Function of Moderator: The generated neutrons in the range of 1 – 100 eV have lesser possibility to absorb the U238 nuclei. The core contains a moderator (water, heavy water or graphite) to slow down the velocity of neutrons.
Function of Coolent: The heat taken from reactor by the coolent is used to convert water into steam.
Function of control Rods: Control rods which are of cadmium are used to control fission.
