Critical fission energy question

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Discussion Overview

The discussion revolves around determining the fissility of a nucleus (A)Z based on its mass compared to a neighboring nucleus (A+1)Z and its critical fission energy. Participants explore methods for assessing whether (A)Z is fissile and under what conditions fission might occur.

Discussion Character

  • Homework-related
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant asks how to determine if (A)Z is fissile given the masses of (A)Z and (A+1)Z and the critical fission energy of (A+1)Z.
  • Another participant suggests comparing the binding energy of the compound nucleus (A+1)Z with the critical energy as a potential method.
  • A third participant proposes calculating the separation energy using the formula E = m(n) + m(A) - m(A+1) to assess fissility.
  • A later reply references the mass-energy difference between reactants and products, indicating that the energy released can manifest as prompt gamma or kinetic energy of products.
  • Participants mention calculating the mass-energy difference specifically between U235+n and U236 as an example.

Areas of Agreement / Disagreement

Participants present various methods and approaches without reaching a consensus on a single method for determining fissility or the conditions for fission.

Contextual Notes

The discussion includes assumptions about the definitions of fissility and critical fission energy, as well as the dependence on specific nuclear masses. The mathematical steps involved in the calculations remain unresolved.

andybham
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I have a fission exam next week, can someone help me with this past paper question:

If you know the masses of two nuclei (A)Z and (A+1)Z, (say masses are (A) and (A+1)) and you know the 'critical fission energy' of (A+1)Z, how do you determine if (A)Z is fissile? if it is not fissile, at what neutron energy would you expect fission to be possible.
 
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How about comparing the binding energy of the compound nucleus (A+1)Z with the critical energy?
 
is this done by calculating the separation energy? E = m(n) + m(A) - m(A+1)
 
http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/nucbin.html

E = (m(n) + m(A) - m(A+1)) c2
yes - it is the mass-energy difference between the reactants and product(s). The energy is released as prompt gamma or as the kinetic energy if there are two or more products.

Calculate the mass-energy difference between U235+n and U236.
 

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