1. Nuclear Fission and Fusion

2. Fission Fission means divided.
When a heavy nucleus is bombarded by neutrons the strong nuclear force weakens, but the electric repulsion remains strong.
A fast moving neutron collides with the atom and splits it into smaller fragments
High levels of energy released (7 million times the energy released by one TNT molecule!)

3. Uranium Fission Reaction
                                                                            

4. How it Works

5. Fission cont’d
One neutron starts the reaction, and an average of three neutrons are released
If these three neutrons hit other uranium atoms, they will split and 9 more neutrons are released and those will hit other atoms….
This sequence of reactions is known as a chain reaction

6. Chain Reaction

7. How it Works

8. How it Works
Imagine a sample of uranium with billions of atoms of uranium, all splitting in a chain reaction.

9. Fusion Nuclear Fusion is the opposite of fission
When two lighter nuclei must travel at high speeds to overcome repulsion and form a heavier atom
The hydrogen bomb is a destructive use of power from fusion.

10. Fusion

12. Nuclear Power Plants Nuclear power plants control these reactions
Parts of nuclear reactors…
Control rods
Fuel rods
Moderator (usually water or carbon)

13. Control Rods Made of neutron absorbing material (cadmium or boron)
Can be moved up and down and control the reaction rate

14. Fuel Rods Fuel made up of Uranium-238 and 3% Uranium-235
Uranium-238 dilute U-235 to prevent explosions

15. Moderator Moderator is kept under high pressure to prevent boiling
Moderator is used to transfer heat to other parts of power plant to generate electricity

18. Power plant simulation