Control rods and moderators are essential components in maintaining a controlled nuclear fission chain reaction.

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

1. Control rods
2. Moderator

Choose from the list of functions below:

• absorbs excess neutrons to regulate the rate of fission
• slows down fast-moving neutrons so they are more likely to cause further fission
• transfers thermal energy from the reactor core to a steam generator
• undergoes nuclear fission to release energy and more neutrons

Describe the process of nuclear fission of a heavy nucleus such as Uranium-235, including how a chain reaction can occur.