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Why can't we use nuclear waste in nuclear reactors?

  1. Feb 11, 2015 #1
    If nuclear waste is more radioactive than the nuclear fuel it is derived from, why can't it be used in a reactor?
     
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  3. Feb 11, 2015 #2

    mfb

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    Nuclear reactors mainly use (induced) nuclear fission. Radioactive decays of fission products contribute to the power, but not enough to make a power plant based on them worth the effort.
     
  4. Feb 12, 2015 #3

    QuantumPion

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    If by nuclear waste you mean spent nuclear fuel, you can, but the fuel must be reprocessed first to remove fission products which hinder the nuclear chain reaction. This is expensive, and historically it has been cheaper and easier to just make new fuel than reprocess spent fuel.

    If by nuclear waste you mean just radioactive material in general, there are some radioactive materials which can be used to generate power in radioisotope thermal generators. However these RTG's use specialized materials made specifically for them, not just random radioactive waste. The energy output of low level radioactive waste is simply insignificant compared to conventional macroscopic energy sources.
     
  5. Feb 12, 2015 #4
    I tend to think that spent nuclear fuel is a vastly underutilized resource. Right now it spend years sitting in spent fuel ponds where energy is used to keep it cool. Instead of that it seems like it would make more sense to use the heat it produces to generate more electricity. Sort of a reactor within a reactor that could be used to provide back up power to cool the main reactor if needed or to supply more electricity to the grid during normal operations.
     
    Last edited: Feb 12, 2015
  6. Feb 13, 2015 #5

    anorlunda

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    The flippant answer to the OP question is Jimmy Carter.

    Before Carter became president, the economics of nuclear power assumed thst spent fuel would be reprocessed. When he came into office he forbade it. That, plus the incident at Three Mile Island doomed the industry.

    To be fair, Carter had some good reasons. The first reprocessing plant at West Valley NY was a horrible fiasco. It gave a black eye to the whole idea of reprocessing.
     
  7. Feb 13, 2015 #6

    QuantumPion

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    Spent fuel does not generate enough heat to be economically useful. There are already other more robust sources of backup power.
     
  8. Feb 13, 2015 #7

    mfb

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    The idea is so obvious that it has been studied in detail - and as you can see from the non-existence of its usage, it is not economically viable.

    @anorlunda: Carter might have been relevant for the US, but nuclear power is used in many countries.
     
  9. Feb 13, 2015 #8

    Nugatory

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    As I read the question, OP isn't asking about extracting fissile material from the waste for use as fuel (which is what is usually meant by "reprocessing") but rather about using the energy released by the ongoing decay of the fission products themselves.
     
  10. Feb 13, 2015 #9
    Perhaps your right about it not being economical for back up, but some people still seem interested in using it for some things.
    http://en.wikipedia.org/wiki/Spent_fuel_pool#Other_possible_configurations
     
  11. Feb 13, 2015 #10
    interesting...as someone as already said they are already used in some fields....some satellites use them to produce directly electrical energy.
     
  12. Feb 13, 2015 #11
    It can be used but it is tricky and less profitable if the costs for waste disposal are not considered. There are pilot projects e.g. MYRRHA in Belgium (http://www.siler.eu/public/DeBruyn.pdf).
     
  13. Feb 13, 2015 #12

    DrDu

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    I don't remember where and when, but some physicist wrote a request to use a barrel of highly radioactive fuel to generate hot water for its own house. For some strange reason, his request was declined :-)
     
  14. Feb 13, 2015 #13

    Quantum Defect

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    The Wikipedia page has some interesting history on nuclear reprocessing. Worries of nuclear proliferation were responsible for Ford/Carter's actions in the US. Reagan lifted the ban, and there was some recent construction at Savannah River for a mixed oxide fuel fabrication facility, but nothing has been completed. Other countries have continued fuel reprocessing, as outlined in the table in the wiki article: http://en.wikipedia.org/wiki/Nuclear_reprocessing

    See also: http://www.fas.org/sgp/crs/nuke/RS22542.pdf for a very nice timeline...
     
