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Nuclear Fission Process Explained

Overview of Nuclear Fission

• Nuclear fission occurs in fuel elements within nuclear power plants, which are typically several meters long and consist of thin fuel rods.

• Control rods can be moved up and down via a motor to manage the fission process. Fuel rods are hollow tubes containing pellets necessary for nuclear fission.

Composition of Uranium

• The enriched pellets contain approximately 5% uranium-235 and 95% uranium-238. Uranium-235 is an isotope with 92 protons and 143 neutrons.

Chain Reaction Mechanism

• When a neutron hits uranium-235, it splits into two lighter atomic nuclei, releasing 2 to 3 additional neutrons and heat that can be used to generate electricity.

• This splitting triggers a chain reaction where released neutrons continue to collide with other uranium atoms, causing further fissions—similar to a domino effect.

Conditions for Sustaining Reactions

• Specific isotopes like uranium-235 are required alongside a moderator (e.g., water) to slow down neutrons; without this moderation, sustaining the chain reaction becomes impossible due to fast-moving neutrons reducing fission probability.

Control Mechanisms in Reactors