Controlling Reactions

• How do control rods stop the chain reaction of fission going out of control?

  They absorb neutrons and ensure that the number of neutrons is low enough that a sustainable reaction is maintained
• Why must control rods be disposed as high level waste?

  They can remain radioactive for a very long time
• How does a moderator control fission reactions?

  It slows down the neutrons released to ensure they can be absorbed by a uranium nuclei to cause another reaction