  15. Feb 13, 2015 #14

    russ_watters

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    A more direct answer to the OP's question, perhaps:
    http://en.wikipedia.org/wiki/Radioactive_waste#Nuclear_fuel_cycle
     
  16. Feb 13, 2015 #15

    russ_watters

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    My understanding is that reprocessing is done in many countries, though, yes, it is more expensive than once-through...though there can be political considerations that trump economics on either side of the issue.
    http://en.wikipedia.org/wiki/Nuclear_reprocessing#List_of_sites

    Perhaps more to the point, for the US, right now the economic analysis of the issue is incomplete or even moot: The US has tried and failed (thus far) to get a permanent waste storage facility commissioned and as a result, the true cost of the principal alternative to reprocessing can't readily be calculated. Sure, storage could and probably should be relatively easy and cheap, but then again, so should nuclear power itself!
     
    Last edited: Feb 13, 2015
  17. Feb 13, 2015 #16
  18. Feb 13, 2015 #17
    Fast neutron reactors can burn most of the nuclear wastes as fuel. The USA used to have some fast neutron reactors, but as far as I know, they have all been shut down for political reasons and safety concerns. Criticality accidents are more dangerous in fast neutron reactors than light water reactors since there are fewer negative feedback mechanisms in place if the coolant evaporates. These issues can probably be solved but there hasn't been a political will, since there is a proliferation risk. I think worrying about proliferation is stupid, since plentiful clean energy will do a lot more for peace than any political blustering.
     
  19. Feb 13, 2015 #18

    mfb

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    I think this thread was never about reprocessing.
    @Felchi asked why the radioactivity of nuclear waste is not used in a reactor.
     
  20. Feb 14, 2015 #19

    Astronuc

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    Spent fuel is considered high level waste, more or less, under the current strategy of once-through fuel cycle.

    In the early decades (60s and 70s) of the commercial nuclear industry, there was some thought about recycling Pu and unused U in commercial fuel. This would require reprocessing plants to separate the 3 to 4% of fuel that became fission products as a result of the process. Back then, fuel cycles were designed on the basis of three or four annual cycles. Now most plants in the US operate on 18 of 24 month cycles, and discharge burnups are in the range of 4 to 5% of initial metal atoms. That is not very conducive for recycling, since with the higher burnups and residence times, the production of transuranics Pu, Am, Cm increases, and that requires more remote handling and shielding for reprocessing. In addition, one still has to separate all the fission products, which have to be immobilized in some vitrified (glass) form that is chemically stable (very little or no leaching) in storage for thousands of years.

    The spent fuel generates very low levels of thermal energy, on the order of fractions of 1% of the power that the fission process produces. One could not develop much power from the heat generated for used/spent fuel in the pools. On the other hand, one could produce hot water and heat for several houses from the heat given off by one spent fuel assembly. However, spent fuel is considered 'special nuclear material', since it contains fissile and fertile isotopes in addition to fission products, in addition to being HLW, so one cannot simply purchase spent fuel for use in one's home. SNM/HLW requires approval and permits from the NRC and various state agencies, and most people are not qualified to take on the responsibility of possessing SNM or HLW.

    Prolonged use of spent fuel would require some level of assurance that over the course of the use, the cladding integrity would not be compromised such that fission products would be released to the immediate systems, e.g., one's habitat, or to the environment. Most people probably wouldn't want to bother with the necessity of a formal program to ensure that cladding integrity or control of fission products is maintained.
     
    Last edited: Feb 14, 2015
  21. Feb 14, 2015 #20
    Thanks for your informative comment. It's nice to have a number giving me some idea of what kind of energy the energy spent fuel can give off. I'm curious, for how many years does it produce 1% of the energy that the fission process produces?

    What really interests me is the possibility of portable power sources for things like ships and mining operations. Do you think you could power a cargo ship with something like Strontium 90, and if you could do you think it could be economical and allowed?
     
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