What is the function of the moderator in a fission reactor? - Leaving Cert Physics - Question 1 - 2007

The primary function of the moderator in a fission reactor is to slow down the neutrons produced during the fission process.

By slowing down these neutrons, the moderator increases the probability of these neutrons being captured by fissile material, thereby enhancing the likelihood of further fission reactions. This process is crucial for maintaining a sustained and controlled nuclear chain reaction, which is essential for the efficient operation of a nuclear reactor.