2. Chain Reactions The Fission Reactor

3. Chain reactions One of the products of nuclear fission reactions are neutrons. But these are free to hit other nuclei of U-235 nearby, causing these to fission as well as releasing additional neutrons. As this process carries on, a huge amount energy is released. In fact, each generation of fission neutrons takes only a fraction of second to be produced. This is what happens in an uncontrolled chain reaction such as the nuclear bomb.

4. Chain reactions

5. Controlling chain reactions We can use control rods inserted into the uranium to slow the chain reaction down. These absorber rods contain atoms of Boron or Cadmium that can absorb the fission neutrons without undergoing a fission reaction themselves. These rods ensure that an average of one further fission occurs after every nucleus that splits. So, only one of the 2-3 neutrons produced in the fission of a nucleus will hit another U- 235 nucleus. The other(s) will be absorbed by atoms in the rods.

6. Control rods