Nuclear Reactors and Uranium Enrichment

The fundamental reactor idea is: controlled fission chain reaction. At school level, a reactor can be understood through: **Fuel: contains fissile material. Moderator: in reactor designs that use one, slows fast neutrons to energies more suitable for sustaining fission. Control rods: absorb neutrons and regulate the chain reaction. Coolant: transfers thermal energy away from the reactor core. Shielding/containment:** reduces exposure and confines radioactive material.

Natural uranium contains different isotopes. **Uranium enrichment** increases the proportion of the fissile isotope U-235 relative to its proportion in natural uranium for reactor-fuel requirements. This chapter treats enrichment as part of understanding nuclear-reactor fuel; implementation details are not needed for learning the physics concept.

In a nuclear power plant: **nuclear energy → thermal energy → mechanical energy → electrical energy**

Conceptual criticality: **steady controlled chain reaction → approximately stable neutron population**