Heavy-water reactor (CANDU)

For coolant in this type of reactors is used pressurized heavy water. As it is in the PWRs the cooling water from the primary circuit doesn’t drive the turbine but heats up the light water from the secondary circuit. The primary coolant heats the water from the secondary circuit in the steam generators, and due to the lower pressure it starts to boil. The produced steam is then directed to the turbine, which drives the generator for electricity production.

The main difference between the CANDU and the other types of reactors is that the heavy-water reactors use natural uranium for fuel. The fuel bundles are 10 cm in diameter and 50 cm in length, which are loaded into horizontal channels surrounded by heavy water, used for moderator. In the channels circulates pressurized heavy water (coolant). Another CANDU special feature is that they don’t have to be stopped for refueling. A refueling machine loads the new fuel from one side of the channel and discharges the spent fuel from the other during operation.