7.21 describe the role played by the control rods and moderator in the fission process

Moderator:

• Graphite is used as a moderator.
• The purpose of the moderator is to absorb some of the kinetic energy of the neutrons to slow them down.
• This is because slow neutrons are more easily absorbed by uranium 235 nuclei.

Control rods:

• Made of boron or cadmium.
• The purpose of the control rods is to absorb neutrons and completely remove them from the fission process.
• Helps adjust the rate of nuclear fission in the reactor.