Special Nuclear Reactions
1. Neutron Induced Fission
2. Fusion
3. Photonuclear Reactions
4. Heavy Ion Reactions
Neutron Induced Fission
• A neutron is captured by heavy nuclide to form a compound nucleus
• Compound nucleus then splits into two smaller fragments and emits two or three free neutrons along with 200 MeV of energy
• For low-mass nuclides, binding force >> Coulomb force, fission is not feasible
• For Heavy nuclides, binding force ≈ Coulomb force, addition of neutron shift the balance in favor of repulsive force
• Neutron provides some internal excitation energy that deforms the nucleus into a transition state
• Severe deformations, split the nucleus into two fragments
The fission process involves the deformation of a nucleus through a series of shapes like those shown in figure below
Low energy neutron: asymmetric fission
High energy neutron: symmetric fission
Fusion
• Non spontaneous on earth
• Spontaneous in sun and star
• Threshold reactions ( charged particle reaction)
• Fusion has several advantages over fission as a source of energy
• Unlimited deuterium from oceans
• The products of d-d and d-t fusion reactions are not radioactive
• No significant waste disposal problems
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These reactions take places using accelerators are not self-sustaining reactions, the require the continual input of energy to continue.
Photonuclear Reactions
• Induced by electro-magnetic radiation
• Threshold reactions
• Imparted low energy on target, emission ofone or two nucleons, (γ, n), (γ, 2n), (γ, p)
• Cross section usually on the order of millibarns
• Excitation functions show giant resonance
Heavy Ions Reactions
• Mass > 4He
• 12C6+, 40Ar8+, 84Kr30+, 235U50+
• High charge, formidable Columb barrier
• Deep inelastic reaction
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