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India and Thorium reactors progress

  1. Nov 25, 2009 #1
    I understand India has some of the world's largest supply of thorium, and that thorium reactors are the fast breeder type.

    How close is India to building a commercial thorium reactor and what other nations would benefit from thorium fission?
     
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  3. Nov 25, 2009 #2
    Actually, they are thermal breeders. This is what is unique about the U-233/Th-232 fuel cycle: unlike plutonium, you can achieve a positive breeding ratio (that is, a net increase in fissile atoms) with thermal (cold) neutrons. In India's nuclear program, they are designing heavy-water reactors (like CANDUs) to run on thorium. This is the "Advanced Heavy Water Reactor" (AHWR) design; I'm not sure how far advanced it is, but they have not built any yet. However, they have tried thorium fuel (partially) in existing HWRs, and they operate a pure-U233 research reactor (KAMINI), so there is substantial progress. According to information from India's nuclear power agency:

    http://www.dae.gov.in/publ/3rdstage.pdf [Broken]

    You may have been confused because they are separately developing a fast breeder program (the plutonium fuel cycle). This is further advanced; they are already building a commercial-scale, 500 MW sodium reactor.
     
    Last edited by a moderator: May 4, 2017
  4. Nov 25, 2009 #3

    mgb_phys

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    Isn't the problem with a thorium reactor that it doesn't produce Pu?
     
  5. Nov 26, 2009 #4

    Astronuc

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    The reduction of Pu and transplutonic elements is considered beneficial from a recycling and proliferation issue.

    Thorium fuel has been demonstrated in the Shippingport reactor.

    More at - http://www.world-nuclear.org/info/inf62.html

    Thorium fuel cycle — Potential benefits and challenges - http://www-pub.iaea.org/MTCD/publications/PDF/TE_1450_web.pdf
     
  6. Nov 26, 2009 #5

    mgb_phys

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    Unless you have nuclear armed neighbours on both sides of you that you have been more or less at war with for the last 50years
     
  7. Nov 26, 2009 #6

    Astronuc

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    I think India already has a viable nuclear weapons program from their PHWR. One only needs a few production reactors. Each single Pu weapon needs on the order of 10 kg, so 1 MT provides about 100 warheads. These can be in the kT range or enhanced to MT range with the appropriate thermonuclear package.

    IIRC, the US and Russia each have about 50 to 60 MTHM of highly enriched (WG) U and Pu. A lot of WGU has been downblended and is being consumed in US reactors. There is a plan to dispose of the WGPu by downblending it and consuming it in LWRs as MOX.

    Besides, I seem to remember that one can make a nuclear weapon from U-233, but that Pu-239 is more optimal.
     
  8. Nov 26, 2009 #7

    mgb_phys

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    Yes I was rather cynically assuming that India's nuclear program was to fuel weapons development rather than to meet it's power needs.
    I suppose if it has a lot of thorium but no uranium reserves it might be a good strategic move. They are busy doing a deal with Canada to buy uranium - their earlier dealings having been forgiven.

    You should be able to make a device with U233 - so it's possibly more of a proliferation risk than the more optimal but trickier Pu. Don't know if a U233 gun is as simple as a U235 - but everybody attempting a Uranium gun device seems to have got it right first time.
     
  9. Nov 26, 2009 #8

    Astronuc

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    I believe they have a lot more thorium and little uranium or perhaps poor quality U. The thorium fuel cycle requires a fissile driver. In the Shippingport fuel, the thorium was mixed with U-235. The U-235 was necessary to provide the initial fissions. Over time, Th-232 is converted to U-233, and then U-233 becomes the principle fission material.

    Pu systems are smaller and yields higher (better for multiple (cluster) warhead systems), and they make for better triggers for thermonuclear weapons.
     
    Last edited: Nov 27, 2009
  10. Nov 26, 2009 #9

    mgb_phys

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    True for an advanced nuclear program like India's.
    I was just thinking that Pu is regarded as the proliferation risk while for an 'unofficial' nuclear power U 235 is a lot easier - and I'm guessing that fissile U233 is similair.
     
  11. Nov 29, 2009 #10
    I see that Thorium is 3x more plentiful than uranium


    are there other fertile element more plentiful than uranium?
     
  12. Nov 29, 2009 #11

    Astronuc

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    Thorium and uranium are it. They are the only elements which have very long half-life isotopes Th-232 and U-238, which can produce fissile isotopes with neutron absorption (and subequent beta decays), U-233 and Pu-239, and U-235 which is fissile and has a relatively long half-life. Heavier isotopes are more radioactive, i.e. have shorter half-lives and have decayed away long ago. Elements from Bi up through Ac are radioactive, or do not have fertile isotopes. Bi-209 is considered stable (the only stable isotope of Bi), although there is some experimental evidence that it has a very long half-life >> Th232 or U238.
     
  13. Nov 29, 2009 #12
    thanks. So India is nearest to a working Thorium reactor? thanks in advance
     
  14. Nov 29, 2009 #13

    Astronuc

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    The US has already done thorium fuel in the Shippingport PWR, and there are academics who have done work in this area. I believe the Russians, and perhaps Chinese, have looked at it.

    Indian Point 1 was supposed to use thorium fuel, which it did in the first core. But apparently it didn't work as expected, and the plant was subsequently shutdown in October 31, 1974 because of a number of technical problems (not related to thorium).
    http://www.americanscientist.org/issues/feature/thorium-fuel-for-nuclear-energy/1

    India is perhaps farthest along in commercial implementation. US, Russia and China have adequate resources to use the more conventional enriched U in LWRs. Canada, of course, has CANDU, heavy water plants that use natual or slightly enriched U in UO2.


    This might be of interest - http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/radser.html
     
    Last edited: Nov 30, 2009
  15. Dec 8, 2009 #14
  16. Dec 8, 2009 #15

    mgb_phys

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    But not really a practical fuel, you have to make it from Pu
     
  17. Dec 8, 2009 #16
    You're right, it is not a primary energy source. However, it could be potentially used to fuel a reactor, and certainly counts when listing fissile material.
     
  18. Dec 8, 2009 #17

    mheslep

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    The problem with U233 is that it has a hard gamma emitter somewhere in its decay chain, so anyone attempting to make a weapon out of it is likely going to dangerously expose themselves and certainly give the weapon reliability problems. So while this likely rules out U233 use for a large weapons program by a nation, it might not be hard roadblock for a one bomb terrorist group.

    Edit: I see that emitter is Tl 208 - all detailed in the IAEA paper Astronuc linked to:
    https://www.physicsforums.com/showpost.php?p=2460821&postcount=4
     
    Last edited: Dec 9, 2009
  19. Dec 9, 2009 #18

    Astronuc

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    Am-242m is not practical for commercial fuel because of it's radioactivity and that of the other transuranics. The trans-Pu isotopes are problematic for MOX fuel made from recycled/reprocessed commercial fuel.

    To use U-233 for a weapon, it would have to be 'cleaned' during the Thorex process.
     
  20. Dec 9, 2009 #19

    mheslep

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    As a practical matter, I have no doubt that is true for the reasons stated above. But would it be true for a small group of fanatics who got their hands 10kg?
     
  21. Dec 9, 2009 #20

    Astronuc

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    It would not be practical for a small group of fanatics to steal spent fuel. Any spent fuel whether UO2, ThO2, or MOX would have to reprocess the oxide, separate the fission products and non-fissile fuel, and convert the U-235, Pu-239, or U-233 to metal. That's not a garage or kitchen type of operation.

    Deliberately making Pu-239 or U-233 optimally for weapons use requires another deliberate approach.
     
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