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India's thorium reactor delayed

  1. Aug 23, 2014 #1

    jimgraber

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  2. jcsd
  3. Aug 24, 2014 #2

    etudiant

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    A serious accident with a large sodium cooled reactor would be a nightmare worse than Fukushima.
    Unfortunately, sodium cooled reactors are very unforgiving, as France, Japan and the US have all discovered.
    Imho we have been lucky that none of the breakdowns that have taken place have been catastrophes.
    It might be more useful for India to use its rich human capital to solve the technical problems standing in the way of a molten salt thorium reactor than to pursue this three time loser concept.
     
  4. Aug 24, 2014 #3

    jimgraber

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    Molten salt based Thorium reactors:
    Not being an expert or even particularly well-informed, I googled some more, and discovered that the Indians, the Chinese and even some US companies are at least talking about molten salt thorium reactors. I didn't find any project expected to be completed before 2017 or later, however. Did I miss one?
    Jim Graber
     
  5. Aug 24, 2014 #4

    etudiant

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    The molten salt thorium reactor is seductively simple in concept, but has never been demonstrated on a commercial scale, although a small proof of concept unit was run for years at Oak Ridge. The design has issues, notably the need to flush unwanted nuclear reaction products near continuously, but otherwise seems more forgiving than the sodium cooled options. It may be seen as 'the road not taken' in the nuclear power industry.
     
  6. Sep 29, 2014 #5
    Russia has been running the BN 600 reactor since 1980, successfully. And is in the process of starting a BN 800 reactor.
    They also have a BN 1200 reactor in planning. They had also been operating a BN 350 reactor for electricity, desalination and Pu production from 1964 till 1992. So obviously the technology can be managed.
    The US sodium reactor was shut down by politicians not by technicians. The people that were involved thought it was a great success. Having said that, I am not very fond of the idea of a flammable or even explosive coolant.
    Russia also intends to "fire" up a small lead cooled reactor in 2017.
     
  7. Sep 30, 2014 #6
    It is a success until the first meltdown. A sodium-cooled fast reactor's meltdown has all ingredients to be many times worse than Chernobyl, likely dooming the nuclear industry.

    Exactly.
     
  8. Sep 30, 2014 #7

    Doug Huffman

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    Wasn't Japan's Monju a sodium cooled fast reactor? I
     
  9. Sep 30, 2014 #8

    etudiant

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    The successful operation of a reactor is not sufficient, it is essential that the possibility of stupid mistakes be allowed for.
    Idiot proof is really what is needed. That is a very stiff hurdle, especially as the insides of a reactor in full cry is a difficult environment, a near eruption of very hot pressurized fluids that are under tenuous control. The USAF Timberwind reactor project failed at the proof of principle stage when the coolant gas experienced a partial blockage because of a failed component, much as the Fermi reactor was nearly destroyed because the sodium coolant flow was blocked by a loose piece of cladding. The German pebble bed reactor project died because the night shift operators tried to clear a blockage in the feeder tube carrying the uranium fuel pellets by banging on the carbon clad fuel with a broomstick, destroying the fuel integrity and contaminating the site.
    Stuff happens and the nuclear industry will not thrive until it recognizes that and operates accordingly.
     
  10. Oct 6, 2014 #9

    mheslep

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    The MSR concept does not necessarily need to continuously flush fission products any more than a solid fueled reactor. The *ability* to remove fission products on the fly from liquid fuels is an option, an advantage that enables high burn-up.
     
  11. Oct 6, 2014 #10

    Astronuc

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    While technically that is correct, I can't imagine a licensing authority approving such a design. If the core average burnup was say 20 GWd/tHM, then 2% of the volume would be fission products, and some fission products can lead to embrittlement of structural alloys.

    With solid fuel, most of the fission products are trapped in the solid oxide matrix, although some fission gas (isotopes of Xe, Kr) do escape into the rod internal void volume. Also, some of the volatiles, Cs, I, Te, Br, will also find their way to the cooler regions of the ceramic fuel or cladding.

    In the case of certain metal fuels, one problem has been fuel (fission product)-cladding chemical interaction, so in an MSR, there is the potential for fission-product interaction with the structural materials, particularly at high temperatures.

    One has to be concerned about eutectics and liquid metal embrittlement.
     
  12. Oct 7, 2014 #11

    mheslep

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    Does this concern stem from assuming the requirements for a PWR, i.e. a 300 atm pressure vessel, holding water and subject to N-16 gamma, or the case of the structural vessel appropriate for a molten salt reactor with only ρgh pressure, no water?

    The reports on the MSR experiment at ORNL using U-233 indicate they removed only noble gasses (i.e. Xe) with a spray system leaving the rest of the fission products in place. I'm uncertain of the percent by volume of the fission products, but I suspect they'd be much lower than you indicate since the total salt volume is much greater than that salt inside the core at any one time, unlike the case of solid fuel reactor. The reports I've read from ORNL and interviews with the MSR engineers indicate some unresolved concerns about Hastelloy-N in contact with the flourine from the salt, but not from any fission products.

    http://en.wikipedia.org/wiki/Molten-Salt_Reactor_Experiment#Results
     
    Last edited: Oct 7, 2014
  13. Oct 7, 2014 #12

    Astronuc

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    Normal pressure in a PWR primary system is about 157 atm, and trip point is higher, may be about 194 atm, and probably less than 200 atm. The containment is even lower ~6 atm, based on the volume and cooling systems.

    The concern from an MSR is keeping the fluid fuel where the design intends it to be as opposed to flowing out a break in the pipe where it is not intended to go.
     
  14. Oct 8, 2014 #13

    mheslep

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    Yes, certainly fuel needs to be contained. The issue, brought up by questioning the impact of fission products on the reactor vessel, is what are the requirements of the structural vessel relative to, say, a traditional PWR vessel, in the presence of fission products. There is experience on the topic, via the years of zirc-alloy tubing containing oxide fuel and thus products, and then the early experience with Hastelloy-N in the MSR experiment which did not remove fission products (save noble gasses).
     
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