General principles
Pressurized water reactors

The role of a nuclear boiler is to supply the steam needed to power a turbine-generator set. In a pressurized water reactor (PWR), this steam is produced in steam generators (SGs). The fluid in the primary loops, water under very high pressure, heats up as it passes through the reactor core, then gives off heat in the SGs before being recycled by pumps. As the secondary part of the SGs is at a lower pressure than the primary part, the secondary feed water to the SGs is heated to saturation and then vaporized. The steam is dried either by passing through separator-dryers or by superheating, before being sent to the turbine.