What are Fission Recoil Fragments and How Are They Formed?

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Discussion Overview

The discussion revolves around the concept of fission recoil fragments, their formation, and their characteristics in the context of nuclear fission. Participants explore the nature of these fragments, their behavior when interacting with materials, and comparisons between different radioactive elements.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants inquire about the definition and formation of fission recoil fragments and how they differ from other ionizing particles.
  • One participant suggests that fission fragments may be similar to alpha particles in that they can be reflected by materials like aluminum.
  • Questions arise regarding the concept of an absorption curve and whether different radioactive elements, such as U-235 and plutonium, ionize mass differently.
  • Another participant proposes that the recoil fragments are the remnants of the nucleus that are expelled during the fission process.
  • There is a discussion about the characteristics of fission fragments from U-236 and Pu-240, noting similarities and differences in their behavior.
  • One participant mentions a bimodal distribution of fission products when plotting yield versus atomic mass, indicating that the fissile nucleus splits into two distinct nuclei.

Areas of Agreement / Disagreement

Participants express various viewpoints regarding the nature and behavior of fission recoil fragments, with no consensus reached on the specifics of their formation or characteristics. Multiple competing views remain on how these fragments interact with materials and their ionization properties.

Contextual Notes

Some discussions involve assumptions about the behavior of fission fragments in different materials and the implications of their mass and charge, which may not be fully resolved.

RADboy
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i know the key word is "recoil" but, I'm reading a nuclear fission book and it keeps bringing up "fission recoil fragments" "recoil particles" what exactly are these particls? how are they formed? are they different from other ionizing particles other than the fact that they recoil?

A scientist was using thin sheets of aluminum (.57mg/cm thcik) to reflect the particles of neutron bombarded uranium. by measuring the radioactivity in each sheet he obtained a rough absorption curve 2.2+/- .2
 
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Well alpha particles are reflected by foils, so I suspect fission fragments are recoiling from the Al plate. Some will travel into the plate.

Look at Ernest Rutherford's experiments on the scattering of alpha particles at high angles.
 
what's absorption curve? depending on the radioactive element can the particles ionize masses differently? does U-235 ionize mass differently than plutonium?
 
RADboy said:
what's absorption curve? depending on the radioactive element can the particles ionize masses differently? does U-235 ionize mass differently than plutonium?
They could be looking for Linear Energy Transfer rate or distance that a fission product travels in a medium.

The fission fragments of U-236* and Pu-240* (* = composite nucleus after neutron absorption) are about the same. The lower mass population shift upward by Z=1, A=2 somewhat. The complementary pairs are different.

In UO2 or MOX, the fission tracks are about 3-6 microns, while in Al, they should be greater because the Al atom is lighter.
 
RADboy said:
i know the key word is "recoil" but, I'm reading a nuclear fission book and it keeps bringing up "fission recoil fragments" "recoil particles" what exactly are these particls? how are they formed? are they different from other ionizing particles other than the fact that they recoil?

I think the recoil fragments are the pieces of the nucleus left over that recoil away from the emitted neutrons and alpha particles?
 
"The fission fragments of U-236* and Pu-240* (* = composite nucleus after neutron absorption) are about the same. The lower mass population shift upward by Z=1, A=2 somewhat. The complementary pairs are different."


what exactly do you mean by the lower mass populatin shift upward by Z=1, A=2?
 
RADboy said:
"The fission fragments of U-236* and Pu-240* (* = composite nucleus after neutron absorption) are about the same. The lower mass population shift upward by Z=1, A=2 somewhat. The complementary pairs are different."


what exactly do you mean by the lower mass populatin shift upward by Z=1, A=2?

When plotting yield vs atomic mass, one see a two hump/peak (bimodal) distribution, because the fissile nucleus splits into two nuclei.

http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/u235cs.html#c1

http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/u235chn.html

http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/fisfrag.html
 

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