Edexcel IGCSE Physics 7.21 Control Rods and Moderator Questions

Compare rods that absorb neutrons with moderators that slow them, and see how changing the rod position can reduce a fission reactor’s output.

Exam points

Distinguish in a reactor table: boron control rods absorb excess neutrons, while graphite or water moderators slow neutrons.
Explain that slowing neutrons in a moderator makes them more likely to cause fission.
Suggest inserting control rods to reduce reactor output when less electricity is needed.

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Some of the energy stored in the nuclei of atoms can be used to generate electricity.

A nuclear fission power station generates electricity.

State the role of the moderator in a nuclear fission power station.

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