Fission & Fusion | Physics for GCSE/IGCSE - Year 11 PDF Download

Nuclear Fission

• The nucleus of an atom harbors significant energy, which can be liberated through processes like nuclear fission.
• Nuclear fission entails the division of a large, unsteady nucleus into two smaller nuclei.
• Both uranium and plutonium isotopes undergo fission and serve as fuel sources in nuclear power plants.
• In the course of fission, when a neutron interacts with an unstable nucleus, it prompts the nucleus to split into two smaller nuclei, termed daughter nuclei, along with the release of two or three neutrons.
  • Additionally, gamma rays are emitted during this process.

• Following fission, the resulting products disperse rapidly.
• Energy conversion occurs from nuclear potential energy to kinetic energy.
• The mass of the products, including daughter nuclei and neutrons, is less than that of the original nucleus.
• This reduction in mass signifies the conversion of the remaining mass into energy, which is discharged during the fission event.
• Various diagrams depict the mechanisms involved in nuclear fission, offering easily comprehensible illustrations of the reaction process.
• The diagram above is useful because it shows clearly the different parts of the fission reaction
• An example of a nuclide equation for fission is:
  
• Where:
  
• The equation above depicts a fission reaction where a Uranium nucleus is bombarded with a neutron, resulting in the division into two smaller nuclei – a Krypton nucleus and a Barium nucleus – while simultaneously emitting three neutrons.
  • The sum of the top (nucleon) numbers on the left-hand side equates to the sum of the top numbers on the right-hand side: 235 + 1 = 92 + 141 + (3 × 1)
  • Similarly, the lower (proton) numbers also adhere to this principle: 92 + 0 = 36 + 56 + (3 × 0)

Nuclear Fusion

• Nuclear fusion involves the merging of two light nuclei to create a heavier nucleus.
• Sustaining extremely high temperatures is necessary for this process.
• The challenge of replicating nuclear fusion on Earth stems from this requirement.
• Stars harness nuclear fusion as an energy source.
• In many stars, hydrogen atoms undergo fusion to generate helium and release substantial energy.
  
• The energy released in nuclear fusion originates from a tiny amount of the particle's mass converting into energy.
• Mass-Energy Equivalence: Described by Albert Einstein's famous equation.
• Einstein's famous equation, E = mc²
• Signifies the energy released from fusion:
  • E = energy released from fusion in Joules (J)
  • m = mass converted into energy in kilograms (kg)
  • c = the speed of light in metres per second (m/s)
• Consequently, the mass of the resulting product (the fused nucleus) is less than the combined mass of the two initial nuclei.
  • This reduction in mass occurs due to the conversion of the remaining mass into energy, which is liberated during the fusion process.
• The energy released during nuclear fusion is immense. For instance, the energy produced from 1 kg of hydrogen undergoing fusion is equivalent to burning approximately 10 million kilograms of coal.
• This fusion reaction is visually represented as:
  
• Where: