Why prompt neutron gets less share of energy (fission)

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    Energy Fission Neutron
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Discussion Overview

The discussion revolves around the energy distribution in fission reactions, specifically why prompt neutrons receive less energy compared to fission fragments. Participants explore the implications of a formula related to energy distribution and the timing of neutron emission during the fission process.

Discussion Character

  • Technical explanation, Debate/contested

Main Points Raised

  • One participant questions why neutrons receive less energy in fission reactions compared to fission fragments, referencing a formula that suggests lower mass should result in a higher energy share.
  • Another participant clarifies that the formula in question is applicable only to decays involving two particles, noting that fission typically results in two or three parts, with neutrons being emitted subsequently.
  • A similar point is reiterated about the formula's limitations, emphasizing that the energy of prompt neutrons is approximately a few MeV, which is distinct from the energy of the fission fragments.
  • A participant raises a question about the timing of neutron emission, asking if neutrons are emitted simultaneously with fission.
  • Another participant responds that some neutrons are emitted later, and questions arise regarding the definition of when neutrons are considered part of the nucleus and the completion of the fission process.

Areas of Agreement / Disagreement

Participants express differing views on the applicability of the energy distribution formula and the timing of neutron emissions, indicating that the discussion remains unresolved with multiple competing perspectives.

Contextual Notes

The discussion highlights limitations in the application of the energy formula, the ambiguity in defining the fission process, and the timing of neutron emissions, which are not fully resolved.

Magnetic Boy
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why neutron get so little energy in fission reaction as compare to fission fragments?
according to formula
Em=Ef(M)/(m+M)
m=mass of small fragment
M= mass of relatively big fragment
Ef=fission energy
by the same logic neutron should get highest share due to their lower mass. i am missing something please point out. thanks
 
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That formula only works for decays to two particles. Fission splits the nucleus in two (rarely three) parts, those parts then emit neutrons. The decay energies of those processes are a few MeV - the energy of the prompt neutrons (to a good approximation).
 
mfb said:
That formula only works for decays to two particles. Fission splits the nucleus in two (rarely three) parts, those parts then emit neutrons. The decay energies of those processes are a few MeV - the energy of the prompt neutrons (to a good approximation).
are neutrons emit with fission simulatneously?
 
Some are clearly emitted later, for some the question becomes ambiguous - how long do you consider neutrons part of a nucleus, and when exactly is the fission process done? You don't have classical objects moving around.
 

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