Binding energy or Kinetic energy?

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Discussion Overview

The discussion revolves around the concepts of binding energy and kinetic energy in the context of nuclear fusion, specifically the fusion of deuterium and tritium into helium-4. Participants explore the relationship between mass defect, binding energy, and the energy released during fusion processes.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant expresses confusion about the distinction between binding energy and released energy, particularly in relation to mass defect during deuterium-tritium fusion.
  • Another participant discusses the concept of binding energy in different materials, such as uranium and concrete, suggesting a relationship between kinetic energy and binding energy.
  • A later reply clarifies that mass defect is not directly spent on changing binding energy but is related to the difference in binding energy, which is then emitted as kinetic energy or radiation.
  • Mathematical expressions are provided to illustrate the relationships between rest masses, binding energies, and released energy in the fusion reaction.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the relationship between binding energy and kinetic energy, and the discussion includes competing views and interpretations regarding mass defect and energy release in fusion processes.

Contextual Notes

Some participants mention specific scenarios, such as the operation of a Boiling Water Reactor (BWR) and a dedicated district heating reactor, but do not provide detailed explanations or conclusions about binding energy changes in these contexts.

A M
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Summary: I always confuse Binding Energy with Released Energy in such processes. Which one comes from mass defect?
For example in a Deuterium-Tritium fusion two nuclei with lower binding energy converse to He-4 with much higher binding energy (and a neutron). The released energy is 17.6 MeV.
What exactly happens to mass defect?
Is it conversed to the higher binding energy of ∝-particle
or the released kinetic energy of the products?

Anyone could help me with this problem?

1565138815307.png
Fusion of deuterium with tritium creating helium-4, freeing a neutron, and releasing 17.59 MeV as kinetic energy of the products while a corresponding amount of mass disappears, in agreement with kinetic E = Δmc2, where Δm is the decrease in the total rest mass of particles....This difference in mass arises due to the difference in atomic "binding energy" between the atomic nuclei before and after the reaction.

Isn't it a contrast?!:confused:
https://en.wikipedia.org/wiki/Nuclear_fusion
 
Last edited:
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Concrete has high chemical binding energy. Uranium has low binding energy, it's actually negative. When an atom bomb explodes above a city, the end result is that the uranium has gained more binding energy while the concrete has lost binding energy. The concrete gained mass, the bomb lost mass.

An asteroid can do the same thing as an atom bomb, because it has lot of kinetic energy.

What can we conclude now? Well, it seems that kinetic energy is negative binding energy. Or those two things are the same thing.

(Maybe I made a little bit too strong claim there, negative binding energy is potential energy, kinetic energy and potential energy are both energy, but different types of energy. )
For uranium: nuclear binding energy + electrostatic binding energy < 0

For concrete: total binding energy < 0 , but chemical binding energy is the only binding energy that changes in this particular scenario.

Questions:

A) What binding energy changes are occurring inside a BWR nuclear power plant? BWR = Boiling Water Reactor.

B) What binding energy changes are occurring inside a dedicated district heating reactor?
 
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A M said:
What exactly happens to mass defect?
Is it conversed to the higher binding energy of ∝-particle
or the released kinetic energy of the products?
You're confused because you're double counting. It's not that mass defect is spent on changing the binding energy - it is the difference in binding energy. More tightly bound means less massive. That difference is then emitted as kinetic energy or radiation.

So, let's say we have the reaction shown in the picture:
##m_d, m_t, m_h, m_p, m_n## - rest masses of deuterium, tritium, helium, isolated proton, and isolated neutron respectively.
##E## - released energy
##B## - binding energy

now:
##m_d=m_p+m_n-B_d##
##m_t=m_p+2m_n-B_t##
##m_h=2m_p+2m_n-B_h##

and the fusion reaction is:
##m_d+m_t=m_h+m_n+E##

here we could write:
##m_d+m_t-m_h-m_n=E##
##\Delta m=E## (*using natural units)
and conclude that all the energy comes from the difference in initial and final masses (mass defect),

or write:
##(m_p+m_n-B_d)+(m_p+2m_n-B_t)=(2m_p+2m_n-B_h)+m_n+E##
cancelling out all the rest masses of isolated nucleons we get
##-B_d-B_t=-B_h+E##
##-B_d-B_t+B_h=E##
##\Delta B=E##

So we can see that all the released energy comes from the difference between initial and final binding energies. It's the same thing, just more deeply understood.
 
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Bandersnatch said:
You're confused because you're double counting. It's not that mass defect is spent on changing the binding energy - it is the difference in binding energy. More tightly bound means less massive. That difference is then emitted as kinetic energy or radiation.

So, let's say we have the reaction shown in the picture:
##m_d, m_t, m_h, m_p, m_n## - rest masses of deuterium, tritium, helium, isolated proton, and isolated neutron respectively.
##E## - released energy
##B## - binding energy

now:
##m_d=m_p+m_n-B_d##
##m_t=m_p+2m_n-B_t##
##m_h=2m_p+2m_n-B_h##

and the fusion reaction is:
##m_d+m_t=m_h+m_n+E##

here we could write:
##m_d+m_t-m_h-m_n=E##
##\Delta m=E## (*using natural units)
and conclude that all the energy comes from the difference in initial and final masses (mass defect),

or write:
##(m_p+m_n-B_d)+(m_p+2m_n-B_t)=(2m_p+2m_n-B_h)+m_n+E##
cancelling out all the rest masses of isolated nucleons we get
##-B_d-B_t=-B_h+E##
##-B_d-B_t+B_h=E##
##\Delta B=E##

So we can see that all the released energy comes from the difference between initial and final binding energies. It's the same thing, just more deeply understood.
Thank you very much!
 

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