Explain what is meant by a controlled nuclear chain reaction. Your explanation should describe:

• How a chain reaction is initiated and sustained.
• The specific purpose of the moderator.
• The specific purpose of the control rods.

The energy released during fission is converted into electricity. (i) State the form of energy possessed by the fission products (daughter nuclei and neutrons) immediately after the fission reaction. (ii) State the primary useful form of energy at each of the following three stages in the power station's generation cycle:

1. Energy of the high-pressure steam driving the turbine.
2. Energy of the spinning turbine.
3. Energy transmitted through the output transmission wires.