Shielding and coolants are important parts of nuclear reactors.

Select the correct function for each of the following components of a nuclear reactor:

1. Shielding
2. Coolant

Choose from the list of functions below:

• transfers thermal energy from the reactor core
• absorbs ionizing radiation to prevent it escaping
• slows down fast-moving neutrons
• undergoes nuclear fission to release energy

Describe the process of nuclear fusion.