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About Doppler coefficient

  1. Jun 29, 2012 #1
    hello,everybody .Doppler coefficient will be positive?
     
  2. jcsd
  3. Jul 2, 2012 #2
  4. Jul 2, 2012 #3

    Astronuc

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    Whether the Doppler coefficient (for resonance absorption) is positive or negative depends on the composition of the fuel/core.

    If resonance absorption leads to more (n,γ) and less fission then it has a negative effect on reactivity in a critical system.

    If the absorption leads to more fission and less (n,γ), then it has a positive effect.


    In an LWR (water moderated reactor) the Doppler coefficient is negative. The U-238 resonances absorb neutrons more readily, and to some extent, the resonance absorption of U-235 and Pu-239 resulting in (n,γ) compete with those resulting in fission.

    Some fast and intermediate spectrum reactors may have a positive Doppler coefficient with certain configurations. Such configurations are to be avoided.

    References:
    http://www.barc.gov.in/publications/eb/golden/reactor/toc/chapter1/1_1.pdf
    http://www.inl.gov/technicalpublications/Documents/4502642.pdf [Broken]
     
    Last edited by a moderator: May 6, 2017
  5. Jul 5, 2012 #4
    thank you very much
     
    Last edited by a moderator: May 6, 2017
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