Nuclear Fission and Nuclear Fusion: Source of Energy
ICSE · Class 12 · Physics
Complete topic list for Nuclear Fission and Nuclear Fusion: Source of Energy in ICSE Class 12 Physics. Key concepts, sub-topics, and what to focus on for board exams.
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1. Nuclear Fission
- In 1939, Hahn and Strassmann observed that when uranium nucleus with atomic number 92 was bombarded with neutrons, it split into isotopes of barium and krypton.
- Meitner and Frisch named this phenomenon nuclear fission.
- Nuclear fission is a process in which a heavy nucleus, after capturing a thermal neutron of energy 0.027 eV, splits up into two lighter nuclei of comparable masses.
2. Chain Reaction, Critical Size, and Multiplication Factor
- A chain reaction starts when neutrons produced in one fission cause further fissions.
- If more than one emitted neutron causes further fission, the reaction grows rapidly and becomes uncontrolled.
- If the reaction is controlled so that, on average, only one neutron continues the chain, the reaction remains steady.
3. Nuclear Reactor and Its Parts
- A nuclear reactor is a device in which a self-sustaining controlled chain reaction is produced in a fissionable material.
- The main fuel used is uranium enriched with U-235 or Pu-239.
- A moderator slows fast neutrons to thermal energies by elastic collisions.
4. Production of Plutonium-239 and Reactor Types
- In a reactor, neutrons not used in the fission chain reaction can be absorbed by U-238 to form U-239.
- U-239 is unstable and beta decays into Np-239.
- Np-239 also beta decays into Pu-239.
Key Concepts
Central concept: Nuclear energy from fission, fusion, and controlled chain reactions
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