What is the main purpose of a moderator in a thermal nuclear reactor? A) to shield the surroundings from ionising radiations B) to decrease the number of fission chain reactions C) to decrease neutron speeds D) to prevent the core from overheating - AQA - A-Level Physics - Question 29 - 2021 - Paper 2

In a thermal nuclear reactor, a moderator's primary function is to slow down fast neutrons produced during fission reactions. By reducing the neutron speeds, the likelihood of these neutrons inducing further fission reactions increases, thereby sustaining the chain reaction necessary for the reactor's operation. This adjustment is crucial for maintaining the reactor's efficiency and safety.