Nuclear fission and fusion, energy from nuclear reactions

1. Nuclear Fission

1. Nuclear fission is the process where a heavy nucleus splits into two smaller nuclei, releasing a significant amount of energy.
2. Occurs when heavy elements like Uranium-235 or Plutonium-239 are bombarded with neutrons.
3. Releases neutrons, which can trigger a chain reaction.
4. Energy released is due to the mass defect and described by Einstein’s equation, E=mc².
5. Used in nuclear reactors to produce electricity and in nuclear weapons.
6. Controlled chain reactions occur in nuclear reactors, while uncontrolled reactions occur in atomic bombs.
7. Produces radioactive waste, which requires safe disposal.
8. Key example: Splitting of Uranium-235 results in nuclei like Barium and Krypton, releasing about 200 MeV of energy per fission.

2. Nuclear Fusion

1. Nuclear fusion is the process where two light nuclei combine to form a heavier nucleus, releasing a massive amount of energy.
2. Occurs at extremely high temperatures and pressures, as in the core of stars.
3. Fusion of Hydrogen isotopes (Deuterium and Tritium) produces Helium and energy.
4. Fusion reactions power the Sun and other stars.
5. Produces no radioactive waste, making it a cleaner energy source compared to fission.
6. Extremely high energy input is required to overcome the Coulomb barrier (repulsion between positively charged nuclei).
7. Fusion weapons (e.g., Hydrogen bomb) utilize fusion, initiated by a fission reaction.
8. Key reaction: Deuterium + Tritium → Helium + neutron + energy (17.6 MeV).
9. Efforts like ITER (International Thermonuclear Experimental Reactor) aim to develop practical fusion energy.

3. Energy from Nuclear Reactions

1. Nuclear reactions release energy due to the conversion of a small amount of mass into energy, as per E=mc².
2. Fission and fusion reactions produce energy millions of times greater than chemical reactions.
3. Energy from fission is used in nuclear power plants for electricity generation.
4. Fusion energy has the potential to provide virtually unlimited clean energy.
5. The binding energy per nucleon is a critical factor in determining the energy release.
6. For fission, energy comes from splitting nuclei with lower binding energy.
7. For fusion, energy comes from fusing nuclei to form a nucleus with higher binding energy.

4. Key Characteristics

1. Nuclear reactions are independent of chemical conditions or external factors like temperature and pressure.
2. Both fission and fusion release energy due to the mass defect (difference between reactant and product masses).
3. Nuclear energy is a key contributor to the global energy mix, accounting for around 10% of the world’s electricity.
4. Fusion has not yet been harnessed for commercial power production due to technological challenges.