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Nuclear fission reactor


The neutrons produced in a chain reaction are moving too fast to cause further fission in U235 nuclei and they have to be slowed down. This is done by graphite or heavy water and these materials are called moderators.

As the neutrons collide with atoms of the moderator they slow down from 106 ms-1 to 104 ms-1 and at this speed they are known as thermal neutrons.

Rods of boron steel are used as control rods to control the rate of the reaction since they gobble up neutrons without fissioning.

 
 
 
© Keith Gibbs 2010