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How far off is thorium energy?

  1. Aug 28, 2012 #1
    Evening all,

    In your opinions and based on your knowledge, how far in the future in terms of years do you think it is before thorium reactors will overtake uranium reactors of today, if at all?

    Is thorium going to kill the uranium energy or will it not even come close?

    Any views on this will be greatly appreciated.

    Many thanks
     
  2. jcsd
  3. Aug 28, 2012 #2

    etudiant

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    Thorium reactors is too broad a concept, as it covers the gamut from new fuel for existing reactors to existing design reactors optimized for thorium to new reactor designs such as the various molten salt thorium reactors.
    Thorium fuel bundles formulated to perform in existing uranium reactors have been developed in Russia and proposed for use as well in the US.
    The Canadian CANDU heavy water moderated reactors will run very happily on thorium fuel with minimal adjustments.
    However,afaik no one has built a large scale molten salt thorium demonstrator, so that route is at least a decade from opening up and meanwhile uranium is fairly abundantly available at low prices.
    Given these reasons, I think it will be many decades before thorium overtakes uranium as a reactor fuel.
     
  4. Sep 17, 2012 #3
    Thorium Fuel Cycle to be or not to be!

    Hi there,
    What's your opinion about using Thorium as fuel in current nuclear reactors.
    is it possible? is it economic?
    What's the different in terms of physical behaviors in reactor core?
     
  5. Sep 17, 2012 #4

    QuantumPion

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    Re: Thoruim Fuel Cycle to be or not to be!

    Thorium is not fuel, it is only used as feed material to make U-233 in a breeder reactor.

    If you wanted to you could fuel a conventional light water reactor with mixed oxide Th-232 plus U-233/U-235/Pu-239. In fact the Shippingport reactor operated as a thorium breeder for a period. However, LWR's are not particularly well suited for breeding as it is difficult and expensive to reprocess the fuel, and the breeding ratio is not much over 1 making it uneconomical to do so with current uranium prices.
     
  6. Sep 18, 2012 #5
    Re: Thorium Fuel Cycle to be or not to be!

    As I know both South-Korea and Russia have some projects about mixed-thorium fuel for existing reactor types. But judged from the frequency of relevant publications it'll be some years (a decade, maybe) before they can start the licensing of the reactors for their new fuel.
     
    Last edited: Sep 18, 2012
  7. Sep 20, 2012 #6

    Astronuc

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    In India, "so far about one tonne of thorium oxide fuel has been irradiated experimentally in PHWR reactors and has reprocessed and some of this has been reprocessed, according to BARC. A reprocessing centre for thorium fuels is being set up at Kalpakkam."

    Ref: http://www.world-nuclear.org/info/inf53.html

    See also - http://www.world-nuclear.org/info/inf62.html

    With uranium prices so inexpensive, utilities use UO2 fuel.

    The VVER and AHWR are well suited for a thorium cycle.
     
  8. Sep 21, 2012 #7

    mheslep

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    Re: Thoruim Fuel Cycle to be or not to be!

    I believe the Th reactor advocates are counting on reprocessing to be inexpensive. In any case it won't be free, so there has to make-up somewhere: enrichment largely goes away, high pressure vessel goes away for a liquid fuel/salt design. What else? Maybe containment goes away without the chance that high pressure primary side water can flash to steam?
     
  9. Sep 21, 2012 #8

    mheslep

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    A relevant question here is what is the price of enriched uranium since enrichment is not required for Th.
     
  10. Sep 24, 2012 #9

    Astronuc

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    Some amount of fissile material (U-235 or Pu-239) is required to obtain a critical configuration, even if it is natural uranium. The lower the enrichment, the lower the burnup and the lower the conversion of Th-232 to U-233.

    Thorium based fuels are invariably MOX, but (U,Th)O2 or (Pu,Th)O2, rather than (U,Pu)O2.

    There have been various studies related to Th-based fuel for Pu disposition, e.g.,
    Performance of Thorium-Based Mixed Oxide Fuels for the Consumption of
    Plutonium in Current and Advanced Reactors
    http://www.inl.gov/technicalpublications/Documents/2808461.pdf [Broken]

    from http://www.world-nuclear.org/info/inf63b_china_nuclearfuelcycle.html

    The thorium fuel cycles in India and China have adopted conventional methods as opposed to MSR type systems.
     
    Last edited by a moderator: May 6, 2017
  11. Sep 24, 2012 #10
    Why mixed?

    You´d want to expose the thorium only ever to well moderated neutron flux, because otherwise the fast neutrons fresh out of a fission event could cause (n,2n) reactions leading to uranium 232 (after two betas and neutron capture). It would also help to pick thorium which geologically is clean of ionium.
     
