Where do the initial neutrons come from?

In summary, the atomic bomb is created when two hemispheres of fission material, either Uranium or Plutonium, are joined together with conventional explosives. The initial neutrons needed to trigger the fission reaction come from the Uranium or Plutonium themselves, but it is usually more reliable to use a separate neutron source.
  • #1
Eagle9
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In atomic bomb there are two hemispheres of fission material (Uranium or Plutonium), they are joined by means of conventional chemical explosives, the necessary critical mass is reached and the atomic bomb explodes, everybody knows this:
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But is this condition enough? Indeed, the initial neutrons are needed to trigger the fission reaction, where do these neutrons come from? Definitely not from the Uranium or Plutonium………….:rolleyes:
 
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Yes, the Uranium or Plutonium have a low level of spontaneous fission happening all the time that may provide the neutrons needed to initiate the chain reaction. It is possible in theory, but in practice it works better to have a separate more reliable neutron source such as a Polonium-Beryllium alloy. The Polonium provides alpha particles and the Beryllium converts them into neutron radiation.
 
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  • #3
Actually, Plutonium produces too many neutrons from spontaneous fission for this design. The reaction would start too early and the pieces would repel each other before most of the material was used.

Therefore, all Plutonium bombs (and all current bombs in general) implode a hollow ball and have a separate neutron source - that is faster and more reliable.
 
  • #4
dauto said:
Yes, the Uranium or Plutonium have a low level of spontaneous fission happening all the time that may provide the neutrons needed to initiate the chain reaction. It is possible in theory, but in practice it works better to have a separate more reliable neutron source such as a Polonium-Beryllium alloy. The Polonium provides alpha particles and the Beryllium converts them into neutron radiation.

I hate to intrude on someone else's topic and ask questions but would you mind explaining how Beryllium converts Alpha particles into Neutrons, does it somehow capture the protons?
 
  • #5
delsaber8 said:
I hate to intrude on someone else's topic and ask questions but would you mind explaining how Beryllium converts Alpha particles into Neutrons, does it somehow capture the protons?

See this article on Beryllium: 'Nuclear Properties'

http://en.wikipedia.org/wiki/Beryllium

The part of a nuclear device which furnishes the initial neutrons to start the fission reaction is called an 'initiator'. The initiator for the first atomic bombs was made by smashing Polonium and Beryllium together when the bomb was detonated. The neutrons produced by the initiator then stuck the fissile uranium or plutonium fuel and started the chain reaction.

When a Be-9 nucleus is struck by an energetic alpha particle produced by the decay of Polonium, the alpha particle fuses with the beryllium nucleus to produce a carbon-12 nucleus plus a neutron.

Later designs of initiators cause a few atoms of deuterium and tritium to fuse by use of high-voltage electrical current to generate neutrons.

http://en.wikipedia.org/wiki/Neutron_generator
 
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  • #6
dauto
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SteamKing
Thanks guys :smile:
 

1. Where do initial neutrons come from?

Initial neutrons are believed to come from the process of nucleosynthesis, which occurs in the cores of stars. During this process, hydrogen atoms fuse together to form heavier elements, releasing energy in the form of neutrons.

2. Are initial neutrons created in nuclear reactions?

No, initial neutrons are not created in nuclear reactions. They are already present in the nuclei of atoms and are released during nuclear reactions, such as fission or fusion.

3. Can initial neutrons be artificially created?

Yes, initial neutrons can be artificially created through processes such as nuclear reactions or particle accelerators. These methods are used in scientific research and nuclear technology.

4. How do initial neutrons contribute to nuclear energy?

Initial neutrons are crucial to the process of nuclear energy. In nuclear reactors, the neutrons released during fission reactions are able to collide with other atoms, causing a chain reaction and releasing large amounts of energy.

5. Are initial neutrons stable particles?

Initial neutrons are not considered to be stable particles. They have a half-life of about 15 minutes and can decay into other particles, such as protons and electrons.

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