What is the Doppler coefficient and how does it affect wave frequency?

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Discussion Overview

The discussion centers around the concept of the Doppler coefficient, particularly in the context of resonance absorption in nuclear reactors. Participants explore how the Doppler coefficient affects wave frequency and reactivity, with a focus on different reactor types and fuel compositions.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants inquire whether the Doppler coefficient is always positive.
  • It is proposed that the sign of the Doppler coefficient depends on the composition of the fuel/core, with resonance absorption potentially leading to either positive or negative effects on reactivity.
  • In light water reactors (LWR), it is stated that the Doppler coefficient is negative due to U-238 resonances absorbing neutrons more readily.
  • Some configurations in fast and intermediate spectrum reactors may exhibit a positive Doppler coefficient, although these configurations are suggested to be avoided.

Areas of Agreement / Disagreement

Participants express differing views on the conditions under which the Doppler coefficient may be positive or negative, indicating that multiple competing perspectives remain unresolved.

Contextual Notes

The discussion highlights the dependence of the Doppler coefficient on specific reactor configurations and fuel compositions, which may not be universally applicable.

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hello,everybody .Doppler coefficient will be positive?
 
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googlefans said:
hello,everybody .Doppler coefficient will be positive?
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
 
Last edited by a moderator:
Astronuc said:
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

thank you very much
 
Last edited by a moderator:

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