What is the difference between Nuclear Fission and Fusion?

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Discussion Overview

The discussion explores the differences between nuclear fission and fusion, focusing on their mechanisms, energy sources, and conditions required for each process. Participants share basic definitions and delve into the complexities of nuclear reactions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant seeks clarification on the differences between fission and fusion, indicating a beginner's interest in nuclear science.
  • Another participant provides links to Wikipedia articles on fission and fusion for additional reference.
  • A participant defines fission as the splitting of a heavy nucleus (e.g., U-235) into smaller nuclei, while fusion is described as the combining of lighter nuclei (e.g., deuterium and tritium) to form a larger nucleus.
  • It is noted that both processes release energy due to the mass difference between the reactants and products.
  • Fission is characterized by the splitting of unstable, high atomic number atoms, which results in radioactive byproducts, and can occur at room temperature under the right conditions.
  • Fusion involves the combination of low atomic number atoms into more stable forms, requiring high energy to overcome the Coulomb force, thus making it difficult to achieve under normal conditions.
  • A mention of low energy nuclear reactions (LENR) is made, suggesting they are speculative and not widely accepted, with a comparison to historical perceptions of chemistry.

Areas of Agreement / Disagreement

Participants present various definitions and explanations of fission and fusion, but there is no consensus on the viability or acceptance of LENR as a legitimate process. The discussion remains exploratory without definitive conclusions.

Contextual Notes

Some assumptions about the stability of nuclei and the conditions for fusion may not be fully explored. The discussion includes speculative ideas about LENR that lack broad acceptance in the scientific community.

DrPosh
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Just curious, I am new to learning about nuclear science and would like to know some differences between Fission and Fusion. Thanks in advance!

-Posh
 
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Fission is when a heavy nucleus (such as U-235) splits into smaller nuclei. Fusion is when lighter nuclei (such as deuterium and tritium) combine to make a larger nucleus.
 
Both get their energy from the difference in mass between the fuel and the end products.

Fission breaks apart very high atomic number atoms, which are naturally unstable. The pieces are medium atomic number, but these pieces have many extra neutrons for their number of protons, and are thus very radioactive. The fission reaction is caused by a neutron colliding with the unstable nucleus, so there is no minimum energy, and fission can and does occur at room temperature, in the proper setup.

Fusion combines two very low atomic number atoms, into more stable versions, such as Hydrogen into Helium. The targets of fusion are often "magic", that is they are somewhat like a ball made of smaller balls that Tesselate nicely in 3D. These fusion targets show on a graph of binding energy per nucleon as a tall spike... He4, O16, and so on. Because the point of fusion is getting atomic nuclei with charge to collide, it requires the atoms move fast enough to overcome the natural repulsion of the Coulomb force long enough for the strong force to interact. This means fusion cannot occur under normal circumstances.

The third possibility for nuclear energy is to make combinations of medium atomic number isotopes with a light isotope, a so-called "low energy nuclear reaction." This is about as believable as alchemy, but so was chemistry at one point. There is some talk about using neutrinos to temporarily cause hydrogen to turn into a neutron, for instance. LENR would be cool if it was real, but right now it just makes for good Science Fiction.
 

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