  12. Sep 24, 2012 #11

    mheslep

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    I had read India was exploring conventional solid fuel thorium reactors, but that China was investigating liquid fuels. From your link:

     
  13. Sep 24, 2012 #12

    QuantumPion

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    Re: Thoruim Fuel Cycle to be or not to be!

    These statements are pertinent to liquid thorium fast reactors. LTFR's continuously reprocess their fuel and due to the fast neutron spectrum have a higher breeding ratio. They still need high enriched U or Pu feed to get started though. The previous poster was asking about using Th in a convention LWR however.
     
  14. Sep 24, 2012 #13

    mheslep

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    Re: Thoruim Fuel Cycle to be or not to be!

    Sure, as Astronuc also pointed out.

    The salient point is that a liquid Th reactor would need a small, small fraction of the enriched U required by a conventional light water U reactor, and perhaps only at the first start up with no more ever required theoretically for the life of the reactor. In a world where liquid salt (or solid?) Th replaces U reactors the enrichment industry does not disappear, but it does slowly collapse to a shadow of its current self. Agents performing any additional enrichment would be clearly announcing they do so for one purpose - a weapon.
     
  15. Sep 24, 2012 #14

    Astronuc

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    As far as I know, the MSR is on paper, and it is certainly non-conventional.

    Ideally, one would start with a minimal enrichment (from U-235) and then gradually introduce U-233 as it is produced.

    There are certain design and performance issues to be resolved. One is homogeneity or variations of enrichment/reactivity (reactivity and power distribution), especially if there are multiple streams feeding the core, and in particular, if one stream goes offline.

    I see another critical issue being the loss of longer-lived delayed neutrons with the introduction of feed without delayed neutrons. It could make reactivity control a bit of a challenge under certain conditions.
     
  16. Sep 24, 2012 #15

    Astronuc

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    One needs a fissile source to begin (and control) the process. Reactivity control and stable power distribution are two basic requirements.

    One should look at the threshold for n,2n in Th-232. It's about 6.8 MeV, and only reaches 1 b at 7.7 MeV - toward the tail end of the fission neutron energy distribution.

    U and Th ores are cleaned of decay products.
     
  17. Sep 25, 2012 #16
    Only elements.

    Uranium inevitably contains decay product uranium II. Thorium inevitably contains decay product radiothorium.

    If an ore contains a mixture of uranium and thorium then purified thorium also contains uranium decay products uranium X1, ionium, uranium Y and radioactinium. While uranium X1, uranium Y and radioactinium rapidly decay once uranium has been removed, ionium is long lived.
     
  18. Sep 25, 2012 #17

    Astronuc

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    Please use modern terms for nuclides.

    http://www.alphacounting.com/Th_Decay_Series.html
    http://www.evs.anl.gov/pub/doc/Thorium.pdf [Broken]

    http://www.alphacounting.com/U_decay_series.html

    Note the long half-lives of U-238 and Th-232. I know from experience that the U-234 content of natural uranium is quite low. In enriched uranium, it is also quite low, as is the activity. I have handled natural and enriched UO2, and one task in a previous job was to verify the isotopic content of enriched U.

    The content of Th-229 and 230 is less than 1% each, and the Th-232 content is generally greater than 99%. Other elements are separated from Thorium and Uranium.

    Additional background: http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/radser.html
     
    Last edited by a moderator: May 6, 2017
  19. Sep 25, 2012 #18
    Since the halflife of uranium 234 is 18 000 times shorter than that of uranium 238, obviously its content is quite low. But since each uranium 238 nucleus decays into uranium 234 nucleus, uranium 234 activity is not low - it is necessarily equal to uranium 238 activity, and much bigger than uranium 235 activity. It increases further on enrichment.

    Thorium 229 is not found in nature, because it belongs in neptunium series. The second longest lived thorium isotope, thorium 230, has halflife about 200 000 times shorter than thorium 232, so thorium with under 99 % thorium 232 would be quite hot.
     
  20. Oct 4, 2012 #19

    Astronuc

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    FYI - Th/U-233 Multi-recycle in Pressurized Water Reactors: Feasibility Study of Multiple Homogeneous and Heterogeneous Assembly Designs
    http://rpd.ans.org/presentations/2010_W/Thorium_Reactor_Physics/1-ans010-w-di-yun-thorium-r1.pdf [Broken]
     
    Last edited by a moderator: May 6, 2017
  21. Oct 4, 2012 #20

    mheslep

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    The long lived radiotoxicity of waste problem disappears (slide 9), with very little Pu and no Am created. No enrichment fuel cycle.

    Apparently solid fuel Th in PWR's are receiving the focus, carrying along the problems of water flashing to steam and uncovered cores, as opposed to the molten fuel approach. I see the study was 2010, pre Fukushima.
     
    Last edited by a moderator: May 6, 2017
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