Nuclear Processes: Fission and Fusion

Nuclear Reactions

• Nuclei can join (fuse) or split (fission).
• Crucial in nuclear chemistry.

Radioactive Decay (Review)

• Alpha Decay:
  • Emission of a helium nucleus.
  • Atomic mass decreases by 4.
  • Atomic number decreases by 2.
• Beta Decay:
  • Beta Plus Decay: $p \rightarrow n + e^+$
    • Atomic mass unchanged.
    • Atomic number decreases by 1.
  • Beta Minus Decay: $n \rightarrow p + e^-$
    • Atomic mass unchanged.
    • Atomic number increases by 1.

Nuclear Fission

• Heavy nucleus splits into smaller, more stable nuclei.
• Releases large amounts of energy.
• Example: Neutron + Uranium-235.
• Produces radioactive waste.
• Chain Reaction: Self-sustaining fission propagated by neutrons.
  • Requires critical mass.

Nuclear Fusion

• Lighter nuclei combine to form a heavier, more stable nucleus.
• Releases energy.
• High activation energies.
• No radioactive waste.
• Example: Hydrogen-2 + Hydrogen-3 -> Helium-4 + neutron.
• Powers stars; creates elements heavier than helium.
• CNO cycle in heavier stars.

Cold Fusion

• Theory of fusion at room temperature (e.g., electrolysis of heavy water).
• Controversial; most scientists are skeptical.
• Pons and Fleishman's claim was discredited due to:
  • Incorrect neutron measurements.
  • Lack of helium testing.
  • Ignoring conflicting results.
  • Lack of peer review before announcement.
• Peer review is essential for validating scientific claims.

Fission vs. Fusion

• Fission: Splitting atoms, powers nuclear plants, radioactive waste.
• Fusion: Combining atoms, powers stars, no dangerous waste, not plausible on Earth yet.