to absorb neutrons in order to control excess reactivity and power distribution in the core. If one were to introduce Li-6 as a burnable absorber, then one simply reduces a neutronically equivalent amount of the other absorbers. So using Li-6 to make tritium is not a disadvantage per se, but it does produce a limited amount of tritium.

    There are various schemes for using fusion neutrons. The 14.1 MeV neutron can be slowed in a blanket and most of that thermal energy would be recovered before the neutron is absorbed - preferentially by Li-6 to make more T, or by U-238 or Th-232 to make fissile material. However, using fusion reactors to breed Pu-239 or U-233 is considered politically incorrect from a proliferation standpoint.

    There is also the potential for (n, 2n) reactions in the blanket.

    And who is the "Some [who] would like to pretend that "neutron multiplicators" like lead . . ."?

    Not true.
    d + d => t + p (~50%), He3 + n (~50%). Otherwise neutrons are used to produce tritium via Li6(n,α)T, which is also a reaction that can be applied in a fission reactor.

    Again, 3 neutrons to do not produce 200 MeV. A single neutron causes a fission while the remaining neutrons are absorbed in the fuel or structural matierals.

    There are significant challenges to materials in fusion reactors, and certain d+d or d+He3, or d+Li require more challenging confinement conditions, or perhaps more challenging feed and bleed processes.

    ITER is not necessarily optimally configured for a commerical system.
  11. Aug 17, 2010 #10


    User Avatar
    Science Advisor

    BALONEY!!! More misinformation / disinformation due to poor scholarship on the
    part of this poster.

    There IS a natural process that creates Tritium. One of the constituents of the radiation
    from the Sun that we call the "solar wind" is fast neutrons. Those fast neutrons interact
    with the ordinary Nitrogen in our atmosphere giving the following reaction.

    7N14 + 0n1 --> 6C12 + 1T3



    This natural process creates Tritium high in the atmosphere. The Tritium combines
    with Oxygen and rains to the ground as slightly tritiated water. All water on the planet
    is slightly radioactive due to the presence of natural Tritium.

    Dr. Gregory Greenman
    Last edited: Aug 17, 2010
  12. Aug 23, 2010 #11
    I don't have a dog in this fight, but I am disconcerted. Please elaborate in the following context.
    1: The half-life of a free neutron is about 10 minutes, giving a mean lifetime of some 14 minutes.
    2: A solar photon takes about 8 minutes to reach us; how many half-lives would it take a 4MeV neutron to reach us? (I do realise that it takes a lot of half-lives to get rid of all the neutrons!)
    3: Given your response to those questions, are solar neutrons (especially fast neutrons) still a major source of isotopes in our atmosphere?

    Thanks if you can help.
  13. Aug 23, 2010 #12
    Cosmic ray spallation produces Tritium in our atmosphere.
  14. Aug 24, 2010 #13
    Thanks GP; that I have no difficulty with.
  15. Aug 30, 2010 #14
    A D-T fusion tokamak power reactor will produce its own tritium in-situ through transmutation of the lithium tritium-breeding blanket, as I'm sure most of you know.

    Nobody denies that Teller-Ulam bombs fuelled with LiD (and very little, if any, 3H initially inside the weapon) work very effectively, do they?
  16. Sep 1, 2010 #15
    What is the point of fusion?

    Is it simply that fusion is more politically acceptable than fission? Lets say we could be realistic about nuclear. Is the radioactive waste (e.g., activated shielding) from a tokamak honestly so much better to deal with than that from a fission station? (I thought both were trivial to deal with, especially compared with radioactive coal ash.) Is there a genuine shortage of fission fuel that fusion will overcome? Do we expect fusion to work out economically superior to fission and to, say, solar thermal? Is it safer than fission (can I presume that both are safer than solar, and far safer than coal)?
  17. Sep 1, 2010 #16


    User Avatar
    Science Advisor
    Gold Member

    Reprocessing spent fission fuel is definitely not trivial, it requires very expensive facilities and safeguards. Fusion has none of those drawbacks. Furthermore, while fission power is very safe, as history has shown it is not foolproof. Fusion has no risk of a catastrophe such as Chernobyl/TMI/SL-1/Windscale occurring. Also there is no proliferation concern with fusion fuel.

    Once the engineering technology to make fusion practical is developed, I believe it will be the most effective source of power for humanity. Renewable sources such as solar or wind can never be economical, the power density is just too low.

    As a little aside: while fission fuel is quite plentiful, it is not as unlimited and ubiquitous as fusion fuel. And once fission fuel is used up, it is gone forever and there is no way to replenish it, since it can only be created in supernovas. My conjecture is that humanity may be better served by saving as much fission fuel as we can for the distant future for space travel applications, where its high power density may be irreplaceable by other sources.
  18. Sep 2, 2010 #17
    Frankly QP, although I am a slightly sceptical supporter of fusion power, I certainly am a supporter. I do not think that the things you said should need saying. As humans we should be investigating whatever we reasonably can investigate and in particular whatever might reasonably be expected to improve our position relative to nature. Such investigations would include both the academic and the possibly applicable.
    Fusion research meets both criteria. How many lines of fusion research we should be investigating apart from Tokamak is a moot point. I would prefer to see several more, given that there are quite a few ideas that look promising.
    But that is a matter of detail.
    Go well,
  19. Oct 3, 2010 #18
    Several years ago it seems public information/talks about plasma fusion power (Tokamaks, Stellarators, or?) at Columbia University just stopped. The rumor was there was some kind of realization or breakthrough that meant the reaction was easy to achieve and could even be used for a bomb. The only person I knew there said it was now classified and he wouldn't talk about it. Does anybody have any idea what this is about or is it just baloney? (I thought something like this might be possible with opposing neutral beam heaters, but thats probably not it.)
  20. Oct 3, 2010 #19


    User Avatar

    Staff: Mentor

    Fusion power is based on a controlled fusion process with a moderate power density.

    Thermonuclear (fusion) weapons are based on a short term (microsecond) process that it is initiated with a fission trigger.

    The two processes are very different, as is a nuclear power plant and conventional fission warhead.

    So far controlled thermonuclear (fusion) for the commercial production of electrical energy has proven elusive.
  21. Nov 12, 2010 #20
    9 scientists in a room... 10 different opinions.

    I agree every aspect of fusion should be fully funded and researched.

    If only we could generate muons more efficiently!!! (And make them a more efficient catalyst).

    It's always been my imagination that real working fusion power is going to have to use all the advantages of each way to generate fusion... and somehow eliminate all the drawbacks of each of these methods.

    My greatest fear is that ITER will fizzle out (pun intended) and research dollars for fusion will dry up faster that a puddle of heavy water.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook